1 /*! \page platform Platform Description
5 In order to run any simulation, SimGrid must be provided with three things:
6 something to run (i.e., your code), a description of the platform on which you
7 want to simulate your application and lastly information about the deployment
8 process: Which process should be deployed to which processor/core?
10 For the last two items, there are essentially two possible ways you can provide
11 this information as an input:
12 \li You can program it, either by using the Lua console (
13 \ref MSG_Lua_funct) or, if you're using MSG, some of MSG's platform and
14 deployment functions (\ref msg_simulation). If you want to use this,
15 check the particular documentation. (You can also check the section
16 \ref pf_flexml_bypassing, however, this documentation is deprecated;
17 there is a new, but undocumented, way to do it properly).
18 \li You can use two XML files: one contains the platform description while
19 the other contains the deployment instructions.
21 For more information on SimGrid's deployment features, please refer to
22 the \ref deployment documentation.
24 The platform description may be intricate. This documentation is all
25 about how to write this file: The basic concepts are introduced. Furthermore,
26 advanced options are explained. Additionally, some hints and tips on how to
27 write a good platform description are given.
29 \section pf_overview Some words about XML and DTD
31 We chose to use XML not only because it's extensible but also because many
32 tools (and plugins for existing tools) are available that facilitate editing and
33 validating XML files. Furthermore, libraries that parse XML are often already
34 available and very well tested.
36 The XML checking is done based on the Document Type Definition (DTD) file,
38 <a href="http://simgrid.gforge.inria.fr/simgrid.dtd">http://simgrid.gforge.inria.fr/simgrid.dtd</a>.
40 If you read the DTD, you should notice the following:
41 \li The platform tags contain a version attribute; the current version is 3.
42 This property might be used in the future to provide backwards
44 \li The DTD contains definitions for the two files used by SimGrid (i.e.,
45 platform description and deployment).
47 \section pf_basics Basic concepts
49 Nowadays, the Internet is composed of a bunch of independently managed
50 networks. Within each of those networks, there are entry and exit
51 points (most of the time, you can both enter and exit through the same
52 point); this allows to leave the current network and reach other
53 networks, possibly even in other locations.
54 At the upper level, such a network is called
55 <b>Autonomous System (AS)</b>, while at the lower level it is named
56 sub-network, or LAN (local area network).
57 They are indeed autonomous: routing is defined
58 (within the limits of his network) by the administrator, and so, those
59 networks can operate without a connection to other
60 networks. So-called gateways allow you to go from one network to
61 another, if such a (physical) connection exists. Every node in one network
62 that can be directly reached (i.e., without traversing other nodes) from
63 another network is called a gateway.
64 Each autonomous system consists of equipment such as cables (network links),
65 routers and switches as well as computers.
67 The structure of the SimGrid platform description relies exactly on the same
68 concept as a real-life platform (see above). Every resource (computers,
69 network equipment etc.) belongs to an AS, which can be defined by using the
70 \<AS\> tag. Within an AS, the routing between its elements can be defined
71 abitrarily. There are several modes for routing, and exactly one mode must be
72 selected by specifying the routing attribute in the AS tag:
75 <AS id="AS0" routing="Full">
79 Other supported values for the routing attribute can be found below, Section
82 There is also the ``<route>`` tag; this tag takes two attributes, ``src`` (source)
83 and ``dst`` (destination). Both source and destination must be valid identifiers
84 for routers (these will be introduced later). Contained by the ``<route>`` are
85 network links; these links must be used in order to communicate from the source
86 to the destination specified in the tag. Hence, a route merely describes
87 how to reach a router from another router.
90 More information and (code-)examples can be found in Section \ref pf_rm.
92 An AS can also contain itself one or more AS; this allows you to
93 model the hierarchy of your platform.
95 ### Within each AS, the following types of resources exist:
97 %Resource | Documented in Section | Description
98 --------------- | --------------------- | -----------
99 AS | | Every Autonomous System (AS) may contain one or more AS.
100 host | \ref pf_host | This entity carries out the actual computation. For this reason, it contains processors (with potentially multiple cores).
101 router | \ref pf_router | In SimGrid, routers are used to provide helpful information to routing algorithms. Routers may also act as gateways, connecting several autonomous systems with each other.
102 link | \ref pf_link | In SimGrid, (network)links define a connection between two or potentially even more resources. Every link has a bandwidth and a latency and may potentially experience congestion.
103 cluster | \ref pf_cluster | In SimGrid, clusters were introduced to model large and homogenous environments. They are not really a resource by themselves - technically, they are only a shortcut, as they will internally set up all the hosts, network and routing for you, i.e., using this resource, one can easily setup thousands of hosts and links in a few lines of code. Each cluster is itself an AS.
105 %As it is desirable to interconnect these resources, a routing has to be
106 defined. The AS is supposed to be Autonomous, hence this has to be done at the
107 AS level. The AS handles two different types of entities (<b>host/router</b>
108 and <b>AS</b>). However, the user is responsible to define routes between those resources,
109 otherwise entities will be unconnected and therefore unreachable from other
110 entities. Although several routing algorithms are built into SimGrid (see
111 \ref pf_rm), you might encounter a case where you want to define routes
112 manually (for instance, due to specific requirements of your platform).
114 There are three tags to use:
115 \li <b>ASroute</b>: to define routes between two <b>AS</b>
116 \li <b>route</b>: to define routes between two <b>host/router</b>
117 \li <b>bypassRoute</b>: to define routes between two <b>AS</b> that
118 will bypass default routing (as specified by the ``routing`` attribute
119 supplied to ``<AS>``, see above).
121 Here is an illustration of these concepts:
123 ![An illustration of an AS hierarchy. Here, AS1 contains 5 other AS' who in turn may contain other AS' as well.](AS_hierarchy.png)
124 Circles represent processing units and squares represent network routers. Bold
125 lines represent communication links. AS2 models the core of a national
126 network interconnecting a small flat cluster (AS4) and a larger
127 hierarchical cluster (AS5), a subset of a LAN (AS6), and a set of peers
128 scattered around the world (AS7).
130 \section pf_pftags Resource description
132 \subsection pf_As Platform: The \<AS\> tag
134 The concept of an AS was already outlined above (Section \ref pf_basics);
135 recall that the AS is so important because it groups other resources (such
136 as routers/hosts) together (in fact, these resources must be contained by
139 Available attributes :
141 Attribute name | Mandatory | Values | Description
142 --------------- | --------- | ------ | -----------
143 id | yes | String | The identifier of an AS; facilitates referring to this AS. ID must be unique.
144 routing | yes | Full\| Floyd\| Dijkstra\| DijkstraCache\| none\| Vivaldi\| Cluster | See Section \ref pf_rm for details.
149 <AS id="AS0" routing="Full">
150 <host id="host1" power="1000000000"/>
151 <host id="host2" power="1000000000"/>
152 <link id="link1" bandwidth="125000000" latency="0.000100"/>
153 <route src="host1" dst="host2"><link_ctn id="link1"/></route>
157 In this example, AS0 contains two hosts (host1 and host2). The route
158 between the hosts goes through link1.
160 \subsection pf_Cr Computing resources: hosts, clusters and peers.
162 \subsubsection pf_host The tag <host/>
164 A <b>host</b> represents a computer/node card. Every host is able to execute
165 code and it can send and receive data to/from other hosts. Most importantly,
166 a host can contain more than 1 core.
170 Attribute name | Mandatory | Values | Description
171 --------------- | --------- | ------ | -----------
172 id | yes | String | The identifier of the host. facilitates referring to this AS.
173 power | yes | double (must be > 0.0) | Computational power of every core of this host in FLOPS. Must be larger than 0.0.
174 core | no | int (Default: 1) | The number of cores of this host. If more than one core is specified, the "power" parameter refers to every core, i.e., the total computational power is #cores*power.<br /> If 6 cores are specified, up to 6 tasks can be executed without sharing the computational power; if more than 6 tasks are executed, computational power will be shared among these tasks. <br /> <b>Warning:</b> Although functional, this model was never scientifically assessed.
175 availability | no | int | <b>Specify if the percentage of power available.</b> (What? TODO)
176 availability_file| no | string | (Relative or absolute) filename to use as input; must contain availability traces for this host. The syntax of this file is defined below. <br /> <b>Note:</b> The filename must be specified with your system's format.
177 state | no | ON\|OFF<br/> (Default: ON) | Is this host running or not?
178 state_file | no | string | Same mechanism as availability_file.<br /> <b>Note:</b> The filename must be specified with your system's format.
179 coordinates | no | string | Must be provided when choosing the Vivaldi, coordinate-based routing model for the AS the host belongs to. More details can be found in the Section \ref pf_P2P_tags.
181 ### Possible children: ###
183 Tag name | Description | Documentation
184 ------------ | ----------- | -------------
185 <mount/> | Defines mounting points between some storage resource and the host. | \ref pf_sto_mo
186 <prop/> | The prop tag allows you to define additional information on this host following the attribute/value schema. You may want to use it to give information to the tool you use for rendering your simulation, for example. | N/A
191 <host id="host1" power="1000000000"/>
192 <host id="host2" power="1000000000">
193 <prop id="color" value="blue"/>
194 <prop id="rendershape" value="square"/>
199 \anchor pf_host_dynamism
200 ### Expressing dynamism ###
202 SimGrid provides mechanisms to change a hosts' availability over
203 time, using the ``availability_file`` attribute to the ``<host>`` tag
204 and a separate text file whose syntax is exemplified below.
206 #### Adding a trace file ####
209 <platform version="1">
210 <host id="bob" power="500000000" availability_file="bob.trace" />
214 #### Example of "bob.trace" file ####
223 Let us begin to explain this example by looking at line 2. (Line 1 will become clear soon).
224 The first column describes points in time, in this case, time 0. The second column
225 describes the relative amount of power this host is able to deliver (relative
226 to the maximum performance specified in the ``<host>`` tag). (Clearly, the
227 second column needs to contain values that are not smaller than 0 and not larger than 1).
228 In this example, our host will deliver 500 Mflop/s at time 0, as 500 Mflop/s is the
229 maximum performance of this host. At time 11.0, it will
230 deliver half of its maximum performance, i.e., 250 Mflop/s until time 20.0 when it will
231 will start delivering 80\% of its power. In this example, this amounts to 400 Mflop/s.
233 Since the periodicity in line 1 was set to be 1.0, i.e., 1 timestep, this host will
234 continue to provide 500 Mflop/s from time 21. From time 32 it will provide 250 MFlop/s and so on.
236 ### Changing initial state ###
238 It is also possible to specify whether the host is up or down by setting the
239 ``state`` attribute to either <b>ON</b> (default value) or <b>OFF</b>.
241 #### Example: Expliciting the default value "ON" ####
244 <platform version="1">
245 <host id="bob" power="500000000" state="ON" />
249 If you want this host to be unavailable, simply substitute ON with OFF.
251 ### Expressing churn ###
253 To express the fact that a host can change state over time (as in P2P
254 systems, for instance), it is possible to use a file describing the time
255 at which the host is turned on or off. An example of the content
256 of such a file is presented below.
258 #### Adding a state file ####
261 <platform version="1">
262 <host id="bob" power="500000000" state_file="bob.fail" />
266 #### Example of "bob.fail" file ####
274 A negative value means <b>down</b> (i.e., OFF) while a positive one means <b>up and
275 running</b> (i.e., ON). From time 0.0 to time 1.0, the host is on. At time 1.0, it is
276 turned off and at time 2.0, it is turned on again until time 12 (2.0 plus the
277 periodicity 10.0). It will be turned on again at time 13.0 until time 23.0, and
282 \subsubsection pf_cluster <cluster>
284 ``<cluster />`` represents a machine-cluster. It is most commonly used
285 when one wants to define many hosts and a network quickly. Technically,
286 ``cluster`` is a meta-tag: <b>from the inner SimGrid point of
287 view, a cluster is an AS where some optimized routing is defined</b>.
288 The default inner organization of the cluster is as follow:
294 ____________|__________|_____________ backbone
296 l0| l1| l2| l97| l96 | | l99
302 Here, a set of <b>host</b>s is defined. Each of them has a <b>link</b>
303 to a central backbone (backbone is a link itself, as a link can
304 be used to represent a switch, see the switch / link section
305 below for more details about it). A <b>router</b> allows to connect a
306 <b>cluster</b> to the outside world. Internally,
307 SimGrid treats a cluster as an AS containing all hosts: the router is the default
308 gateway for the cluster.
310 There is an alternative organization, which is as follows:
324 The principle is the same, except that there is no backbone. This representation
325 can be obtained easily: just do not set the bb_* attributes.
328 Attribute name | Mandatory | Values | Description
329 --------------- | --------- | ------ | -----------
330 id | yes | string | The identifier of the cluster. Facilitates referring to this cluster.
331 prefix | yes | string | Each node of the cluster has to have a name. This name will be prefixed with this prefix.
332 suffix | yes | string | Each node of the cluster will be suffixed with this suffix
333 radical | yes | string | Regexp used to generate cluster nodes name. Syntax: "10-20" will give you 11 machines numbered from 10 to 20, "10-20;2" will give you 12 machines, one with the number 2, others numbered as before. The produced number is concatenated between prefix and suffix to form machine names.
334 power | yes | int | Same as the ``power`` attribute of the ``<host>`` tag.
335 core | no | int (default: 1) | Same as the ``core`` attribute of the ``<host>`` tag.
336 bw | yes | int | Bandwidth for the links between nodes and backbone (if any). <b>See <b>link</b> section for syntax/details.</b>
337 lat | yes | int | Latency for the links between nodes and backbone (if any). See <b>link</b> section for syntax/details.
338 sharing_policy | no | string | Sharing policy for the links between nodes and backbone (if any). See <b>link</b> section for syntax/details.
339 bb_bw | no | int | Bandwidth for backbone (if any). See <b>link</b> section for syntax/details. If bb_bw and bb_lat (see below) attributes are omitted, no backbone is created (alternative cluster architecture <b>described before</b>).
340 bb_lat | no | int | Latency for backbone (if any). See <b>link</b> section for syntax/details. If bb_lat and bb_bw (see above) attributes are omitted, no backbone is created (alternative cluster architecture <b>described before</b>).
341 bb_sharing_policy | no | string | Sharing policy for the backbone (if any). See <b>link</b> section for syntax/details.
342 availability_file | no | string | Allows you to use a file as input for availability. Similar to <b>hosts</b> attribute.
343 state_file | no | string | Allows you to use a file as input for states. Similar to <b>hosts</b> attribute.
344 loopback_bw | no | int | Bandwidth for loopback (if any). See <b>link</b> section for syntax/details. If loopback_bw and loopback_lat (see below) attributes are omitted, no loopback link is created and all intra-node communication will use the main network link of the node. Loopback link is a <b>FATPIPE</b>.
345 loopback_lat | no | int | Latency for loopback (if any). See <b>link</b> section for syntax/details. See loopback_bw for more info.
346 topology | no | FLAT\|TORUS\|FAT_TREE (default: FLAT) | Network topology to use. SimGrid currently supports FLAT (with or without backbone, as described before), <a href="http://en.wikipedia.org/wiki/Torus_interconnect">TORUS </a> and FAT_TREE attributes for this tag.
347 topo_parameters | no | string | Specific parameters to pass for the topology defined in the topology tag. For torus networks, comma-separated list of the number of nodes in each dimension of the torus. For fat trees, refer to \ref AsClusterFatTree "AsClusterFatTree documentation".
351 the router name is defined as the resulting String in the following
355 router_name = prefix + clusterId + _router + suffix;
359 #### Cluster example ####
361 Consider the following two (and independent) uses of the ``cluster`` tag:
364 <cluster id="my_cluster_1" prefix="" suffix="" radical="0-262144"
365 power="1e9" bw="125e6" lat="5E-5"/>
367 <cluster id="my_cluster_2" prefix="c-" suffix=".me" radical="0-99"
368 power="1e9" bw="125e6" lat="5E-5"
369 bb_bw="2.25e9" bb_lat="5E-4"/>
372 The second example creates one router and 100 machines with the following names:
374 c-my_cluster_2_router.me
382 \subsubsection pf_peer <peer/>
384 This tag represents a peer, as in Peer-to-Peer (P2P) networks. However, internally,
385 SimGrid transforms a peer into an AS (similar to Cluster). Hence, this tag
386 is virtually only a shortcut that comes with some pre-defined resources
387 and values. These are:
389 \li A tiny AS whose routing type is cluster is created
391 \li Two links: One for download and one for upload. This is
392 convenient to use and simulate stuff under the last mile model (e.g., ADSL peers).
393 \li It connects the two links to the host
394 \li It creates a router (a gateway) that serves as an entry point for this peer zone.
395 This router has coordinates.
399 Attribute name | Mandatory | Values | Description
400 --------------- | --------- | ------ | -----------
401 id | yes | string | The identifier of the peer. Facilitates referring to this peer.
402 power | yes | int | See the description of the ``host`` tag for this attribute
403 bw_in | yes | int | Bandwidth downstream
404 bw_out | yes | int | Bandwidth upstream
405 lat | yes | double | Latency for both up- and downstream, in seconds.
406 coordinates | no | string | Coordinates of the gateway for this peer. Example value: 12.8 14.4 6.4
407 sharing_policy | no | SHARED\|FULLDUPLEX (default: FULLDUPLEX) | Sharing policy for links. See <b>link</b> description for details.
408 availability_file| no | string | Availability file for the peer. Same as host availability file. See <b>host</b> description for details.
409 state_file | no | string | State file for the peer. Same as host state file. See <b>host</b> description for details.
411 Internally, SimGrid transforms any ``<peer/>`` construct such as
414 coordinates="12.8 14.4 6.4"
420 into an ``<AS>`` (see Sections \ref pf_basics and \ref pf_As). In fact, this example of the ``<peer/>`` tag
421 is completely equivalent to the following declaration:
424 <AS id="as_FOO" routing="Cluster">
425 <host id="peer_FOO" power="1.5Gf"/>
426 <link id="link_FOO_UP" bandwidth="2.25GBps" latency="500us"/>
427 <link id="link_FOO_DOWN" bandwidth="2.25GBps" latency="500us"/>
428 <router id="router_FOO" coordinates="25.5 9.4 1.4"/>
429 <host_link id="peer_FOO" up="link_FOO_UP" down="link_FOO_DOWN"/>
434 \subsection pf_ne Network equipments: links and routers
436 There are two tags at all times available to represent network entities and
437 several other tags that are available only in certain contexts.
438 1. ``<link>``: Represents a entity that has a limited bandwidth, a
439 latency, and that can be shared according to TCP way to share this
442 The concept of links in SimGrid may not be intuitive, as links are not limited
443 to connecting (exactly) two entities; in fact, you can have more than two equipments
444 connected to it. (In graph theoretical terms: A link in SimGrid is not an edge,
447 2. ``<router/>``: Represents an entity that a message can be routed
448 to, but that is unable to execute any code. In SimGrid, routers have also
449 no impact on the performance: Routers do not limit any bandwidth nor
450 do they increase latency. As a matter of fact, routers are (almost) ignored
451 by the simulator when the simulation has begun.
453 3. ``<backbone/>``: This tag is only available when the containing AS is
454 used as a cluster (i.e., mode="Cluster")
457 If you want to represent an entity like a switch, you must use ``<link>`` (see section). Routers are used
458 to run some routing algorithm and determine routes (see Section \ref pf_routing for details).
461 \subsubsection pf_router <router/>
463 %As said before, <b>router</b> is used only to give some information
464 for routing algorithms. So, it does not have any attributes except :
468 Attribute name | Mandatory | Values | Description
469 --------------- | --------- | ------ | -----------
470 id | yes | string | The identifier of the router to be used when referring to it.
471 coordinates | yes | string | Must be provided when choosing the Vivaldi, coordinate-based routing model for the AS the router belongs to. More details can be found in the Section \ref pf_P2P_tags.
476 <router id="gw_dc1_horizdist"/>
479 \subsubsection pf_link <link>
481 Network links can represent one-hop network connections. They are
482 characterized by their id and their bandwidth; links can (but may not) be subject
487 Attribute name | Mandatory | Values | Description
488 --------------- | --------- | ------ | -----------
489 id | yes | string | The identifier of the link to be used when referring to it.
490 bandwidth | yes | int | Maximum bandwidth for this link, given in bytes/s
491 latency | no | double (default: 0.0) | Latency for this link.
492 sharing_policy | no | SHARED\|FATPIPE\|FULLDUPLEX (default: SHARED) | Sharing policy for the link.
493 state | no | ON\|OFF (default: ON) | Allows you to to turn this link on or off (working / not working)
494 bandwidth_file | no | string | Allows you to use a file as input for bandwidth.
495 latency_file | no | string | Allows you to use a file as input for latency.
496 state_file | no | string | Allows you to use a file as input for states.
499 #### Possible shortcuts for ``latency`` ####
501 When using the latency attribute, you can specify the latency by using the scientific
502 notation or by using common abbreviations. For instance, the following three tags
506 <link id="LINK1" bandwidth="125000000" latency="5E-6"/>
507 <link id="LINK1" bandwidth="125000000" latency="5us"/>
508 <link id="LINK1" bandwidth="125000000" latency="0.000005"/>
511 Here, the second tag uses "us", meaning "microseconds". Other shortcuts are:
513 Name | Abbreviation | Time (in seconds)
514 ---- | ------------ | -----------------
515 Week | w | 7 * 24 * 60 * 60
516 Day | d | 24 * 60 * 60
520 Millisecond | ms | 0.001 = 10^(-3)
521 Microsecond | us | 0.000001 = 10^(-6)
522 Nanosecond | ns | 0.000000001 = 10^(-9)
523 Picosecond | ps | 0.000000000001 = 10^(-12)
525 #### Sharing policy ####
527 By default a network link is SHARED, i.e., if two or more data flows go
528 through a link, the bandwidth is shared fairly among all data flows. This
529 is similar to the sharing policy TCP uses.
531 On the other hand, if a link is defined as a FATPIPE,
532 each flow going through this link will be provided with the complete bandwidth,
533 i.e., no sharing occurs and the bandwidth is only limiting each flow individually.
534 The complete bandwidth provided by this link in this mode
535 is ``#flows*bandwidth``, with at most ``bandwidth`` being available per flow.
537 Using the FATPIPE mode allows to model backbones that won't affect performance
540 The last mode available is FULLDUPLEX. This means that SimGrid will
541 automatically generate two links (one carrying the suffix _UP and the other the
542 suffix _DOWN) for each ``<link>`` tag. This models situations when the direction
543 of traffic is important.
546 Transfers from one side to the other will interact similarly as
547 TCP when ACK returning packets circulate on the other direction. More
548 discussion about it is available in the description of link_ctn description.
551 In other words: The SHARED policy defines a physical limit for the bandwidth.
552 The FATPIPE mode defines a limit for each application,
553 with no upper total limit.
556 Tip: By using the FATPIPE mode, you can model big backbones that
557 won't affect performance (except latency).
563 <link id="SWITCH" bandwidth="125000000" latency="5E-5" sharing_policy="FATPIPE" />
566 #### Expressing dynamism and failures ####
568 Similar to hosts, it is possible to declare links whose state, bandwidth
569 or latency changes over time (see Section \ref pf_hosts_dynamism for details).
571 In the case of network links, the ``bandwidth`` and ``latency`` attributes are
572 replaced by the ``bandwidth_file`` and ``latency_file`` attributes.
573 The following XML snippet demonstrates how to use this feature in the platform
574 file. The structure of the files "link1.bw" and "link1.lat" is shown below.
577 <link id="LINK1" state_file="link1.fail" bandwidth="80000000" latency=".0001" bandwidth_file="link1.bw" latency_file="link1.lat" />
581 Even if the syntax is the same, the semantic of bandwidth and latency
582 trace files differs from that of host availability files. For bandwidth and
583 latency, the corresponding files do not
584 express availability as a fraction of the available capacity but directly in
585 bytes per seconds for the bandwidth and in seconds for the latency. This is
586 because most tools allowing to capture traces on real platforms (such as NWS)
587 express their results this way.
590 ##### Example of "link1.bw" file #####
598 In this example, the bandwidth changes repeatedly, with all changes
599 being repeated every 12 seconds.
601 At the beginning of the the simulation, the link's bandwidth is 80,000,000
602 B/s (i.e., 80 Mb/s); this value was defined in the XML snippet above.
603 After four seconds, it drops to 40 Mb/s (line 2), and climbs
604 back to 60 Mb/s after another 4 seconds (line 3). The value does not change any
605 more until the end of the period, that is, after 12 seconds have been simulated).
606 At this point, periodicity kicks in and this behavior is repeated: Seconds
607 12-16 will experience 80 Mb/s, 16-20 40 Mb/s etc.).
609 ##### Example of "link1.lat" file #####
618 In this example, the latency varies with a period of 5 seconds.
619 In the xml snippet above, the latency is initialized to be 0.0001s (100µs). This
620 value will be kept during the first second, since the latency_file contains
621 changes to this value at second one, two and three.
622 At second one, the value will be 0.001, i.e., 1ms. One second later it will
623 be adjusted to 0.01 (or 10ms) and one second later it will be set again to 1ms. The
624 value will not change until second 5, when the periodicity defined in line 1
625 kicks in. It then loops back, starting at 100µs (the initial value) for one second.
628 #### The ``<prop/>`` tag ####
630 Similar to ``<host>``, the link may also contain the ``<prop/>`` tag; see the host
631 documentation (Section \ref pf_host) for an example.
636 \subsection pf_storage Storage
639 This is a prototype version that should evolve quickly, this
640 is just some doc valuable only at the time of writing this doc</b>
641 This section describes the storage management under SimGrid ; nowadays
642 it's only usable with MSG. It relies basically on linux-like concepts.
643 You also may want to have a look to its corresponding section in \ref
644 msg_file_management ; functions access are organized as a POSIX-like
648 \subsubsection pf_sto_conc Storage Main concepts
649 Basically there is 3 different entities to know :
650 \li the <b>storage_type</b>: here you define some kind of storage that
651 you will instantiate many type on your platform. Think of it like
652 a definition of throughput of a specific disk.
653 \li the <b>storage</b>: instance of a <b>storage_type</b>. Defines a
654 new storage of <b>storage_type</b>
655 \li the <b>mount</b>: says that the storage is located into this
658 the content of a storage has to be defined in a content file that
659 contains the content. The path to this file has to be passed within
660 the <b>content</b> attribute . Here is a way to generate it:
663 find /path/you/want -type f -exec ls -l {} \; 2>/dev/null > ./content.txt
666 \subsubsection pf_sto_sttp storage_type
669 <b>storage_type</b> attributes :
670 \li <b>id (mandatory)</b>: the identifier of the storage_type to be
671 used when referring to it.
672 \li <b>model (mandatory)</b>: Unused for now by the simulator (but
674 \li <b>content</b>: default value 0. The file containing the disk
675 content. (may be moved soon or later to <b>storage</b> tag.
677 The tag must contains some predefined model prop, as may do some other
679 <b>storage_type</b> mandatory <b>model_prop</b> :
680 \li <b>Bwrite</b>: value in B/s. Write throughput
681 \li <b>Bread</b>: value in B/s. Read throughput
682 \li <b>Bconnexion</b>: value in B/s. Connection throughput (i.e. the
683 throughput of the storage connector).
685 A storage_type can also contain the <b>prop</b> tag. The prop tag allows you
686 to define additional information on this storage_type following the
687 attribute/value schema. You may want to use it to give information to
688 the tool you use for rendering your simulation, for example.
691 <storage_type id="single_HDD" model="linear_no_lat" size="4000" content_type="txt_unix">
692 <model_prop id="Bwrite" value="30MBps" />
693 <model_prop id="Bread" value="100MBps" />
694 <model_prop id="Bconnection" value="150MBps" />
695 <b><prop id="Brand" value="Western Digital" /></b>
699 \subsubsection pf_sto_st storage
701 <b>storage_type</b> attributes :
702 \li <b>id (mandatory)</b>: the identifier of the storage to be used
703 when referring to it.
704 \li <b>typeId (mandatory)</b>: the identifier of the storage_type that
705 this storage belongs to.
706 \li <b>attach (mandatory)</b>: the host (name) to which the storage is
709 \subsubsection pf_sto_mo mount
711 <b>mount</b> attributes :
712 \li <b>id (mandatory)</b>: the id of the <b>storage</b> that must be
713 mounted on that computer.
714 \li <b>name (mandatory)</b>: the name that will be the logical
715 reference to this disk (the mount point).
717 \subsubsection pf_sto_mst mstorage
718 <b>Note : unused for now</b>
719 <b>mstorage</b> attributes :
720 \li <b>typeId (mandatory)</b>: the id of the <b>storage</b> that must
721 be mounted on that computer.
722 \li <b>name (mandatory)</b>: the name that will be the logical
723 reference to this disk (the mount point).
725 \section pf_routing Routing
727 To achieve high performance, the routing tables used within SimGrid are
728 static. This means that routing between two nodes is calculated once
729 and will not change during execution. The SimGrid team chose to use this
730 approach as it is rare to have a real deficiency of a resource;
731 most of the time, a communication fails because the links experience too much
732 congestion and hence, your connection stops before the timeout or
733 because the computer designated to be the destination of that message
736 We also chose to use shortest paths algorithms in order to emulate
737 routing. Doing so is consistent with the reality: RIP, OSPF, BGP are
738 all calculating shortest paths. They have some convergence time, but
739 at the end, so when the platform is stable (and this should be the
740 moment you want to simulate something using SimGrid) your packets will
741 follow the shortest paths.
743 \subsection pf_rm Routing models
745 Within each AS, you have to define a routing model to use. You have
746 basically 3 main kind of routing models :
748 \li Shortest-path based models: you let SimGrid calculates shortest
749 paths and manage it. Behaves more or less as most real life
751 \li Manually-entered route models: you'll have to define all routes
752 manually by yourself into the platform description file.
753 Consistent with some manually managed real life routing.
754 \li Simple/fast models: those models offers fast, low memory routing
755 algorithms. You should consider to use it if you can make some
756 assumptions about your AS. Routing in this case is more or less
759 \subsubsection pf_raf The router affair
761 Expressing routers becomes mandatory when using shortest-path based
762 models or when using ns-3 or the bindings to the GTNetS packet-level
763 simulator instead of the native analytical network model implemented
766 For graph-based shortest path algorithms, routers are mandatory,
767 because both algorithms need a graph, and so we need to have source
768 and destination for each edge.
770 Routers are naturally an important concept in GTNetS or ns-3 since the
771 way they run the packet routing algorithms is actually simulated.
772 Instead, the SimGrid’s analytical models aggregate the routing time
773 with the transfer time. Rebuilding a graph representation only from
774 the route information turns to be a very difficult task, because of
775 the missing information about how routes intersect. That is why we
776 introduced a \<router\> tag, which is simply used to express these
777 intersection points. The only attribute accepted by this tag an id. It
778 is important to understand that the \<router\> tag is only used to
779 provide topological information.
781 To express those topological information, some <b>route</b> have to be
782 defined saying which link is between which routers. Description or the
783 route syntax is given below, as well as example for the different
786 \subsubsection pf_rm_sh Shortest-path based models
788 Here is the complete list of such models, that computes routes using
789 classic shortest-paths algorithms. How to choose the best suited
790 algorithm is discussed later in the section devoted to it.
792 \li <b>Floyd</b>: Floyd routing data. Pre-calculates all routes once.
793 \li <b>Dijkstra</b>: Dijkstra routing data ,calculating routes when
795 \li <b>DijkstraCache</b>: Dijkstra routing data. Handle some cache for
796 already calculated routes.
798 All those shortest-path models are instanciated the same way. Here are
803 <AS id="AS0" routing="Floyd">
805 <cluster id="my_cluster_1" prefix="c-" suffix=""
806 radical="0-1" power="1000000000" bw="125000000" lat="5E-5"
807 router_id="router1"/>
809 <AS id="AS1" routing="none">
810 <host id="host1" power="1000000000"/>
813 <link id="link1" bandwidth="100000" latency="0.01"/>
815 <ASroute src="my_cluster_1" dst="AS1"
818 <link_ctn id="link1"/>
824 ASroute given at the end gives a topological information: link1 is
825 between router1 and host1.
829 <AS id="AS_2" routing="Dijsktra">
830 <host id="AS_2_host1" power="1000000000"/>
831 <host id="AS_2_host2" power="1000000000"/>
832 <host id="AS_2_host3" power="1000000000"/>
833 <link id="AS_2_link1" bandwidth="1250000000" latency="5E-4"/>
834 <link id="AS_2_link2" bandwidth="1250000000" latency="5E-4"/>
835 <link id="AS_2_link3" bandwidth="1250000000" latency="5E-4"/>
836 <link id="AS_2_link4" bandwidth="1250000000" latency="5E-4"/>
837 <router id="central_router"/>
838 <router id="AS_2_gateway"/>
839 <!-- routes providing topological information -->
840 <route src="central_router" dst="AS_2_host1"><link_ctn id="AS_2_link1"/></route>
841 <route src="central_router" dst="AS_2_host2"><link_ctn id="AS_2_link2"/></route>
842 <route src="central_router" dst="AS_2_host3"><link_ctn id="AS_2_link3"/></route>
843 <route src="central_router" dst="AS_2_gateway"><link_ctn id="AS_2_link4"/></route>
847 DijsktraCache example :
849 <AS id="AS_2" routing="DijsktraCache">
850 <host id="AS_2_host1" power="1000000000"/>
852 (platform unchanged compared to upper example)
855 \subsubsection pf_rm_me Manually-entered route models
857 \li <b>Full</b>: You have to enter all necessary routes manually
861 <AS id="AS0" routing="Full">
862 <host id="host1" power="1000000000"/>
863 <host id="host2" power="1000000000"/>
864 <link id="link1" bandwidth="125000000" latency="0.000100"/>
865 <route src="host1" dst="host2"><link_ctn id="link1"/></route>
869 \subsubsection pf_rm_sf Simple/fast models
871 \li <b>none</b>: No routing (Unless you know what you are doing, avoid
872 using this mode in combination with a non Constant network model).
875 <AS id="exitAS" routing="none">
876 <router id="exit_gateway"/>
879 \li <b>Vivaldi</b>: Vivaldi routing, so when you want to use
880 coordinates. See the corresponding section P2P below for details.
881 \li <b>Cluster</b>: Cluster routing, specific to cluster tag, should
882 not be used, except internally.
884 \subsection ps_dec Defining routes
886 The principle of route definition is the same for the 4 available tags
887 for doing it. Those for tags are:
889 \li <b>route</b>: to define route between host/router
890 \li <b>ASroute</b>: to define route between AS
891 \li <b>bypassRoute</b>: to bypass normal routes as calculated by the
892 network model between host/router
893 \li <b>bypassASroute</b>: same as bypassRoute, but for AS
895 Basically all those tags will contain an (ordered) list of references
896 to link that compose the route you want to define.
898 Consider the example below:
901 <route src="Alice" dst="Bob">
902 <link_ctn id="link1"/>
903 <link_ctn id="link2"/>
904 <link_ctn id="link3"/>
908 The route here from host Alice to Bob will be first link1, then link2,
909 and finally link3. What about the reverse route ? <b>route</b> and
910 <b>ASroute</b> have an optional attribute <b>symmetrical</b>, that can
911 be either YES or NO. YES means that the reverse route is the same
912 route in the inverse order, and is set to YES by default. Note that
913 this is not the case for bypass*Route, as it is more probable that you
914 want to bypass only one default route.
916 For an ASroute, things are just slightly more complicated, as you have
917 to give the id of the gateway which is inside the AS you're talking
918 about you want to access ... So it looks like this :
922 <ASroute src="AS1" dst="AS2"
923 gw_src="router1" gw_dst="router2">
924 <link_ctn id="link1"/>
928 gw == gateway, so when any message are trying to go from AS1 to AS2,
929 it means that it must pass through router1 to get out of the AS, then
930 pass through link1, and get into AS2 by being received by router2.
931 router1 must belong to AS1 and router2 must belong to AS2.
933 \subsubsection pf_linkctn link_ctn
935 a <b>link_ctn</b> is the tag that is used in order to reference a
936 <b>link</b> in a route. Its id is the link id it refers to.
938 <b>link_ctn</b> attributes :
939 \li <b>id (mandatory)</b>: Id of the link this tag refers to
940 \li <b>direction</b>: if the link referenced by <b>id</b> has been
941 declared as FULLDUPLEX, this is used to indicate in which
942 direction the route you're defining is going through this link.
943 Possible values "UP" or "DOWN".
945 \subsubsection pf_asro ASroute
947 ASroute tag purpose is to let people write manually their routes
948 between AS. It's useful when you're in Full model.
950 <b>ASroute</b> attributes :
951 \li <b>src (mandatory)</b>: the source AS id.
952 \li <b>dst (mandatory)</b>: the destination AS id.
953 \li <b>gw_src (mandatory)</b>: the gateway to be used within the AS.
954 Can be any <b>host</b> or \b router defined into the \b src AS or
955 into one of the AS it includes.
956 \li <b>gw_dst (mandatory)</b>: the gateway to be used within the AS.
957 Can be any <b>host</b> or \b router defined into the \b dst AS or
958 into one of the AS it includes.
959 \li <b>symmetrical</b>: if the route is symmetric, the reverse route
960 will be the opposite of the one defined. Can be either YES or NO,
963 <b>Example of ASroute with Full</b>
965 <AS id="AS0" routing="Full">
966 <cluster id="my_cluster_1" prefix="c-" suffix=".me"
967 radical="0-149" power="1000000000" bw="125000000" lat="5E-5"
968 bb_bw="2250000000" bb_lat="5E-4"/>
970 <cluster id="my_cluster_2" prefix="c-" suffix=".me"
971 radical="150-299" power="1000000000" bw="125000000" lat="5E-5"
972 bb_bw="2250000000" bb_lat="5E-4"/>
974 <link id="backbone" bandwidth="1250000000" latency="5E-4"/>
976 <ASroute src="my_cluster_1" dst="my_cluster_2"
977 gw_src="c-my_cluster_1_router.me"
978 gw_dst="c-my_cluster_2_router.me">
979 <link_ctn id="backbone"/>
981 <ASroute src="my_cluster_2" dst="my_cluster_1"
982 gw_src="c-my_cluster_2_router.me"
983 gw_dst="c-my_cluster_1_router.me">
984 <link_ctn id="backbone"/>
989 \subsubsection pf_ro route
990 The principle is the same as ASroute : <b>route</b> contains list of
991 links that are in the path between src and dst, except that it is for
992 routes between a src that can be either <b>host</b> or \b router and a
993 dst that can be either <b>host</b> or \b router. Useful for Full
994 as well as for the shortest-paths based models, where you
995 have to give topological information.
998 <b>route</b> attributes :
999 \li <b>src (mandatory)</b>: the source id.
1000 \li <b>dst (mandatory)</b>: the destination id.
1001 \li <b>symmetrical</b>: if the route is symmetric, the reverse route
1002 will be the opposite of the one defined. Can be either YES or NO,
1005 <b>route example in Full</b>
1007 <route src="Tremblay" dst="Bourassa">
1008 <link_ctn id="4"/><link_ctn id="3"/><link_ctn id="2"/><link_ctn id="0"/><link_ctn id="1"/><link_ctn id="6"/><link_ctn id="7"/>
1012 <b>route example in a shortest-path model</b>
1014 <route src="Tremblay" dst="Bourassa">
1018 Note that when using route to give topological information, you have
1019 to give routes with one link only in it, as SimGrid needs to know
1020 which host are at the end of the link.
1022 \subsubsection pf_byASro bypassASroute
1024 <b>Note : bypassASroute and bypassRoute are under rewriting to perform
1025 better ; so you may not use it yet</b> As said before, once you choose
1026 a model, it (if so) calculates routes for you. But maybe you want to
1027 define some of your routes, which will be specific. You may also want
1028 to bypass some routes defined in lower level AS at an upper stage :
1029 <b>bypassASroute</b> is the tag you're looking for. It allows to
1030 bypass routes defined between already defined between AS (if you want
1031 to bypass route for a specific host, you should just use byPassRoute).
1032 The principle is the same as ASroute : <b>bypassASroute</b> contains
1033 list of links that are in the path between src and dst.
1035 <b>bypassASroute</b> attributes :
1036 \li <b>src (mandatory)</b>: the source AS id.
1037 \li <b>dst (mandatory)</b>: the destination AS id.
1038 \li <b>gw_src (mandatory)</b>: the gateway to be used within the AS.
1039 Can be any <b>host</b> or \b router defined into the \b src AS or
1040 into one of the AS it includes.
1041 \li <b>gw_dst (mandatory)</b>: the gateway to be used within the AS.
1042 Can be any <b>host</b> or \b router defined into the \b dst AS or
1043 into one of the AS it includes.
1044 \li <b>symmetrical</b>: if the route is symmetric, the reverse route
1045 will be the opposite of the one defined. Can be either YES or NO,
1048 <b>bypassASroute Example</b>
1050 <bypassASRoute src="my_cluster_1" dst="my_cluster_2"
1051 gw_src="my_cluster_1_router"
1052 gw_dst="my_cluster_2_router">
1053 <link_ctn id="link_tmp"/>
1057 \subsubsection pf_byro bypassRoute
1058 <b>Note : bypassASRoute and bypassRoute are under rewriting to perform
1059 better ; so you may not use it yet</b> As said before, once you choose
1060 a model, it (if so) calculates routes for you. But maybe you want to
1061 define some of your routes, which will be specific. You may also want
1062 to bypass some routes defined in lower level AS at an upper stage :
1063 <b>bypassRoute</b> is the tag you're looking for. It allows to bypass
1064 routes defined between <b>host/router</b>. The principle is the same
1065 as route : <b>bypassRoute</b> contains list of links references of
1066 links that are in the path between src and dst.
1068 <b>bypassRoute</b> attributes :
1069 \li <b>src (mandatory)</b>: the source AS id.
1070 \li <b>dst (mandatory)</b>: the destination AS id.
1071 \li <b>symmetrical</b>: if the route is symmetric, the reverse route
1072 will be the opposite of the one defined. Can be either YES or NO,
1075 <b>bypassRoute Example</b>
1077 <bypassRoute src="host_1" dst="host_2">
1078 <link_ctn id="link_tmp"/>
1083 \subsection pb_baroex Basic Routing Example
1085 Let's say you have an AS named AS_Big that contains two other AS, AS_1
1086 and AS_2. If you want to make a host (h1) from AS_1 with another one
1087 (h2) from AS_2 then you'll have to proceed as follows:
1088 \li First, you have to ensure that a route is defined from h1 to the
1089 AS_1's exit gateway and from h2 to AS_2's exit gateway.
1090 \li Then, you'll have to define a route between AS_1 to AS_2. As those
1091 AS are both resources belonging to AS_Big, then it has to be done
1092 at AS_big level. To define such a route, you have to give the
1093 source AS (AS_1), the destination AS (AS_2), and their respective
1094 gateway (as the route is effectively defined between those two
1095 entry/exit points). Elements of this route can only be elements
1096 belonging to AS_Big, so links and routers in this route should be
1097 defined inside AS_Big. If you choose some shortest-path model,
1098 this route will be computed automatically.
1100 As said before, there are mainly 2 tags for routing :
1101 \li <b>ASroute</b>: to define routes between two <b>AS</b>
1102 \li <b>route</b>: to define routes between two <b>host/router</b>
1104 As we are dealing with routes between AS, it means that those we'll
1105 have some definition at AS_Big level. Let consider AS_1 contains 1
1106 host, 1 link and one router and AS_2 3 hosts, 4 links and one router.
1107 There will be a central router, and a cross-like topology. At the end
1108 of the crosses arms, you'll find the 3 hosts and the router that will
1109 act as a gateway. We have to define routes inside those two AS. Let
1110 say that AS_1 contains full routes, and AS_2 contains some Floyd
1111 routing (as we don't want to bother with defining all routes). As
1112 we're using some shortest path algorithms to route into AS_2, we'll
1113 then have to define some <b>route</b> to gives some topological
1114 information to SimGrid. Here is a file doing it all :
1117 <AS id="AS_Big" routing="Dijsktra">
1118 <AS id="AS_1" routing="Full">
1119 <host id="AS_1_host1" power="1000000000"/>
1120 <link id="AS_1_link" bandwidth="1250000000" latency="5E-4"/>
1121 <router id="AS_1_gateway"/>
1122 <route src="AS_1_host1" dst="AS_1_gateway">
1123 <link_ctn id="AS_1_link"/>
1126 <AS id="AS_2" routing="Floyd">
1127 <host id="AS_2_host1" power="1000000000"/>
1128 <host id="AS_2_host2" power="1000000000"/>
1129 <host id="AS_2_host3" power="1000000000"/>
1130 <link id="AS_2_link1" bandwidth="1250000000" latency="5E-4"/>
1131 <link id="AS_2_link2" bandwidth="1250000000" latency="5E-4"/>
1132 <link id="AS_2_link3" bandwidth="1250000000" latency="5E-4"/>
1133 <link id="AS_2_link4" bandwidth="1250000000" latency="5E-4"/>
1134 <router id="central_router"/>
1135 <router id="AS_2_gateway"/>
1136 <!-- routes providing topological information -->
1137 <route src="central_router" dst="AS_2_host1"><link_ctn id="AS_2_link1"/></route>
1138 <route src="central_router" dst="AS_2_host2"><link_ctn id="AS_2_link2"/></route>
1139 <route src="central_router" dst="AS_2_host3"><link_ctn id="AS_2_link3"/></route>
1140 <route src="central_router" dst="AS_2_gateway"><link_ctn id="AS_2_link4"/></route>
1142 <link id="backbone" bandwidth="1250000000" latency="5E-4"/>
1144 <ASroute src="AS_1" dst="AS_2"
1145 gw_src="AS_1_gateway"
1146 gw_dst="AS_2_gateway">
1147 <link_ctn id="backbone"/>
1152 \section pf_other_tags Tags not (directly) describing the platform
1154 There are 3 tags, that you can use inside a \<platform\> tag that are
1155 not describing the platform:
1156 \li random: it allows you to define random generators you want to use
1157 for your simulation.
1158 \li config: it allows you to pass some configuration stuff like, for
1159 example, the network model and so on. It follows the
1160 \li include: simply allows you to include another file into the
1163 \subsection pf_conf config
1164 <b>config</b> attributes :
1165 \li <b>id (mandatory)</b>: the identifier of the config to be used
1166 when referring to it.
1169 <b>config</b> tag only purpose is to include <b>prop</b> tags. Valid
1170 id are basically the same as the list of possible parameters you can
1171 use by command line, except that "/" are used for namespace
1172 definition. See the \ref options config and options page for more
1176 <b>config example</b>
1178 <?xml version='1.0'?>
1179 <!DOCTYPE platform SYSTEM "http://simgrid.gforge.inria.fr/simgrid.dtd">
1180 <platform version="3">
1181 <config id="General">
1182 <prop id="maxmin/precision" value="0.000010"></prop>
1183 <prop id="cpu/optim" value="TI"></prop>
1184 <prop id="workstation/model" value="compound"></prop>
1185 <prop id="network/model" value="SMPI"></prop>
1186 <prop id="path" value="~/"></prop>
1187 <prop id="smpi/bw_factor" value="65472:0.940694;15424:0.697866;9376:0.58729"></prop>
1190 <AS id="AS0" routing="Full">
1195 \subsection pf_rand random
1196 Not yet in use, and possibly subject to huge modifications.
1198 \subsection pf_incl include
1199 <b>include</b> tag allows to import into a file platform parts located
1200 in another file. This is done with the intention to help people
1201 combine their different AS and provide new platforms. Those files
1202 should contains XML part that contains either
1203 <b>include,cluster,peer,AS,trace,trace_connect</b> tags.
1205 <b>include</b> attributes :
1206 \li <b>file (mandatory)</b>: filename of the file to include. Possible
1207 values: absolute or relative path, syntax similar to the one in
1210 <b>Note</b>: due to some obscure technical reasons, you have to open
1211 and close tag in order to let it work.
1212 <b>include Example</b>
1214 <?xml version='1.0'?>
1215 <!DOCTYPE platform SYSTEM "http://simgrid.gforge.inria.fr/simgrid.dtd">
1216 <platform version="3">
1217 <AS id="main" routing="Full">
1218 <include file="clusterA.xml"></include>
1219 <include file="clusterB.xml"></include>
1224 \subsection pf_tra trace and trace_connect
1225 Both tags are an alternate way to passe availability, state, and so on
1226 files to entity. Instead of referring to the file directly in the host,
1227 link, or cluster tag, you proceed by defining a trace with an id
1228 corresponding to a file, later a host/link/cluster, and finally using
1229 trace_connect you say that the file trace must be used by the entity.
1230 Get it ? Let's have a look at an example :
1233 <AS id="AS0" routing="Full">
1234 <host id="bob" power="1000000000"/>
1236 <trace id="myTrace" file="bob.trace" periodicity="1.0"/>
1237 <trace_connect trace="myTrace" element="bob" kind="POWER"/>
1240 All constraints you have is that <b>trace_connect</b> is after
1241 <b>trace</b> and <b>host</b> definitions.
1244 <b>trace</b> attributes :
1245 \li <b>id (mandatory)</b>: the identifier of the trace to be used when
1247 \li <b>file</b>: filename of the file to include. Possible values :
1248 absolute or relative path, syntax similar to the one in use on
1249 your system. If omitted, the system expects that you provide the
1250 trace values inside the trace tags (see below).
1251 \li <b>trace periodicity (mandatory)</b>: trace periodicity, same
1252 definition as in hosts (see upper for details).
1254 Here is an example of trace when no file name is provided:
1257 <trace id="myTrace" periodicity="1.0">
1264 <b>trace_connect</b> attributes :
1265 \li <b>kind</b>: the type of trace, possible values
1266 <b>HOST_AVAIL|POWER|LINK_AVAIL|BANDWIDTH|LATENCY,</b> default:
1268 \li <b>trace (mandatory)</b>: the identifier of the trace referenced.
1269 \li <b>element (mandatory)</b>: the identifier of the entity referenced.
1273 \section pf_hints Hints and tips, or how to write a platform efficiently
1275 Now you should know at least the syntax and be able to create a
1276 platform by your own. However, after having ourselves wrote some platforms, there
1277 are some best practices you should pay attention to in order to
1278 produce good platform and some choices you can make in order to have
1279 faster simulations. Here's some hints and tips, then.
1281 \subsection pf_as_h AS Hierarchy
1282 The AS design allows SimGrid to go fast, because computing route is
1283 done only for the set of resources defined in this AS. If you're using
1284 only a big AS containing all resource with no AS into it and you're
1285 using Full model, then ... you'll loose all interest into it. On the
1286 other hand, designing a binary tree of AS with, at the lower level,
1287 only one host, then you'll also loose all the good AS hierarchy can
1288 give you. Remind you should always be "reasonable" in your platform
1289 definition when choosing the hierarchy. A good choice if you try to
1290 describe a real life platform is to follow the AS described in
1291 reality, since this kind of trade-off works well for real life
1294 \subsection pf_exit_as Exit AS: why and how
1295 Users that have looked at some of our platforms may have notice a
1296 non-intuitive schema ... Something like that :
1300 <AS id="AS_4" routing="Full">
1301 <AS id="exitAS_4" routing="Full">
1302 <router id="router_4"/>
1304 <cluster id="cl_4_1" prefix="c_4_1-" suffix="" radical="1-20" power="1000000000" bw="125000000" lat="5E-5" bb_bw="2250000000" bb_lat="5E-4"/>
1305 <cluster id="cl_4_2" prefix="c_4_2-" suffix="" radical="1-20" power="1000000000" bw="125000000" lat="5E-5" bb_bw="2250000000" bb_lat="5E-4"/>
1306 <link id="4_1" bandwidth="2250000000" latency="5E-5"/>
1307 <link id="4_2" bandwidth="2250000000" latency="5E-5"/>
1308 <link id="bb_4" bandwidth="2250000000" latency="5E-4"/>
1309 <ASroute src="cl_4_1"
1311 gw_src="c_4_1-cl_4_1_router"
1312 gw_dst="c_4_2-cl_4_2_router"
1314 <link_ctn id="4_1"/>
1315 <link_ctn id="bb_4"/>
1316 <link_ctn id="4_2"/>
1318 <ASroute src="cl_4_1"
1320 gw_src="c_4_1-cl_4_1_router"
1323 <link_ctn id="4_1"/>
1324 <link_ctn id="bb_4"/>
1326 <ASroute src="cl_4_2"
1328 gw_src="c_4_2-cl_4_2_router"
1331 <link_ctn id="4_2"/>
1332 <link_ctn id="bb_4"/>
1337 In the AS_4, you have an exitAS_4 defined, containing only one router,
1338 and routes defined to that AS from all other AS (as cluster is only a
1339 shortcut for an AS, see cluster description for details). If there was
1340 an upper AS, it would define routes to and from AS_4 with the gateway
1341 router_4. It's just because, as we did not allowed (for performances
1342 issues) to have routes from an AS to a single host/router, you have to
1343 enclose your gateway, when you have AS included in your AS, within an
1344 AS to define routes to it.
1346 \subsection pf_P2P_tags P2P or how to use coordinates
1347 SimGrid allows you to use some coordinated-based system, like vivaldi,
1348 to describe a platform. The main concept is that you have some peers
1349 that are located somewhere: this is the function of the
1350 <b>coordinates</b> of the \<peer\> or \<host\> tag. There's nothing
1351 complicated in using it, here is an example of it:
1354 <?xml version='1.0'?>
1355 <!DOCTYPE platform SYSTEM "http://simgrid.gforge.inria.fr/simgrid.dtd">
1356 <platform version="3">
1358 <config id="General">
1359 <prop id="network/coordinates" value="yes"></prop>
1361 <AS id="AS0" routing="Vivaldi">
1362 <host id="100030591" coordinates="25.5 9.4 1.4" power="1500000000.0" />
1363 <host id="100036570" coordinates="-12.7 -9.9 2.1" power="730000000.0" />
1365 <host id="100429957" coordinates="17.5 6.7 18.8" power="830000000.0" />
1370 Coordinates are then used to calculate latency between two hosts by
1371 calculating the euclidean distance between the two hosts coordinates.
1372 The results express the latency in ms.
1374 Note that the previous example defines a routing directly between hosts but it could be also used to define a routing between AS.
1375 That is for example what is commonly done when using peers (see Section \ref pf_peer).
1377 <?xml version='1.0'?>
1378 <!DOCTYPE platform SYSTEM "http://simgrid.gforge.inria.fr/simgrid.dtd">
1379 <platform version="3">
1381 <config id="General">
1382 <prop id="network/coordinates" value="yes"></prop>
1384 <AS id="AS0" routing="Vivaldi">
1385 <peer id="peer-0" coordinates="173.0 96.8 0.1" power="730Mf" bw_in="13.38MBps" bw_out="1.024MBps" lat="500us"/>
1386 <peer id="peer-1" coordinates="247.0 57.3 0.6" power="730Mf" bw_in="13.38MBps" bw_out="1.024MBps" lat="500us" />
1387 <peer id="peer-2" coordinates="243.4 58.8 1.4" power="730Mf" bw_in="13.38MBps" bw_out="1.024MBps" lat="500us" />
1391 In such a case though, we connect the AS created by the <b>peer</b> tag with the Vivaldi routing mechanism.
1392 This means that to route between AS1 and AS2, it will use the coordinates of router_AS1 and router_AS2.
1393 This is currently a convention and we may offer to change this convention in the DTD later if needed.
1394 You may have noted that conveniently, a peer named FOO defines an AS named FOO and a router named router_FOO, which is why it works seamlessly with the <b>peer</b> tag.
1397 \subsection pf_wisely Choosing wisely the routing model to use
1400 Choosing wisely the routing model to use can significantly fasten your
1401 simulation/save your time when writing the platform/save tremendous
1402 disk space. Here is the list of available model and their
1403 characteristics (lookup : time to resolve a route):
1405 \li <b>Full</b>: Full routing data (fast, large memory requirements,
1407 \li <b>Floyd</b>: Floyd routing data (slow initialization, fast
1408 lookup, lesser memory requirements, shortest path routing only).
1409 Calculates all routes at once at the beginning.
1410 \li <b>Dijkstra</b>: Dijkstra routing data (fast initialization, slow
1411 lookup, small memory requirements, shortest path routing only).
1412 Calculates a route when necessary.
1413 \li <b>DijkstraCache</b>: Dijkstra routing data (fast initialization,
1414 fast lookup, small memory requirements, shortest path routing
1415 only). Same as Dijkstra, except it handles a cache for latest used
1417 \li <b>none</b>: No routing (usable with Constant network only).
1418 Defines that there is no routes, so if you try to determine a
1419 route without constant network within this AS, SimGrid will raise
1421 \li <b>Vivaldi</b>: Vivaldi routing, so when you want to use coordinates
1422 \li <b>Cluster</b>: Cluster routing, specific to cluster tag, should
1425 \subsection pf_switch Hey, I want to describe a switch but there is no switch tag !
1427 Actually we did not include switch tag, ok. But when you're trying to
1428 simulate a switch, the only major impact it has when you're using
1429 fluid model (and SimGrid uses fluid model unless you activate GTNetS,
1430 ns-3, or constant network mode) is the impact of the upper limit of
1431 the switch motherboard speed that will eventually be reached if you're
1432 using intensively your switch. So, the switch impact is similar to a
1433 link one. That's why we are used to describe a switch using a link tag
1434 (as a link is not an edge by a hyperedge, you can connect more than 2
1437 \subsection pf_platform_multipath How to express multipath routing in platform files?
1439 It is unfortunately impossible to express the fact that there is more
1440 than one routing path between two given hosts. Let's consider the
1441 following platform file:
1444 <route src="A" dst="B">
1447 <route src="B" dst="C">
1450 <route src="A" dst="C">
1455 Although it is perfectly valid, it does not mean that data traveling
1456 from A to C can either go directly (using link 3) or through B (using
1457 links 1 and 2). It simply means that the routing on the graph is not
1458 trivial, and that data do not following the shortest path in number of
1459 hops on this graph. Another way to say it is that there is no implicit
1460 in these routing descriptions. The system will only use the routes you
1461 declare (such as <route src="A" dst="C"><link_ctn
1462 id="3"/></route>), without trying to build new routes by aggregating
1465 You are also free to declare platform where the routing is not
1466 symmetric. For example, add the following to the previous file:
1469 <route src="C" dst="A">
1475 This makes sure that data from C to A go through B where data from A
1476 to C go directly. Don't worry about realism of such settings since
1477 we've seen ways more weird situation in real settings (in fact, that's
1478 the realism of very regular platforms which is questionable, but
1479 that's another story).
1481 \section pf_flexml_bypassing Bypassing the XML parser with your own C functions
1482 <b>NOTE THAT THIS DOCUMENTATION, WHILE STILL WORKING, IS STRONGLY DEPRECATED</b>
1484 So you want to bypass the XML files parser, uh? Maybe doing some parameter
1485 sweep experiments on your simulations or so? This is possible, and
1486 it's not even really difficult (well. Such a brutal idea could be
1487 harder to implement). Here is how it goes.
1489 For this, you have to first remember that the XML parsing in SimGrid is done
1490 using a tool called FleXML. Given a DTD, this gives a flex-based parser. If
1491 you want to bypass the parser, you need to provide some code mimicking what
1492 it does and replacing it in its interactions with the SURF code. So, let's
1493 have a look at these interactions.
1495 FleXML parser are close to classical SAX parsers. It means that a
1496 well-formed SimGrid platform XML file might result in the following
1499 - start "platform_description" with attribute version="2"
1500 - start "host" with attributes id="host1" power="1.0"
1502 - start "host" with attributes id="host2" power="2.0"
1504 - start "link" with ...
1506 - start "route" with ...
1507 - start "link_ctn" with ...
1510 - end "platform_description"
1512 The communication from the parser to the SURF code uses two means:
1513 Attributes get copied into some global variables, and a surf-provided
1514 function gets called by the parser for each event. For example, the event
1515 - start "host" with attributes id="host1" power="1.0"
1517 let the parser do something roughly equivalent to:
1519 strcpy(A_host_id,"host1");
1524 In SURF, we attach callbacks to the different events by initializing the
1525 pointer functions to some the right surf functions. Since there can be
1526 more than one callback attached to the same event (if more than one
1527 model is in use, for example), they are stored in a dynar. Example in
1528 workstation_ptask_L07.c:
1530 /* Adding callback functions */
1531 surf_parse_reset_parser();
1532 surfxml_add_callback(STag_surfxml_host_cb_list, &parse_cpu_init);
1533 surfxml_add_callback(STag_surfxml_prop_cb_list, &parse_properties);
1534 surfxml_add_callback(STag_surfxml_link_cb_list, &parse_link_init);
1535 surfxml_add_callback(STag_surfxml_route_cb_list, &parse_route_set_endpoints);
1536 surfxml_add_callback(ETag_surfxml_link_c_ctn_cb_list, &parse_route_elem);
1537 surfxml_add_callback(ETag_surfxml_route_cb_list, &parse_route_set_route);
1539 /* Parse the file */
1540 surf_parse_open(file);
1541 xbt_assert(!surf_parse(), "Parse error in %s", file);
1545 So, to bypass the FleXML parser, you need to write your own version of the
1546 surf_parse function, which should do the following:
1547 - Fill the A_<tag>_<attribute> variables with the wanted values
1548 - Call the corresponding STag_<tag>_fun function to simulate tag start
1549 - Call the corresponding ETag_<tag>_fun function to simulate tag end
1550 - (do the same for the next set of values, and loop)
1552 Then, tell SimGrid that you want to use your own "parser" instead of the stock one:
1554 surf_parse = surf_parse_bypass_environment;
1555 MSG_create_environment(NULL);
1556 surf_parse = surf_parse_bypass_application;
1557 MSG_launch_application(NULL);
1560 A set of macros are provided at the end of
1561 include/surf/surfxml_parse.h to ease the writing of the bypass
1562 functions. An example of this trick is distributed in the file
1563 examples/msg/masterslave/masterslave_bypass.c