you could also get in real settings to not hinder the realism of your
simulation.
-\verbatim
+\code
double get_host_load() {
m_task_t task = MSG_task_create("test", 0.001, 0, NULL);
double date = MSG_get_clock();
MSG_task_destroy(task);
return (0.001/date);
}
-\endverbatim
+\endcode
Of course, it may not match your personal definition of "host load". In this
case, please detail what you mean on the mailing list, and we will extend
ready). However, getting the *real* communication time is not really
hard either. The following solution is a good starting point.
-\verbatim
+\code
int sender()
{
m_task_t task = MSG_task_create("Task", task_comp_size, task_comm_size,
MSG_task_destroy(task);
return 0;
}
-\endverbatim
+\endcode
\subsection faq_MIA_SimDag SimDag related questions
create 3 SD_tasks: t1, t2 and c and add dependencies in the following
way:
-\verbatim
+\code
SD_task_dependency_add(NULL, NULL, t1, c);
SD_task_dependency_add(NULL, NULL, c, t2);
-\endverbatim
+\endcode
This way task t2 cannot start before the termination of communication c
which in turn cannot start before t1 ends.
distributed. Here is an example of how you could do that. Assume T1
has to be done before T2.
-\verbatim
+\code
int your_agent(int argc, char *argv[] {
...
T1 = MSG_task_create(...);
}
}
}
-\endverbatim
+\endcode
If you decide that the distributed part is not that much important and that
DAG is really the level of abstraction you want to work with, then you should
\subsection faq_MIA_generic Generic features
-\subsubsection faq_more_processes Increasing the amount of simulated processes
-
-Here are a few tricks you can apply if you want to increase the amount
-of processes in your simulations.
-
- - <b>A few thousands of simulated processes</b> (soft tricks)\n
- SimGrid can use either pthreads library or the UNIX98 contexts. On
- most systems, the number of pthreads is limited and then your
- simulation may be limited for a stupid reason. This is especially
- true with the current linux pthreads, and I cannot get more than
- 2000 simulated processes with pthreads on my box. The UNIX98
- contexts allow me to raise the limit to 25,000 simulated processes
- on my laptop.\n\n
- The <tt>--with-context</tt> option of the <tt>./configure</tt>
- script allows you to choose between UNIX98 contexts
- (<tt>--with-context=ucontext</tt>) and the pthread version
- (<tt>--with-context=pthread</tt>). The default value is ucontext
- when the script detect a working UNIX98 context implementation. On
- Windows boxes, the provided value is discarded and an adapted
- version is picked up.\n\n
- We experienced some issues with contexts on some rare systems
- (solaris 8 and lower or old alpha linuxes comes to mind). The main
- problem is that the configure script detect the contexts as being
- functional when it's not true. If you happen to use such a system,
- switch manually to the pthread version, and provide us with a good
- patch for the configure script so that it is done automatically ;)
-
- - <b>Hundred thousands of simulated processes</b> (hard-core tricks)\n
- As explained above, SimGrid can use UNIX98 contexts to represent
- and handle the simulated processes. Thanks to this, the main
- limitation to the number of simulated processes becomes the
- available memory.\n\n
- Here are some tricks I had to use in order to run a token ring
- between 25,000 processes on my laptop (1Gb memory, 1.5Gb swap).\n
- - First of all, make sure your code runs for a few hundreds
- processes before trying to push the limit. Make sure it's
- valgrind-clean, i.e. that valgrind does not report neither memory
- error nor memory leaks. Indeed, numerous simulated processes
- result in *fat* simulation hindering debugging.
- - It was really boring to write 25,000 entries in the deployment
- file, so I wrote a little script
- <tt>examples/gras/mutual_exclusion/simple_token/make_deployment.pl</tt>, which you may
- want to adapt to your case. You could also think about hijacking
- the SURFXML parser (have look at \ref pf_flexml_bypassing).
- - The deployment file became quite big, so I had to do what is in
- the FAQ entry \ref faq_flexml_limit
- - Each UNIX98 context has its own stack entry. As debugging this is
- quite hairy, the default value is a bit overestimated so that
- user doesn't get into trouble about this. You want to tune this
- size to increase the number of processes. This is the
- <tt>STACK_SIZE</tt> define in
- <tt>src/xbt/xbt_context_sysv.c</tt>, which is 128kb by default.
- Reduce this as much as you can, but be warned that if this value
- is too low, you'll get a segfault. The token ring example, which
- is quite simple, runs with 40kb stacks.
- - You may tweak the logs to reduce the stack size further. When
- logging something, we try to build the string to display in a
- char array on the stack. The size of this array is constant (and
- equal to XBT_LOG_BUFF_SIZE, defined in include/xbt/log/h). If the
- string is too large to fit this buffer, we move to a dynamically
- sized buffer. In which case, we have to traverse one time the log
- event arguments to compute the size we need for the buffer,
- malloc it, and traverse the argument list again to do the actual
- job.\n
- The idea here is to move XBT_LOG_BUFF_SIZE to 1, forcing the logs
- to use a dynamic array each time. This allows us to lower further
- the stack size at the price of some performance loss...\n
- This allowed me to run the reduce the stack size to ... 4k. Ie,
- on my 1Gb laptop, I can run more than 250,000 processes!
-
\subsubsection faq_MIA_batch_scheduler Is there a native support for batch schedulers in SimGrid?
No, there is no native support for batch schedulers and none is
file that highlights the most important changes) even before you
upgrade your copy of SimGrid, too.
-Backward compatibility is very important to us, as we want to provide
-a scientific tool allowing to evaluate the code you write in several
-years, too. That being said, we sometimes change the interface to make
-them more usable to the users. When we do so, we always keep the old
-interface as DEPRECATED. If you still want to use them, you want to
-define the SIMGRID_DEPRECATED preprocessor symbol before loading the
-SimGrid files:
-
-@verbatim
-#define SIMGRID_DEPRECATED
-#include <msg/msg.h>
-@endverbatim
+We do our best to maintain the backward compatibility, but we
+sometimes have to fix the things that are too broken. If we happen to
+kill a feature that you were using, we are sorry. We think that you
+should update to the new way of doing things, but if you can't afford
+it, that's ok. Just stick to the last version that were working for
+you, and have a pleasant day.
\subsection faq_trouble_lib_compil SimGrid compilation and installation problems
We know only one reason for the configure to fail:
- <b>You are using a broken build environment</b>\n
- If symptom is that the configury magic complains about gcc not being able to build
- executables, you are probably missing the libc6-dev package. Damn Ubuntu.
+ Try updating your cmake version. If symptom is that the configury
+ magic complains about gcc not being able to build executables, you
+ are probably missing the libc6-dev package. Damn Ubuntu.
If you experience other kind of issue, please get in touch with us. We are
always interested in improving our portability to new systems.
quite impossible that you see this message when doing dynamic linking.
If you compile your code statically (and if you use a pthread version
-of SimGrid -- see \ref faq_more_processes), you must absolutely
+of SimGrid), you must absolutely
specify <tt>-lpthread</tt> on the linker command line. As usual, this should
come after <tt>-lsimgrid</tt> on this command line.
-\subsubsection faq_trouble_lib_msg_deprecated "gcc: undefined reference to MSG_*"
-
-Since version 3.7 all the m_channel_t mecanism is deprecated. So functions
-about this mecanism may get removed in future releases.
-
-List of functions:
-
-\li XBT_PUBLIC(int) MSG_get_host_number(void);
-
-\li XBT_PUBLIC(m_host_t *) MSG_get_host_table(void);
-
-\li XBT_PUBLIC(MSG_error_t) MSG_get_errno(void);
-
-\li XBT_PUBLIC(MSG_error_t) MSG_task_get(m_task_t * task, m_channel_t channel);
-
-\li XBT_PUBLIC(MSG_error_t) MSG_task_get_with_timeout(m_task_t * task, m_channel_t channel, double max_duration);
-
-\li XBT_PUBLIC(MSG_error_t) MSG_task_get_from_host(m_task_t * task, int channel, m_host_t host);
-
-\li XBT_PUBLIC(MSG_error_t) MSG_task_get_ext(m_task_t * task, int channel, double max_duration, m_host_t host);
-
-\li XBT_PUBLIC(MSG_error_t) MSG_task_put(m_task_t task, m_host_t dest, m_channel_t channel);
-
-\li XBT_PUBLIC(MSG_error_t) MSG_task_put_bounded(m_task_t task, m_host_t dest, m_channel_t channel, double max_rate);
-
-\li XBT_PUBLIC(MSG_error_t) MSG_task_put_with_timeout(m_task_t task, m_host_t dest, m_channel_t channel, double max_duration);
-
-\li XBT_PUBLIC(int) MSG_task_Iprobe(m_channel_t channel);
-
-\li XBT_PUBLIC(int) MSG_task_probe_from(m_channel_t channel);
-
-\li XBT_PUBLIC(int) MSG_task_probe_from_host(int channel, m_host_t host);
-
-\li XBT_PUBLIC(MSG_error_t) MSG_set_channel_number(int number);
-
-\li XBT_PUBLIC(int) MSG_get_channel_number(void);
-
-If you want them you have to compile Simgrid v3.7 with option "-Denable_msg_deprecated=ON".
-Using them should print warning to inform what new function you have to use.
-
\subsection faq_trouble_errors Runtime error messages
\subsubsection faq_flexml_limit "surf_parse_lex: Assertion `next limit' failed."
If your files are too old, you can use the simgrid_update_xml.pl
script which can be found in the tools directory of the archive.
+\subsection faq_trouble_debug Debugging SMPI applications
+
+In order to debug SMPI programs, you can use the following options:
+
+- <b>-wrapper 'gdb --args'</b>: this option is used to use a wrapper
+ in order to call the SMPI process. Good candidates for this options
+ are "gdb --args", "valgrind", "rr record", "strace", etc;
+
+- <b>-foreground</b>: this options gives the debugger access to the terminal
+ which is needed in order to use an interactive debugger.
+
+Both options are needed in order to run the SMPI process under GDB.
+
\subsection faq_trouble_valgrind Valgrind-related and other debugger issues
If you don't, you really should use valgrind to debug your code, it's
on your side... We have plenty of FAQ entries to redact and new
features to implement for the impenitents! ;)
+Using
+
\subsection faq_surf_network_latency I get weird timings when I play with the latencies.
OK, first of all, remember that units should be Bytes, Flops and
