/*! \page faq Frequently Asked Questions
-\htmlinclude FAQ.toc
+\htmlinclude .FAQ.doc.toc
\section faq_installation Installing the SimGrid library
version are available. Here is what you can find if you try a <tt>ls
/home/joe/lib</tt>:
-\verbatim libsimgrid.a libsimgrid.la libsimgrid.so libsimgrid.so.0 libsimgrid.so.0.0.1
+\verbatim libsimgrid.a libsimgrid.la libsimgrid.so libsimgrid.so.0 libsimgrid.so.0.0.1
\endverbatim
Thus, there is two ways to link your program with SimGrid:
to gforge so people that are interested by helping on this part will
have the possibility to do it.
-\subsection faq_SG_DAG How to implement a distributed dynamic scheduler of DAGs without the SG module?
+\subsection faq_SG_DAG How to implement a distributed dynamic scheduler of DAGs.
Distributed is somehow "contagious". If you start making distributed
decisions, there is no way to handle DAGs directly anymore (unless I am
missing something). You have to encode your DAGs in term of communicating
process to make the whole scheduling process distributed. Believe me, it is
worth the effort since you'll then be able to try your algorithms in a very
-wide variety of conditions.
+wide variety of conditions. Here is an example of how you could do that.
+Assume T1 has to be done before T2.
+\verbatim
+ int your_agent(int argc, char *argv[] {
+ ...
+ T1 = MSG_task_create(...);
+ T2 = MSG_task_create(...);
+ ...
+ while(1) {
+ ...
+ if(cond) MSG_task_execute(T1);
+ ...
+ if((MSG_task_get_remaining_computation(T1)=0.0) && (you_re_in_a_good_mood))
+ MSG_task_execute(T2)
+ else {
+ /* do something else */
+ }
+ }
+ }
+\endverbatim
+
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 (but it
prevents you from having "realistic" platform modeling), then you should
Note however that SURF will be slower than the old SG to handle traces with
a lots of variations (there is no trace integration anymore).
+\subsection faq_SG_future Will SG come back in the maintained branch one day?
+
+Sure. In fact, we already have thought about a new and cleaner API:
+\verbatim
+void* SG_link_get_data(SG_link_t link);
+void SG_link_set_data(SG_link_t link, void *data);
+const char* SG_link_get_name(SG_link_t link);
+double SG_link_get_capacity(SG_link_t link);
+double SG_link_get_current_bandwidth(SG_link_t link);
+double SG_link_get_current_latency(SG_link_t link);
+
+SG_workstation_t SG_workstation_get_by_name(const char *name);
+SG_workstation_t* SG_workstation_get_list(void);
+int SG_workstation_get_number(void);
+void SG_workstation_set_data(SG_workstation_t workstation, void *data);
+void * SG_workstation_get_data(SG_workstation_t workstation);
+const char* SG_workstation_get_name(SG_workstation_t workstation);
+SG_link_t* SG_workstation_route_get_list(SG_workstation_t src, SG_workstation_t dst);
+int SG_workstation_route_get_size(SG_workstation_t src, SG_workstation_t dst);
+double SG_workstation_get_power(SG_workstation_t workstation);
+double SG_workstation_get_available_power(SG_workstation_t workstation);
+
+SG_task_t SG_task_create(const char *name, void *data, double amount);
+int SG_task_schedule(SG_task_t task, int workstation_nb,
+ SG_workstation_t **workstation_list, double *computation_amount,
+ double *communication_amount, double rate);
+
+void* SG_task_get_data(SG_task_t task);
+void SG_task_set_data(SG_task_t task, void *data);
+const char* SG_task_get_name(SG_task_t task);
+double SG_task_get_amount(SG_task_t task);
+double SG_task_get_remaining_amount(SG_task_t task);
+void SG_task_dependency_add(const char *name, void *data, SG_task_t src, SG_task_t dst);
+void SG_task_dependency_remove(SG_task_t src, SG_task_t dst);
+e_SG_task_state_t SG_task_state_get(SG_task_t task); /* e_SG_task_state_t can be either SG_SCHEDULED, SG_RUNNING, SG_DONE, or SG_FAILED */
+void SG_task_watch(SG_task_t task, e_SG_task_state_t state); /* SG_simulate will stop as soon as the state of this task is the one given in argument.
+ Watch-point is then automatically removed */
+void SG_task_unwatch(SG_task_t task, e_SG_task_state_t state);
+
+void SG_task_unschedule(SG_task_t task); /* change state and rerun.. */
+
+SG_task_t *SG_simulate(double how_long); /* returns a NULL-terminated array of SG_task_t whose state has changed */
+\endverbatim
+
+We're just looking for somebody to implement it... :)
+
\section faq_dynamic Dynamic resources and platform building
\subsection faq_platform Building a realistic platform
bandwidth_file and latency_file do not express fraction of available
power but are expressed directly in Mb/s and seconds.
-\subsection faq_flexml_bypassing How could I have some C functions do what the platform and deployment files do?
+\subsection faq_flexml_bypassing How can I have some C functions do what the platform file does?
So you want to bypass the XML files parser, uh? Maybe doin some parameter
sweep experiments on your simulations or so? This is possible, but it's not
\section faq_troubleshooting Troubleshooting
+\subsection faq_distcheck_fails Dude! "make check" fails on my machine!
+
+Don't assume we never run this target, because we do. Really. Promise!
+
+There is several reasons which may cause the make check to fail on your
+machine:
+
+ - <b>You are using a borken compiler</b>.\n
+ The symptom may be that the "make check" fails within testsuite/gras
+ directory.\n
+ For example, the breezy release of Ubuntu comes with a prerelease of the
+ 4.0 gcc compiler. This version happens to be completely unusable, and you
+ should install a gcc-3.4 compiler and change the /usr/bin/gcc link to let
+ it point on /usr/bin/gcc-3.4.
+ - <b>You are using a borken libc (probably concerning the contextes)</b>.\n
+ The symptom is that the "make check" fails within the examples/msg directory.\n
+ By default, SimGrid uses something called ucontexts. This is part of the
+ libc, but it's quite undertested. For example, some (old) versions of the
+ glibc on alpha do not implement these functions, but provide the stubs
+ (which return ENOSYS: not implemented). It fools our detection mecanism
+ and leads to segfaults.\n
+ On some x86_64, the pointer to function is stored into a integer, but int
+ are 32bits only on this arch while pointers are 64bits. Our detection
+ mecanism also fails to detect the problem, which leads to segfaults.\n
+ In both cases, there is not much we can do to fix the bug. We are working
+ on a workaround for x86_64 machines, but in the meanwhile, you can
+ compile with --with-context=pthread to avoid ucontext completely. You'll
+ be a bit more limitated in the number of simulated processes you can start
+ concurently, but 5000 processes is still enough for most purposes, isn't
+ it?\n
+ This limitation is the reason why we insist on using this piece of ...
+ software even if it's so troublesome.
+ - <b>There is a bug in SimGrid we aren't aware of</b>.\n
+ If none of the above apply, please drop us a mail on the mailing list so
+ that we can check it out.
+
\subsection faq_context_1000 I want thousands of simulated processes
SimGrid can use either pthreads library or the UNIX98 contextes. On most
adapted version is picked up.
We experienced some issues with contextes on some rare systems (solaris 8
-and lower comes to mind). The main problem is that the configure script
-detect the contextes 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 ;)
+and lower or old alpha linuxes comes to mind). The main problem is that the
+configure script detect the contextes 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 ;)
\subsection faq_context_10000 I want hundred thousands of simulated processes
Unfortunately, we cannot debug every code written in SimGrid. We
furthermore believe that the framework provides ways enough
information to debug such informations yourself. If the textual output
-is not enough, Make sure to check the \ref faq_paje FAQ entry to see
+is not enough, Make sure to check the \ref faq_visualization FAQ entry to see
how to get a graphical one.
Now, if you come up with a really simple example that deadlocks and
on your side... We have plenty of FAQ entries to redact and new
features to implement for the impenitents! ;)
-\author Arnaud Legrand (arnaud.legran::imag.fr)
+\author Arnaud Legrand (arnaud.legrand::imag.fr)
\author Martin Quinson (martin.quinson::loria.fr)
