1 #####################################################################
2 ########################### CORE ###################################
3 #####################################################################
5 /** \addtogroup GRAS_API
7 \section GRAS_funct Offered functionnalities
8 - <b>\ref GRAS_comm</b>: Exchanging messages between peers
9 - \ref GRAS_dd : any data which may transit on the network must be
10 described beforehand so that GRAS can handle the platform
11 heterogeneity and convert them if needed.
12 - \ref GRAS_sock : this is how to open a communication channel to
13 other processes, and retrive information about them.
14 - \ref GRAS_msg : communications are message oriented. You have to
15 describe all possible messages and their payload beforehand, and
16 can then attach callbacks to the arrival of a given kind of message.
17 - \ref GRAS_timer : this is how to program repetitive and delayed
18 tasks, not unlike cron(8) and at(1). This cannot be used to timeout
19 a function (like setitimer(2) or signal(2) games could do).
20 - <b>\ref GRAS_run</b>: Running both on top of the simulator and on
21 top of real platforms, and portability support.
22 - \ref GRAS_virtu : You naturally don't want to call the
23 gettimeofday(2) function in simulation mode since it would give
24 you the time on the host running the simulation, not the time in
25 the simulated world (you are belonging to).\n
26 This a system call virtualization layer, which also acts as a
28 - \ref GRAS_globals : The use of globals is forbidden since the
29 "processes" are threads in simulation mode. \n
30 This is how to let GRAS handle your globals properly.
31 - \ref GRAS_emul : Support to emulate code excution (ie, reporting
32 execution time into the simulator and having code sections specific
33 to simulation or to real mode).
34 - <b>\ref GRAS_code</b>: Here are some tools which may help
35 you setting up a GRAS project.\n
36 Setting up and building a GRAS application is complicated by the
37 library schizoid. The code to setup the environment differs
38 depending on whether you run on the simulator on a real platform.
39 And then, you'll have to deal with the usual distributed
40 application development difficulties.
41 - \ref GRAS_main_generation : Since processes are threads in
42 simulation mode and regular processes in the real world, GRAS does
43 generate your main functions for you.
47 \section GRAS_example Examples
49 There is for now rather few examples of GRAS, but it's better than
58 /** @defgroup GRAS_comm Communication facilities */
59 /** @defgroup GRAS_run Virtualization */
60 /** @defgroup GRAS_code Project and code management */
61 /** @defgroup GRAS_ex Examples */
63 #####################################################################
64 /** @addtogroup GRAS_comm
66 Here are the communication facilities. GRAS allows you to exchange
67 <i>messages</i> on <i>sockets</i> (which can be seen as pipes between
68 processes). On reception, messages start <i>callbacks</i> (that's the
69 default communication mode, not the only one). All messages of a given
70 type convey the same kind of data, and you have to describe it
73 Timers are also seen as a mean of communication (with yourself). It
74 allows you to run a repetitive task ("do this every N second until I tell
75 you to stop"), or to deffer a treatment ("do this in 3 sec").
78 /** @defgroup GRAS_dd Data description */
79 /** @defgroup GRAS_sock Sockets */
80 /** @defgroup GRAS_msg Messages */
81 /** @defgroup GRAS_timer Timers */
84 #####################################################################
85 /** @addtogroup GRAS_run
87 Virtualization facilities allow your code to run both on top of the simulator or in real setting.
91 /** @defgroup GRAS_globals Globals */
92 /** @defgroup GRAS_emul Emulation support */
93 /** @defgroup GRAS_virtu Syscalls */
97 #####################################################################
98 /** @addtogroup GRAS_code
100 Here is how to setup your code when you want to use GRAS. You will also
101 learn how to get the most repetitive parts of your code generated
104 (use the tabs on top of the page to navigate)
107 DOXYGEN_NAVBAR_LABEL="Project management"
108 DOXYGEN_NAVBAR_CHILD "main() and GRAS"=GRAS_main_generation.html
109 DOXYGEN_NAVBAR_CHILD "Compiling your GRAS project"=GRAS_compile.html
113 #####################################################################
114 /** @addtogroup GRAS_ex
116 There is for now rather few examples of GRAS, but it's better than
125 DOXYGEN_NAVBAR_CHILD "Ping-Pong"=GRAS_ex_ping.html
126 DOXYGEN_NAVBAR_CHILD "RPC"=GRAS_ex_mmrpc.html
127 DOXYGEN_NAVBAR_CHILD "Token Ring"=GRAS_ex_token.html
128 DOXYGEN_NAVBAR_CHILD "Timers"=GRAS_ex_timer.html
131 There is some more examples in the distribution, under the directory
132 <tt>examples/gras</tt>.
135 #####################################################################
136 ######################### EXTRA PAGES ##############################
137 #####################################################################
139 ---------------------------------------------------------------------
140 --------------------- main() generation -----------------------------
141 ---------------------------------------------------------------------
143 /** \page GRAS_main_generation main function
145 \section GRAS_maingen_toc Table of content
147 - \ref GRAS_maingen_intro
148 - \ref GRAS_maingen_script
149 - \ref GRAS_maingen_make
153 \section GRAS_maingen_intro What's the matter with main() functions in GRAS?
155 In simulation mode, all processes are run as thread of the same process
156 while they are real processes in the real life. Unfortunately, the main
157 function of a real process must be called <tt>main</tt> while this
158 function must not use this name for threads.
160 To deal with this, you should call the main function of your processes
161 with another name (usually, the process function such as client, server,
162 or such). Then GRAS can generate the wrapper functions adapted to the
163 real and simulated modes.
165 \section GRAS_maingen_script Generating the main()s automatically
167 This is done by the gras_stub_generator program, which gets installed on
168 <tt>make install</tt> (the source resides in the tools/gras/ directory).
169 Here is the calling syntax:
170 \verbatim gras_stub_generator <project_name> <deployment_file.xml>\endverbatim
172 It parses the deployment file, searching for all the kind of processes
173 you have in your project. It then generates the following C files:
174 - a <tt>_<project_name>_<process_kind>.c</tt> file for each process kind you
176 They are used to launch your project in real life. They
177 contain a main() in charge of initializing the GRAS infrastructure and
178 launching your code afterward.
179 - a <tt>_<project_name>_simulator.c</tt> file.\n
180 This file is suited to the simulation mode. It contains a main()
181 function initializing the simulator and launching your project within.
183 For this to work, the name of process described in your deployment file
184 should match the name of a function in your code, which prototype is for
185 example: \verbatim int client(int argc,char *argv[]);\endverbatim
187 Unfortunately, all this is still partially documented. I guess I ought
188 to improve this situation somehow. In the meanwhile, check the generated
189 code and maybe also the GRAS \ref GRAS_example, sorry.
191 \section GRAS_maingen_make Integration within an hand-made Makefile
193 The easiest to set it up is to add the following chunk at the end of
194 your Makefile (or Makefile.am), putting the right values into NAME and
196 \verbatim NAME=your_project_name
197 PROCESSES=list of processes type in your project
199 $(foreach proc, $(PROCESSES), _$(NAME)_$(proc).c) _$(NAME)_simulator.c: $(NAME).c $(NAME)_deployment.xml
200 path/to/gras_stub_generator $(NAME) $(NAME)_deployment.xml >/dev/null
203 Of course, your personal millage may vary. For the \ref GRAS_ex_ping, may read:
204 \verbatim _ping_client.c _ping_server.c _ping_simulator.c: ping.c ping_deployment.xml
205 $(top_srcdir)/tools/gras/gras_stub_generator ping ping_deployment.xml >/dev/null
209 Actually, gras_stub_generator also generates some makefiles both for
210 local compilation and remote code distribution and installation. See the
211 section \ref GRAS_compile for more details.
215 ---------------------------------------------------------------------
216 ------------------------- Compiling ---------------------------------
217 ---------------------------------------------------------------------
219 /** \page GRAS_compile Compiling your project
221 As explained in section \ref GRAS_main_generation, the
222 gras_stub_generator tool can be used to generate the system
223 initialization code in your projet. While we were at this, this tool
224 also generates the makefiles you will need to compile your project
227 Code source deployment and remote compilation also constitutes a
228 challenging area in distributed applications development. The GRASPE
229 (GRAS Platform Expender) tool was designed to make this less painful.
231 \section GRAS_compile_toc Table of content
233 - \ref GRAS_compile_local
234 - \ref GRAS_compile_local_install
235 - \ref GRAS_compile_local_helpfiles
236 - \ref GRAS_compile_local_makefile
237 - \ref GRAS_compile_remote
241 \section GRAS_compile_local Local compilation of GRAS projects
243 \subsection GRAS_compile_local_install Installing SimGrid and GRAS
245 To compile locally a GRAS project, you first need to install SimGrid on
246 your machine. Use the --prefix flag to the configure script to specify
247 where you want to install the toolkit (refere to section \ref
248 faq_compiling for more information)
250 \subsection GRAS_compile_local_helpfiles Simulation description files
252 Then, you will probably need to write a platform description file and
253 application deployment description file to feed the simulator with. This
254 part is unfortunatelly not documented enough. Files examples can be
255 found along with the MSG \ref MSG_ex_master_slave example.
257 \note yes, both platform and application description files are portable
258 between MSG and GRAS. Actually, there depend on the SURF, not on the
259 programming environment you use.
261 For the first try, you could probably reuse the provided platform file
262 as is while you will need to adapt the application file to fit your
265 To generate new platform files, we usually use the Tiers Topology
266 Generator (ask google about it) and annotate the generated graph with
267 home-made scripts to let them fit the SURF. Those scripts live in the
268 tools/platform_generation/ directory of the distribution.
270 \subsection GRAS_compile_local_makefile Generating a Makefile usable for your project
272 From the information contained in the application description file, the
273 gras_stub_generator tool can create a Makefile which can be used to
274 seamlessly compile your project. Just go to the directory containing all
275 your project files, and type:
277 \verbatim path/to/gras_stub_generator [project_name] [application_deployment.file] >/dev/null
280 The first argument is the name of your project, such as
281 "MyLovelyApplication" while the second one is the application deployment
284 Several files get generated by this command. One C file per kind of
285 process in your project (such as "master" and "slave") plus one C file
286 for simulating your project. All those files are (or should ;) described
287 in section \ref GRAS_main_generation.
289 The most intersting file in this context is
290 [project_name].Makefile.local (you can safely ignore the others for
291 now). To use it, simply type (from your project main directory):
293 \verbatim GRAS_ROOT=/path/to/simgrid/installation make -f [project_name].Makefile.local
296 And that's it, all the binaries are built and linked against the correct
299 \section GRAS_compile_remote Distribution and remote compilation of GRAS projects
301 Actually, there is two somehow parallel ways to do so since both Arnaud
302 and Martin gave it a try. Merging both approaches is underway. As usual,
303 if you want to help, you're welcome ;)
307 #####################################################################
308 ######################### EXAMPLES #################################
309 #####################################################################
311 ---------------------------------------------------------------------
312 ------------------------- Ping Pong ---------------------------------
313 ---------------------------------------------------------------------
315 /** \page GRAS_ex_ping The classical Ping-Pong in GRAS
317 This example implements the very classical ping-pong in GRAS. It
318 involves a client (initiating the ping-pong) and a server (answering to
321 It works the following way:
322 - Both the client and the server register all needed messages
323 - The server registers a callback to the ping message, which sends pong
325 - The client sends the ping message to the server, and waits for the
326 pong message as an answer.
328 This example resides in the <b>examples/gras/ping/ping.c</b> file. Yes, both
329 the code of the client and of the server is placed in the same file. See
330 the \ref GRAS_main_generation section if wondering.
332 \section GRAS_ex_ping_toc Table of contents of the ping example
333 - \ref GRAS_ex_ping_common
334 - \ref GRAS_ex_ping_initial
335 - \ref GRAS_ex_ping_register
336 - \ref GRAS_ex_ping_server
337 - \ref GRAS_ex_ping_serdata
338 - \ref GRAS_ex_ping_sercb
339 - \ref GRAS_ex_ping_sermain
340 - \ref GRAS_ex_ping_client
341 - \ref GRAS_ex_ping_climain
345 \dontinclude gras/ping/ping_common.c
347 \section GRAS_ex_ping_common 1) Common code to the client and the server
349 \subsection GRAS_ex_ping_initial 1.a) Initial settings
351 Let's first load the module header and declare a logging category (see
352 \ref XBT_log for more info on logging).
357 The module header <tt>ping.h</tt> reads:
359 \dontinclude gras/ping/ping.h
364 \subsection GRAS_ex_ping_register 1.b) Register the messages
366 This function, called by both the client and the server is in charge of
367 declaring the existing messages to GRAS. Since the payload does not
368 involve any newly created types but only int, this is quite easy.
369 (to exchange more complicated types, see \ref GRAS_dd or
370 \ref GRAS_ex_mmrpc for an example).
372 \dontinclude gras/ping/ping_common.c
373 \skip register_messages
376 [Back to \ref GRAS_ex_ping_toc]
378 \section GRAS_ex_ping_server 2) Server's code
380 \subsection GRAS_ex_ping_serdata 2.a) The server's globals
382 In order to ensure the communication between the "main" and the callback
383 of the server, we need to declare some globals. We have to put them in a
384 struct definition so that they can be handled properly in GRAS (see the
385 \ref GRAS_globals for more info).
387 \dontinclude gras/ping/ping_server.c
391 \subsection GRAS_ex_ping_sercb 2.b) The callback to the ping message
393 Here is the callback run when the server receives any ping message (this
394 will be registered later by the server).
396 \skip server_cb_ping_handler
397 \until end_of_server_cb_ping_handler
399 \subsection GRAS_ex_ping_sermain 2.c) The "main" of the server
401 This is the "main" of the server. As explained in the \ref
402 GRAS_main_generation, you must not write any main()
403 function yourself. Instead, you just have to write a regular function
404 like this one which will act as a main.
409 [Back to \ref GRAS_ex_ping_toc]
411 \section GRAS_ex_ping_client 3) Client's code
413 \subsection GRAS_ex_ping_climain 3.a) Client's "main" function
415 This function is quite straightforward, and the inlined comments should
416 be enough to understand it.
418 \dontinclude gras/ping/ping_client.c
422 [Back to \ref GRAS_ex_ping_toc]
425 ---------------------------------------------------------------------
426 --------------------- Simple Token Ring -----------------------------
427 ---------------------------------------------------------------------
429 /** \page GRAS_ex_token Token Ring example
431 This example implements the token ring algorithm. It involves several
432 nodes arranged in a ring (each of them have a left and a right neighbour)
433 and exchanging a "token". This algorithm is one of the solution to ensure
434 the mutual exclusion between distributed processes. There is only one
435 token at any time, so the process in its possession is ensured to be the
436 only one having it. So, if there is an action you want all processes to
437 do alternativly, but you cannot afford to have two processes doing it at
438 the same time, let the process having the token doing it.
440 Actually, there is a lot of different token ring algorithms in the
441 litterature, so this example implements one of them: the simplest one.
442 The ring is static (no new node can join it, and you'll get trouble if
443 one node dies or leaves), and nothing is done for the case in which the
446 - \ref GRAS_ex_stoken_deploy
447 - \ref GRAS_ex_stoken_global
448 - \ref GRAS_ex_stoken_callback
449 - \ref GRAS_ex_stoken_main
451 \section GRAS_ex_stoken_deploy 1) Deployment file
453 Here is the deployment file:
454 \include examples/gras/tokenS/tokenS_deployment.xml
456 The neighbour of each node is given at startup as command line argument.
457 Moreover, one of the nodes is instructed by a specific argument (the one
458 on Tremblay here) to create the token at the begining of the algorithm.
460 \section GRAS_ex_stoken_global 2) Global definition
462 The token is incarned by a specific message, which circulates from node
463 to node (the payload is an integer incremented at each hop). So, the most
464 important part of the code is the message callback, which forwards the
465 message to the next node. That is why we have to store all variable in a
466 global, as explained in the \ref GRAS_globals section.
468 \dontinclude examples/gras/tokenS/tokenS.c
472 \section GRAS_ex_stoken_callback 3) The callback
474 Even if this is the core of this algorithm, this function is quite
477 \skip node_cb_stoken_handler
478 \until end_of_node_cb_stoken_handler
480 \section GRAS_ex_stoken_main 4) The main function
482 This function is splited in two parts: The first one performs all the
483 needed initialisations (points 1-7) while the end (point 8. below) calls
484 gras_msg_handle() as long as the planned amount of ring loops are not
492 ---------------------------------------------------------------------
493 -------------------------- MM RPC -----------------------------------
494 ---------------------------------------------------------------------
496 /** \page GRAS_ex_mmrpc A simple RPC for matrix multiplication
498 This example implements a remote matrix multiplication. It involves a client
499 (creating the matrices and sending the multiplications requests) and a server
500 (computing the multiplication on client's behalf).
502 This example also constitutes a more advanced example of data description
503 mechanisms, since the message payload type is a bit more complicated than in
504 other examples such as the ping one (\ref GRAS_ex_ping).
506 It works the following way (not very different from the ping example):
507 - Both the client and the server register all needed messages and datatypes
508 - The server registers a callback to the "request" message, which computes
509 what needs to be and returns the result to the expeditor.
510 - The client creates two matrices, ask for their multiplication and check
513 This example resides in the <b>examples/gras/mmrpc/mmrpc.c</b> file. (See
514 the \ref GRAS_main_generation section if wondering why both the server
515 and the client live in the same source file)
517 \section GRAS_ex_mmrpc_toc Table of contents of the mmrpc example
518 - \ref GRAS_ex_mmrpc_common
519 - \ref GRAS_ex_mmrpc_header
520 - \ref GRAS_ex_mmrpc_dataregister
521 - \ref GRAS_ex_mmrpc_logdef
522 - \ref GRAS_ex_mmrpc_msgregister
523 - \ref GRAS_ex_mmrpc_matdump
524 - \ref GRAS_ex_mmrpc_server
525 - \ref GRAS_ex_mmrpc_serinc
526 - \ref GRAS_ex_mmrpc_sercb
527 - \ref GRAS_ex_mmrpc_sermain
528 - \ref GRAS_ex_mmrpc_client
529 - \ref GRAS_ex_mmrpc_cliinc
530 - \ref GRAS_ex_mmrpc_climain
535 \section GRAS_ex_mmrpc_common 1) Common code to the client and the server (mmrpc_common.c and mmrpc.h)
538 \subsection GRAS_ex_mmrpc_header 1.a) Module header (mmrpc.h)
540 This loads the gras header and declare the function's prototypes as well
543 \dontinclude gras/mmrpc/mmrpc.h
548 \subsection GRAS_ex_mmrpc_dataregister 1.b) Register the data types (mmrpc.h)
550 The messages involved in this example do use structures as payload,
551 so we have to declare it to GRAS. Hopefully, this can be done easily by enclosing
552 the structure declaration within a \ref GRAS_DEFINE_TYPE macro call. It will then copy this
553 declaration into an hidden string variable, which can be automatically parsed at
554 run time. Of course, the declaration is also copied unmodified by this macro, so that it
555 gets parsed by the compiler also.
557 There is some semantic that GRAS cannot guess alone and you need to <i>annotate</i>
558 your declaration to add some. For example, the ctn pointer can be a reference to an
559 object or a whole array (in which case you also has to specify its size). This is done
560 with the GRAS_ANNOTE call. It is removed from the text passed to the compiler, but it helps
561 GRAS getting some information about the semantic of your data. Here, it says that \a ctn is an
562 array, which size is the result of the operation \a rows * \a cols (with \a rows and \a cols
563 being the other fields of the structure).
565 Please note that this annotation mechanism is not as robust and cool as this example seems to
566 imply. If you want to use it yourself, you'd better use the exact right syntax, which is
567 detailed in the \ref GRAS_dd section.
569 \skip GRAS_DEFINE_TYPE
572 \subsection GRAS_ex_mmrpc_logdef 1.c) Logging category definition (mmrpc_common.c)
574 Let's first load the module header and declare a logging category (see
575 \ref XBT_log for more info on logging). This logging category does live
576 in this file (ie the required symbols are defined here and declared as
577 "extern" in any other file using them). That is why we use
578 \ref XBT_LOG_NEW_DEFAULT_CATEGORY here and
579 \ref XBT_LOG_EXTERNAL_DEFAULT_CATEGORY in mmrpc_client.c and mmrpc_server.c.
581 \dontinclude gras/mmrpc/mmrpc_common.c
585 \subsection GRAS_ex_mmrpc_msgregister 1.d) Register the messages (mmrpc_common.c)
587 This function, called by both the client and the server is in charge of
588 declaring the existing messages to GRAS. Note the use of the \ref gras_datadesc_by_symbol
589 function to parse and retrieve the structure declaration which were passed to \ref GRAS_DEFINE_TYPE
592 The datatype description builded that way can then be used to build an array datatype or
595 \skip register_messages
598 \subsection GRAS_ex_mmrpc_matdump 1.e) Helper debugging function (mmrpc_common.c)
600 This function dumps a matrix to screen for debugging.
606 [Back to \ref GRAS_ex_mmrpc_toc]
608 \section GRAS_ex_mmrpc_server 2) Server's code (mmrpc_server.c)
610 \subsection GRAS_ex_mmrpc_serinc 2.a) Server intial settings
612 All module symbols live in the mmrpc_common.c file. We thus have to
613 define \ref GRAS_DEFINE_TYPE_EXTERN to the preprocessor so that the
614 \ref GRAS_DEFINE_TYPE symbols don't get included here. Likewise, we use
615 \ref XBT_LOG_EXTERNAL_DEFAULT_CATEGORY to get the log category in here.
617 \dontinclude gras/mmrpc/mmrpc_server.c
621 \subsection GRAS_ex_mmrpc_sercb 2.b) The callback to the mmrpc message
623 Here is the callback run when the server receives any mmrpc message (this
624 will be registered later by the server). Note the way we get the message
625 payload. In the ping example, there was one additional level of pointer
626 indirection (see \ref GRAS_ex_ping_sercb). This is because the payload is
627 an array here (ie a pointer) whereas it is a scalar in the ping example.
629 \skip server_cb_request_handler
630 \until end_of_server_cb_request_handler
632 \subsection GRAS_ex_mmrpc_sermain 2.c) The "main" of the server
634 This is the "main" of the server. As explained in the \ref
635 GRAS_main_generation, you must not write any main()
636 function yourself. Instead, you just have to write a regular function
637 like this one which will act as a main.
642 [Back to \ref GRAS_ex_mmrpc_toc]
644 \section GRAS_ex_mmrpc_client 3) Client's code (mmrpc_client.c)
646 \subsection GRAS_ex_mmrpc_cliinc 2.a) Server intial settings
648 As for the server, some extra love is needed to make sure that automatic
649 datatype parsing and log categories do work even if we are using several
652 \dontinclude gras/mmrpc/mmrpc_client.c
656 \subsection GRAS_ex_mmrpc_climain 3.b) Client's "main" function
658 This function is quite straightforward, and the inlined comments should
659 be enough to understand it.
661 \dontinclude gras/mmrpc/mmrpc_client.c
665 [Back to \ref GRAS_ex_mmrpc_toc]
668 ---------------------------------------------------------------------
669 ---------------------------- Timers ---------------------------------
670 ---------------------------------------------------------------------
672 /** \page GRAS_ex_timer Some timer games
674 This example fools around with the GRAS timers (\ref GRAS_timer). It is
675 mainly a regression test, since it uses almost all timer features.
677 The main program registers a repetititive task and a delayed one, and
678 then loops until the <tt>still_to_do</tt> variables of its globals reach
679 0. The delayed task set it to 5, and the repetititive one decrease it
680 each time. Here is an example of output:
681 \verbatim Initialize GRAS
683 [1108335471] Programming the repetitive_action with a frequency of 1.000000 sec
684 [1108335471] Programming the delayed_action for after 2.000000 sec
685 [1108335471] Have a rest
686 [1108335472] Canceling the delayed_action.
687 [1108335472] Re-programming the delayed_action for after 2.000000 sec
688 [1108335472] Repetitive_action has nothing to do yet
689 [1108335473] Repetitive_action has nothing to do yet
690 [1108335473] delayed_action setting globals->still_to_do to 5
691 [1108335474] repetitive_action decrementing globals->still_to_do. New value: 4
692 [1108335475] repetitive_action decrementing globals->still_to_do. New value: 3
693 [1108335476] repetitive_action decrementing globals->still_to_do. New value: 2
694 [1108335477] repetitive_action decrementing globals->still_to_do. New value: 1
695 [1108335478] repetitive_action decrementing globals->still_to_do. New value: 0
696 Exiting GRAS\endverbatim
699 - \ref GRAS_ex_timer_decl
700 - \ref GRAS_ex_timer_delay
701 - \ref GRAS_ex_timer_repeat
702 - \ref GRAS_ex_timer_main
706 \section GRAS_ex_timer_decl 1. Declarations and headers
710 \section GRAS_ex_timer_delay 2. Source code of the delayed action
711 \skip repetitive_action
712 \until end_of_repetitive_action
714 \section GRAS_ex_timer_repeat 3. Source code of the repetitive action
716 \until end_of_delayed_action
718 \section GRAS_ex_timer_main 4. Source code of main function