3 /* gras/emul.h - public interface to emulation support */
4 /* (specific parts for SG or RL) */
6 /* Copyright (c) 2003, 2004 Martin Quinson. All rights reserved. */
8 /* This program is free software; you can redistribute it and/or modify it
9 * under the terms of the license (GNU LGPL) which comes with this package. */
14 #include "xbt/misc.h" /* SG_BEGIN_DECL */
18 /** @addtogroup GRAS_emul
19 * @brief Code execution "emulation" and "virtualization".
21 * <center><table><tr><td><b>Top</b> <td> [\ref index]::[\ref GRAS_API]
22 * <tr><td><b>Prev</b> <td> [\ref GRAS_globals]
23 * <tr><td><b>Next</b> <td> [\ref GRAS_main_generation] </table></center>
25 * Emulation and virtualization words have a lot of different meanings in
26 * computer science. Here is what we mean, and what this module allows you
27 * to do (if it does not match your personal belives, I'm sorry):
29 * - Virtualization: Having some specific code for the simulation or for the reality
30 * - Emulation: Report within the simulator the execution time of your code
32 * \section GRAS_emul_virtualization Virtualization
34 * The whole idea of GRAS is to share the same code between the simulator
35 * and the real implementation. But it is sometimes impossible, such as
36 * when you want to deal with the OS. As an example, you may want to add
37 * some extra delay before initiating a communication in RL to ensure that
38 * the receiver is listening. This is usually useless in SG since you have
39 * a much better control on process launch time.
41 * This would be done with the following snipet:
42 * \verbatim if (gras_if_RL())
43 gras_os_sleep(1);\endverbatim
45 * Please note that those are real functions and not pre-processor
46 * defines. This is to ensure that the same object code can be linked
47 * against the SG library or the RL one without recompilation.
52 /** \brief Returns true only if the program runs on real life */
55 /** \brief Returns true only if the program runs within the simulator */
60 int gras_bench_always_begin(const char *location, int line);
61 int gras_bench_always_end(void);
62 int gras_bench_once_begin(const char *location, int line);
63 int gras_bench_once_end(void);
65 /** @addtogroup GRAS_emul
66 * \section GRAS_emul_timing Emulation
68 * For simulation accuracy, it is mandatory to report the execution time
69 * of your code into the simulator. For example, if your application is a
70 * parallel matrix multiplication, you naturally have to slow down the
71 * simulated hosts actually doing the computation.
73 * If you know beforehands how long each task will last, simply add a call
74 * to the gras_bench_fixed function described below. If not, you can have
75 * GRAS benchmarking your code automatically. Simply enclose the code to
76 * time between a macro GRAS_BENCH_*_BEGIN and GRAS_BENCH_*_END, and
77 * you're done. There is three pair of such macros, whose characteristics
78 * are summarized in the following table.
82 * <td><b>Name</b></td>
83 * <td><b>Run on host machine?</b></td>
84 * <td><b>Benchmarked?</b></td>
85 * <td><b>Corresponding time reported to simulation?</b></td>
88 * <td>GRAS_BENCH_ALWAYS_BEGIN()<br>
89 * GRAS_BENCH_ALWAYS_END()</td>
95 * <td>GRAS_BENCH_ONCE_RUN_ONCE_BEGIN()<br>
96 * GRAS_BENCH_ONCE_RUN_ONCE_END()</td>
97 * <td>Only first time</td>
98 * <td>Only first time</td>
99 * <td>Each time (with stored value)</td>
102 * <td>GRAS_BENCH_ONCE_RUN_ALWAYS_BEGIN()<br>
103 * GRAS_BENCH_ONCE_RUN_ALWAYS_END()</td>
105 * <td>Only first time</td>
106 * <td>Each time (with stored value)</td>
110 * As you can see, whatever macro pair you use, the corresponding value is
111 * repported to the simulator. After all, that's what those macro are
114 * The GRAS_BENCH_ALWAYS_* macros are the simplest ones. Each time the
115 * corresponding block is encountered, the corresponding code is executed
116 * and timed. Then, the simulated host is given the corresponding amount
119 * The GRAS_BENCH_ONCE_RUN_ONCE_* macros are good for cases where you know
120 * that your execution time is constant and where you don't care about the
121 * result in simulation mode. In our example, each sub-block
122 * multiplication takes exactly the same amount of work (time depends only
123 * on size, not on content), and the operation result can safely be
124 * ignored for algorithm result. Doing so allows you to considerably
125 * reduce the amount of computation needed when running on simulator.
127 * The GRAS_BENCH_ONCE_RUN_ALWAYS_* macros are good for cases where you
128 * know that each block will induce the same amount of work (you thus
129 * don't want to bench it each time), but you actually need the result (so
130 * you have to run it each time). You may ask why you don't use
131 * GRAS_BENCH_ONCE_RUN_ONCE_* macros in this case (why you save the
132 * benchmarking time). The timing operation is not very intrusive by
133 * itself, but it has to be done in an exclusive way between the several
134 * GRAS threads (protected by mutex). So, the day where there will be
135 * threads in GRAS, this will do a big difference. Ok, I agree. For now,
136 * it makes no difference.
140 * - Blocks are automatically differenciated using the filename and line
141 * position at which the *_BEGIN part was called. Don't put two of them
144 * - You cannot nest blocks. It would make no sense, either.
146 * - By the way, GRAS is not exactly designed for parallel algorithm such
147 * as parallel matrix multiplication but for distributed ones, you weirdo.
148 * But it's just an example ;)
152 /** \brief Start benchmarking this code block
154 #define GRAS_BENCH_ALWAYS_BEGIN() gras_bench_always_begin(__FILE__, __LINE__)
155 /** \brief Stop benchmarking this code block
157 #define GRAS_BENCH_ALWAYS_END() gras_bench_always_end()
159 /** \brief Start benchmarking this code block if it has never been benchmarked, run it in any case
160 * \hideinitializer */
161 #define GRAS_BENCH_ONCE_RUN_ALWAYS_BEGIN() gras_bench_once_begin(__FILE__, __LINE__)
162 /** \brief Stop benchmarking this part of the code
164 #define GRAS_BENCH_ONCE_RUN_ALWAYS_END() gras_bench_once_end()
166 /** \brief Start benchmarking this code block if it has never been benchmarked, ignore it if it was
168 #define GRAS_BENCH_ONCE_RUN_ONCE_BEGIN() if (gras_bench_once_begin(__FILE__, __LINE__)) {
169 /** \brief Stop benchmarking this part of the code
171 #define GRAS_BENCH_ONCE_RUN_ONCE_END() } gras_bench_once_end()
176 #endif /* GRAS_COND_H */