1 /* Copyright (c) 2004-2014. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
12 #include "surf/datatypes.h"
16 /** @addtogroup SURF_lmm
18 * A linear maxmin solver to resolves inequations systems.
20 * Most SimGrid model rely on a "fluid/steady-state" modeling that
21 * samount to share resources between actions at relatively
22 * coarse-grain. Such sharing is generally done by solving a set of
23 * linear inequations. Let's take an example and assume we have the
24 * variables \f$x_1\f$, \f$x_2\f$, \f$x_3\f$, and \f$x_4\f$ . Let's
25 * say that \f$x_1\f$ and \f$x_2\f$ correspond to activities running
26 * and the same CPU \f$A\f$ whose capacity is \f$C_A\f$ . In such a
27 * case, we need to enforce:
29 * \f[ x_1 + x_2 \leq C_A \f]
31 * Likewise, if \f$x_3\f$ (resp. \f$x_4\f$) corresponds to a network
32 * flow \f$F_3\f$ (resp. \f$F_4\f$) that goes through a set of links
33 * \f$L_1\f$ and \f$L_2\f$ (resp. \f$L_2\f$ and \f$L_3\f$), then we
36 * \f[ x_3 \leq C_{L_1} \f]
37 * \f[ x_3 + x_4 \leq C_{L_2} \f]
38 * \f[ x_4 \leq C_{L_3} \f]
40 * One could set every variable to 0 to make sure the constraints are
41 * satisfied but this would obviously not be very realistic. A
42 * possible objective is to try to maximize the minimum of the
43 * \f$x_i\f$ . This ensures that all the \f$x_i\f$ are positive and "as
46 * This is called *max-min fairness* and is the most commonly used
47 * objective in SimGrid. Another possibility is to maximize
48 * \f$\sum_if(x_i)\f$, where \f$f\f$ is a strictly increasing concave
62 * A possible system could be:
63 * - three variables: `var1`, `var2`, `var3`
64 * - two constraints: `cons1`, `cons2`
65 * - four elements linking:
66 * - `elem1` linking `var1` and `cons1`
67 * - `elem2` linking `var2` and `cons1`
68 * - `elem3` linking `var2` and `cons2`
69 * - `elem4` linking `var3` and `cons2`
71 * And the corresponding inequations will be:
73 * var1.value <= var1.bound
74 * var2.value <= var2.bound
75 * var3.value <= var3.bound
76 * var1.weight * var1.value * elem1.value + var2.weight * var2.value * elem2.value <= cons1.bound
77 * var2.weight * var2.value * elem3.value + var3.weight * var3.value * elem4.value <= cons2.bound
79 * where `var1.value`, `var2.value` and `var3.value` are the unknown values
81 * if a constraint is not shared the sum is replace by a max
83 * Its usefull for the sharing of resources for various models.
84 * For instance for the network model the link are associated
85 * to consrtaint and the communications to variables.
88 extern double sg_maxmin_precision;
89 extern double sg_surf_precision;
91 static XBT_INLINE void double_update(double *variable, double value, double precision)
94 if (*variable < precision)
98 static XBT_INLINE int double_positive(double value, double precision)
100 return (value > precision);
103 static XBT_INLINE int double_equals(double value1, double value2, double precision)
105 return (fabs(value1 - value2) < precision);
110 /** @{ @ingroup SURF_lmm */
112 * @brief Create a new Linear MaxMim system
114 * @param selective_update [description]
116 XBT_PUBLIC(lmm_system_t) lmm_system_new(int selective_update);
119 * @brief Free an existing Linear MaxMin system
121 * @param sys The lmm system to free
123 XBT_PUBLIC(void) lmm_system_free(lmm_system_t sys);
126 * @brief Create a new Linear MaxMin constraint
128 * @param sys The system in which we add a constraint
129 * @param id Data associated to the constraint (e.g.: a network link)
130 * @param bound_value The bound value of the constraint
132 XBT_PUBLIC(lmm_constraint_t) lmm_constraint_new(lmm_system_t sys, void *id,
136 * @brief Share a constraint
137 * @details [long description]
139 * @param cnst The constraint to share
141 XBT_PUBLIC(void) lmm_constraint_shared(lmm_constraint_t cnst);
144 * @brief Check if a constraint is shared (shared by default)
146 * @param cnst The constraint to share
147 * @return 1 if shared, 0 otherwise
149 XBT_PUBLIC(int) lmm_constraint_is_shared(lmm_constraint_t cnst);
152 * @brief Free a constraint
154 * @param sys The system associated to the constraint
155 * @param cnst The constraint to free
157 XBT_PUBLIC(void) lmm_constraint_free(lmm_system_t sys, lmm_constraint_t cnst);
160 * @brief Get the usage of the constraint after the last lmm solve
162 * @param cnst A constraint
163 * @return The usage of the constraint
165 XBT_PUBLIC(double) lmm_constraint_get_usage(lmm_constraint_t cnst);
168 * @brief Create a new Linear MaxMin variable
170 * @param sys The system in which we add a constaint
171 * @param id Data associated to the variable (e.g.: a network communication)
172 * @param weight_value The weight of the variable (0.0 if not used)
173 * @param bound The maximum value of the variable (-1.0 if no maximum value)
174 * @param number_of_constraints The maximum number of constraint to associate to the variable
176 XBT_PUBLIC(lmm_variable_t) lmm_variable_new(lmm_system_t sys, void *id,
179 int number_of_constraints);
181 * @brief Free a variable
183 * @param sys The system associated to the variable
184 * @param var The variable to free
186 XBT_PUBLIC(void) lmm_variable_free(lmm_system_t sys, lmm_variable_t var);
189 * @brief Get the value of the variable after the last lmm solve
191 * @param var A variable
192 * @return The value of the variable
194 XBT_PUBLIC(double) lmm_variable_getvalue(lmm_variable_t var);
197 * @brief Get the maximum value of the variable (-1.0 if no maximum value)
199 * @param var A variable
200 * @return The bound of the variable
202 XBT_PUBLIC(double) lmm_variable_getbound(lmm_variable_t var);
205 * @brief Remove a variable from a constraint
207 * @param sys A system
208 * @param cnst A constraint
209 * @param var The variable to remove
211 XBT_PUBLIC(void) lmm_shrink(lmm_system_t sys, lmm_constraint_t cnst,
215 * @brief Associate a variable to a constraint with a coefficient
217 * @param sys A system
218 * @param cnst A constraint
219 * @param var A variable
220 * @param value The coefficient associated to the variable in the constraint
222 XBT_PUBLIC(void) lmm_expand(lmm_system_t sys, lmm_constraint_t cnst,
223 lmm_variable_t var, double value);
226 * @brief Add value to the coefficient between a constraint and a variable or
229 * @param sys A system
230 * @param cnst A constraint
231 * @param var A variable
232 * @param value The value to add to the coefficient associated to the variable in the constraint
234 XBT_PUBLIC(void) lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
235 lmm_variable_t var, double value);
238 * @brief Get the numth constraint associated to the variable
240 * @param sys The system associated to the variable (not used)
241 * @param var A variable
242 * @param num The rank of constraint we want to get
243 * @return The numth constraint
245 XBT_PUBLIC(lmm_constraint_t) lmm_get_cnst_from_var(lmm_system_t sys,
246 lmm_variable_t var, int num);
249 * @brief Get the weigth of the numth constraint associated to the variable
251 * @param sys The system associated to the variable (not used)
252 * @param var A variable
253 * @param num The rank of constraint we want to get
254 * @return The numth constraint
256 XBT_PUBLIC(double) lmm_get_cnst_weight_from_var(lmm_system_t sys, lmm_variable_t var,
260 * @brief Get the number of constraint associated to a variable
262 * @param sys The system associated to the variable (not used)
263 * @param var A variable
264 * @return The number of constraint associated to the variable
266 XBT_PUBLIC(int) lmm_get_number_of_cnst_from_var(lmm_system_t sys, lmm_variable_t var);
269 * @brief Get a var associated to a constraint
270 * @details Get the first variable of the next variable of elem if elem is not NULL
272 * @param sys The system associated to the variable (not used)
273 * @param cnst A constraint
274 * @param elem A element of constraint of the constraint or NULL
275 * @return A variable associated to a constraint
277 XBT_PUBLIC(lmm_variable_t) lmm_get_var_from_cnst(lmm_system_t sys,
278 lmm_constraint_t cnst,
279 lmm_element_t * elem);
282 * @brief Get the first active constraint of a system
284 * @param sys A system
285 * @return The first active constraint
287 XBT_PUBLIC(lmm_constraint_t) lmm_get_first_active_constraint(lmm_system_t sys);
290 * @brief Get the next active constraint of a constraint in a system
292 * @param sys A system
293 * @param cnst An active constraint of the system
295 * @return The next active constraint
297 XBT_PUBLIC(lmm_constraint_t) lmm_get_next_active_constraint(lmm_system_t sys,
298 lmm_constraint_t cnst);
300 #ifdef HAVE_LATENCY_BOUND_TRACKING
301 XBT_PUBLIC(int) lmm_is_variable_limited_by_latency(lmm_variable_t var);
305 * @brief Get the data associated to a constraint
307 * @param cnst A constraint
308 * @return The data associated to the constraint
310 XBT_PUBLIC(void *) lmm_constraint_id(lmm_constraint_t cnst);
313 * @brief Get the data associated to a variable
315 * @param var A variable
316 * @return The data associated to the variable
318 XBT_PUBLIC(void *) lmm_variable_id(lmm_variable_t var);
321 * @brief Update the value of element linking the constraint and the variable
323 * @param sys A system
324 * @param cnst A constraint
325 * @param var A variable
326 * @param value The new value
328 XBT_PUBLIC(void) lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
329 lmm_variable_t var, double value);
332 * @brief Update the bound of a variable
334 * @param sys A system
335 * @param var A constraint
336 * @param bound The new bound
338 XBT_PUBLIC(void) lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
342 * @brief Update the weight of a variable
344 * @param sys A system
345 * @param var A variable
346 * @param weight The new weight of the variable
348 XBT_PUBLIC(void) lmm_update_variable_weight(lmm_system_t sys,
353 * @brief Get the weight of a variable
355 * @param var A variable
356 * @return The weight of the variable
358 XBT_PUBLIC(double) lmm_get_variable_weight(lmm_variable_t var);
361 * @brief Update a constraint bound
363 * @param sys A system
364 * @param cnst A constraint
365 * @param bound The new bound of the consrtaint
367 XBT_PUBLIC(void) lmm_update_constraint_bound(lmm_system_t sys,
368 lmm_constraint_t cnst,
372 * @brief [brief description]
374 * @param sys A system
375 * @param cnst A constraint
376 * @return [description]
378 XBT_PUBLIC(int) lmm_constraint_used(lmm_system_t sys, lmm_constraint_t cnst);
381 * @brief Solve the lmm system
383 * @param sys The lmm system to solve
385 XBT_PUBLIC(void) lmm_solve(lmm_system_t sys);
387 XBT_PUBLIC(void) lagrange_solve(lmm_system_t sys);
388 XBT_PUBLIC(void) bottleneck_solve(lmm_system_t sys);
391 * Default functions associated to the chosen protocol. When
392 * using the lagrangian approach.
395 XBT_PUBLIC(void) lmm_set_default_protocol_function(double (*func_f)
405 XBT_PUBLIC(double func_reno_f) (lmm_variable_t var, double x);
406 XBT_PUBLIC(double func_reno_fp) (lmm_variable_t var, double x);
407 XBT_PUBLIC(double func_reno_fpi) (lmm_variable_t var, double x);
409 XBT_PUBLIC(double func_reno2_f) (lmm_variable_t var, double x);
410 XBT_PUBLIC(double func_reno2_fp) (lmm_variable_t var, double x);
411 XBT_PUBLIC(double func_reno2_fpi) (lmm_variable_t var, double x);
413 XBT_PUBLIC(double func_vegas_f) (lmm_variable_t var, double x);
414 XBT_PUBLIC(double func_vegas_fp) (lmm_variable_t var, double x);
415 XBT_PUBLIC(double func_vegas_fpi) (lmm_variable_t var, double x);
420 #endif /* _SURF_MAXMIN_H */