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 "xbt/asserts.h"
13 #include "surf/datatypes.h"
18 /** @addtogroup SURF_lmm
20 * A linear maxmin solver to resolves inequations systems.
22 * Most SimGrid model rely on a "fluid/steady-state" modeling that
23 * samount to share resources between actions at relatively
24 * coarse-grain. Such sharing is generally done by solving a set of
25 * linear inequations. Let's take an example and assume we have the
26 * variables \f$x_1\f$, \f$x_2\f$, \f$x_3\f$, and \f$x_4\f$ . Let's
27 * say that \f$x_1\f$ and \f$x_2\f$ correspond to activities running
28 * and the same CPU \f$A\f$ whose capacity is \f$C_A\f$ . In such a
29 * case, we need to enforce:
31 * \f[ x_1 + x_2 \leq C_A \f]
33 * Likewise, if \f$x_3\f$ (resp. \f$x_4\f$) corresponds to a network
34 * flow \f$F_3\f$ (resp. \f$F_4\f$) that goes through a set of links
35 * \f$L_1\f$ and \f$L_2\f$ (resp. \f$L_2\f$ and \f$L_3\f$), then we
38 * \f[ x_3 \leq C_{L_1} \f]
39 * \f[ x_3 + x_4 \leq C_{L_2} \f]
40 * \f[ x_4 \leq C_{L_3} \f]
42 * One could set every variable to 0 to make sure the constraints are
43 * satisfied but this would obviously not be very realistic. A
44 * possible objective is to try to maximize the minimum of the
45 * \f$x_i\f$ . This ensures that all the \f$x_i\f$ are positive and "as
48 * This is called *max-min fairness* and is the most commonly used
49 * objective in SimGrid. Another possibility is to maximize
50 * \f$\sum_if(x_i)\f$, where \f$f\f$ is a strictly increasing concave
64 * A possible system could be:
65 * - three variables: `var1`, `var2`, `var3`
66 * - two constraints: `cons1`, `cons2`
67 * - four elements linking:
68 * - `elem1` linking `var1` and `cons1`
69 * - `elem2` linking `var2` and `cons1`
70 * - `elem3` linking `var2` and `cons2`
71 * - `elem4` linking `var3` and `cons2`
73 * And the corresponding inequations will be:
75 * var1.value <= var1.bound
76 * var2.value <= var2.bound
77 * var3.value <= var3.bound
78 * var1.weight * var1.value * elem1.value + var2.weight * var2.value * elem2.value <= cons1.bound
79 * var2.weight * var2.value * elem3.value + var3.weight * var3.value * elem4.value <= cons2.bound
81 * where `var1.value`, `var2.value` and `var3.value` are the unknown values
83 * if a constraint is not shared the sum is replace by a max
85 * Its usefull for the sharing of resources for various models.
86 * For instance for the network model the link are associated
87 * to consrtaint and the communications to variables.
90 extern double sg_maxmin_precision;
91 extern double sg_surf_precision;
93 static XBT_INLINE void double_update(double *variable, double value, double precision)
95 //printf("Updating %g -= %g +- %g\n",*variable,value,precision);
96 //xbt_assert(value==0 || value>precision);
97 //Check that precision is higher than the machine-dependent size of the mantissa. If not, brutal rounding may happen, and the precision mechanism is not active...
98 //xbt_assert(*variable< (2<<DBL_MANT_DIG)*precision && FLT_RADIX==2);
100 if (*variable < precision)
104 static XBT_INLINE int double_positive(double value, double precision)
106 return (value > precision);
109 static XBT_INLINE int double_equals(double value1, double value2, double precision)
111 return (fabs(value1 - value2) < precision);
116 /** @{ @ingroup SURF_lmm */
118 * @brief Create a new Linear MaxMim system
120 * @param selective_update [description]
122 XBT_PUBLIC(lmm_system_t) lmm_system_new(int selective_update);
125 * @brief Free an existing Linear MaxMin system
127 * @param sys The lmm system to free
129 XBT_PUBLIC(void) lmm_system_free(lmm_system_t sys);
132 * @brief Create a new Linear MaxMin constraint
134 * @param sys The system in which we add a constraint
135 * @param id Data associated to the constraint (e.g.: a network link)
136 * @param bound_value The bound value of the constraint
138 XBT_PUBLIC(lmm_constraint_t) lmm_constraint_new(lmm_system_t sys, void *id,
142 * @brief Share a constraint
143 * @details [long description]
145 * @param cnst The constraint to share
147 XBT_PUBLIC(void) lmm_constraint_shared(lmm_constraint_t cnst);
150 * @brief Check if a constraint is shared (shared by default)
152 * @param cnst The constraint to share
153 * @return 1 if shared, 0 otherwise
155 XBT_PUBLIC(int) lmm_constraint_is_shared(lmm_constraint_t cnst);
158 * @brief Free a constraint
160 * @param sys The system associated to the constraint
161 * @param cnst The constraint to free
163 XBT_PUBLIC(void) lmm_constraint_free(lmm_system_t sys, lmm_constraint_t cnst);
166 * @brief Get the usage of the constraint after the last lmm solve
168 * @param cnst A constraint
169 * @return The usage of the constraint
171 XBT_PUBLIC(double) lmm_constraint_get_usage(lmm_constraint_t cnst);
174 * @brief Create a new Linear MaxMin variable
176 * @param sys The system in which we add a constaint
177 * @param id Data associated to the variable (e.g.: a network communication)
178 * @param weight_value The weight of the variable (0.0 if not used)
179 * @param bound The maximum value of the variable (-1.0 if no maximum value)
180 * @param number_of_constraints The maximum number of constraint to associate to the variable
182 XBT_PUBLIC(lmm_variable_t) lmm_variable_new(lmm_system_t sys, void *id,
185 int number_of_constraints);
187 * @brief Free a variable
189 * @param sys The system associated to the variable
190 * @param var The variable to free
192 XBT_PUBLIC(void) lmm_variable_free(lmm_system_t sys, lmm_variable_t var);
195 * @brief Get the value of the variable after the last lmm solve
197 * @param var A variable
198 * @return The value of the variable
200 XBT_PUBLIC(double) lmm_variable_getvalue(lmm_variable_t var);
203 * @brief Get the maximum value of the variable (-1.0 if no maximum value)
205 * @param var A variable
206 * @return The bound of the variable
208 XBT_PUBLIC(double) lmm_variable_getbound(lmm_variable_t var);
211 * @brief Remove a variable from a constraint
213 * @param sys A system
214 * @param cnst A constraint
215 * @param var The variable to remove
217 XBT_PUBLIC(void) lmm_shrink(lmm_system_t sys, lmm_constraint_t cnst,
221 * @brief Associate a variable to a constraint with a coefficient
223 * @param sys A system
224 * @param cnst A constraint
225 * @param var A variable
226 * @param value The coefficient associated to the variable in the constraint
228 XBT_PUBLIC(void) lmm_expand(lmm_system_t sys, lmm_constraint_t cnst,
229 lmm_variable_t var, double value);
232 * @brief Add value to the coefficient between a constraint and a variable or
235 * @param sys A system
236 * @param cnst A constraint
237 * @param var A variable
238 * @param value The value to add to the coefficient associated to the variable in the constraint
240 XBT_PUBLIC(void) lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
241 lmm_variable_t var, double value);
244 * @brief Get the numth constraint associated to the variable
246 * @param sys The system associated to the variable (not used)
247 * @param var A variable
248 * @param num The rank of constraint we want to get
249 * @return The numth constraint
251 XBT_PUBLIC(lmm_constraint_t) lmm_get_cnst_from_var(lmm_system_t sys,
252 lmm_variable_t var, int num);
255 * @brief Get the weigth of the numth constraint associated to the variable
257 * @param sys The system associated to the variable (not used)
258 * @param var A variable
259 * @param num The rank of constraint we want to get
260 * @return The numth constraint
262 XBT_PUBLIC(double) lmm_get_cnst_weight_from_var(lmm_system_t sys, lmm_variable_t var,
266 * @brief Get the number of constraint associated to a variable
268 * @param sys The system associated to the variable (not used)
269 * @param var A variable
270 * @return The number of constraint associated to the variable
272 XBT_PUBLIC(int) lmm_get_number_of_cnst_from_var(lmm_system_t sys, lmm_variable_t var);
275 * @brief Get a var associated to a constraint
276 * @details Get the first variable of the next variable of elem if elem is not NULL
278 * @param sys The system associated to the variable (not used)
279 * @param cnst A constraint
280 * @param elem A element of constraint of the constraint or NULL
281 * @return A variable associated to a constraint
283 XBT_PUBLIC(lmm_variable_t) lmm_get_var_from_cnst(lmm_system_t sys,
284 lmm_constraint_t cnst,
285 lmm_element_t * elem);
288 * @brief Get a var associated to a constraint
289 * @details Get the first variable of the next variable of elem if elem is not NULL
291 * @param cnst A constraint
292 * @param elem A element of constraint of the constraint or NULL
293 * @param nextelem A element of constraint of the constraint or NULL, the one after elem
294 * @param numelem parameter representing the number of elements to go
296 * @return A variable associated to a constraint
298 XBT_PUBLIC(lmm_variable_t) lmm_get_var_from_cnst_safe(lmm_system_t /*sys*/,
299 lmm_constraint_t cnst,
300 lmm_element_t * elem,
301 lmm_element_t * nextelem,
305 * @brief Get the first active constraint of a system
307 * @param sys A system
308 * @return The first active constraint
310 XBT_PUBLIC(lmm_constraint_t) lmm_get_first_active_constraint(lmm_system_t sys);
313 * @brief Get the next active constraint of a constraint in a system
315 * @param sys A system
316 * @param cnst An active constraint of the system
318 * @return The next active constraint
320 XBT_PUBLIC(lmm_constraint_t) lmm_get_next_active_constraint(lmm_system_t sys,
321 lmm_constraint_t cnst);
323 #ifdef HAVE_LATENCY_BOUND_TRACKING
324 XBT_PUBLIC(int) lmm_is_variable_limited_by_latency(lmm_variable_t var);
328 * @brief Get the data associated to a constraint
330 * @param cnst A constraint
331 * @return The data associated to the constraint
333 XBT_PUBLIC(void *) lmm_constraint_id(lmm_constraint_t cnst);
336 * @brief Get the data associated to a variable
338 * @param var A variable
339 * @return The data associated to the variable
341 XBT_PUBLIC(void *) lmm_variable_id(lmm_variable_t var);
344 * @brief Update the value of element linking the constraint and the variable
346 * @param sys A system
347 * @param cnst A constraint
348 * @param var A variable
349 * @param value The new value
351 XBT_PUBLIC(void) lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
352 lmm_variable_t var, double value);
355 * @brief Update the bound of a variable
357 * @param sys A system
358 * @param var A constraint
359 * @param bound The new bound
361 XBT_PUBLIC(void) lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
365 * @brief Update the weight of a variable
367 * @param sys A system
368 * @param var A variable
369 * @param weight The new weight of the variable
371 XBT_PUBLIC(void) lmm_update_variable_weight(lmm_system_t sys,
376 * @brief Get the weight of a variable
378 * @param var A variable
379 * @return The weight of the variable
381 XBT_PUBLIC(double) lmm_get_variable_weight(lmm_variable_t var);
384 * @brief Update a constraint bound
386 * @param sys A system
387 * @param cnst A constraint
388 * @param bound The new bound of the consrtaint
390 XBT_PUBLIC(void) lmm_update_constraint_bound(lmm_system_t sys,
391 lmm_constraint_t cnst,
395 * @brief [brief description]
397 * @param sys A system
398 * @param cnst A constraint
399 * @return [description]
401 XBT_PUBLIC(int) lmm_constraint_used(lmm_system_t sys, lmm_constraint_t cnst);
404 * @brief Solve the lmm system
406 * @param sys The lmm system to solve
408 XBT_PUBLIC(void) lmm_solve(lmm_system_t sys);
410 XBT_PUBLIC(void) lagrange_solve(lmm_system_t sys);
411 XBT_PUBLIC(void) bottleneck_solve(lmm_system_t sys);
414 * Default functions associated to the chosen protocol. When
415 * using the lagrangian approach.
418 XBT_PUBLIC(void) lmm_set_default_protocol_function(double (*func_f)
428 XBT_PUBLIC(double func_reno_f) (lmm_variable_t var, double x);
429 XBT_PUBLIC(double func_reno_fp) (lmm_variable_t var, double x);
430 XBT_PUBLIC(double func_reno_fpi) (lmm_variable_t var, double x);
432 XBT_PUBLIC(double func_reno2_f) (lmm_variable_t var, double x);
433 XBT_PUBLIC(double func_reno2_fp) (lmm_variable_t var, double x);
434 XBT_PUBLIC(double func_reno2_fpi) (lmm_variable_t var, double x);
436 XBT_PUBLIC(double func_vegas_f) (lmm_variable_t var, double x);
437 XBT_PUBLIC(double func_vegas_fp) (lmm_variable_t var, double x);
438 XBT_PUBLIC(double func_vegas_fpi) (lmm_variable_t var, double x);
443 #endif /* _SURF_MAXMIN_H */