* @details
* A linear maxmin solver to resolves inequations systems.
*
- * A system is composed of variables, constraints and elements linking them.
+ * Most SimGrid model rely on a "fluid/steady-state" modeling that
+ * samount to share resources between actions at relatively
+ * coarse-grain. Such sharing is generally done by solving a set of
+ * linear inequations. Let's take an example and assume we have the
+ * variables \f$x_1\f$, \f$x_2\f$, \f$x_3\f$, and \f$x_4\f$ . Let's
+ * say that \f$x_1\f$ and \f$x_2\f$ correspond to activities running
+ * and the same CPU \f$A\f$ whose capacity is \f$C_A\f$ . In such a
+ * case, we need to enforce:
+ *
+ * \f[ x_1 + x_2 \leq C_A \f]
+ *
+ * Likewise, if \f$x_3\f$ (resp. \f$x_4\f$) corresponds to a network
+ * flow \f$F_3\f$ (resp. \f$F_4\f$) that goes through a set of links
+ * \f$L_1\f$ and \f$L_2\f$ (resp. \f$L_2\f$ and \f$L_3\f$), then we
+ * need to enforce:
+ *
+ * \f[ x_3 \leq C_{L_1} \f]
+ * \f[ x_3 + x_4 \leq C_{L_2} \f]
+ * \f[ x_4 \leq C_{L_3} \f]
+ *
+ * One could set every variable to 0 to make sure the constraints are
+ * satisfied but this would obviously not be very realistic. A
+ * possible objective is to try to maximize the minimum of the
+ * \f$x_i\f$ . This ensures that all the \f$x_i\f$ are positive and "as
+ * large as possible".
+ *
+ * This is called *max-min fairness* and is the most commonly used
+ * objective in SimGrid. Another possibility is to maximize
+ * \f$\sum_if(x_i)\f$, where \f$f\f$ is a strictly increasing concave
+ * function.
+ *
* Constraint:
* - bound (set)
* - shared (set)
*/
extern double sg_maxmin_precision;
-#define MAXMIN_PRECISION sg_maxmin_precision
-static XBT_INLINE void double_update(double *variable, double value)
+extern double sg_surf_precision;
+
+static XBT_INLINE void double_update(double *variable, double value, double precision)
{
*variable -= value;
- if (*variable < MAXMIN_PRECISION)
+ if (*variable < precision)
*variable = 0.0;
}
-static XBT_INLINE int double_positive(double value)
+static XBT_INLINE int double_positive(double value, double precision)
{
- return (value > MAXMIN_PRECISION);
+ return (value > precision);
}
-static XBT_INLINE int double_equals(double value1, double value2)
+static XBT_INLINE int double_equals(double value1, double value2, double precision)
{
- return (fabs(value1 - value2) < MAXMIN_PRECISION);
+ return (fabs(value1 - value2) < precision);
}
SG_BEGIN_DECL()
*
* @param cnst The constraint to share
*/
-void lmm_constraint_shared(lmm_constraint_t cnst);
+XBT_PUBLIC(void) lmm_constraint_shared(lmm_constraint_t cnst);
/**
* @brief Check if a constraint is shared (shared by default)
* @param cnst The constraint to share
* @return 1 if shared, 0 otherwise
*/
-int lmm_constraint_is_shared(lmm_constraint_t cnst);
+XBT_PUBLIC(int) lmm_constraint_is_shared(lmm_constraint_t cnst);
/**
* @brief Free a constraint
* @param sys The system associated to the constraint
* @param cnst The constraint to free
*/
-void lmm_constraint_free(lmm_system_t sys, lmm_constraint_t cnst);
+XBT_PUBLIC(void) lmm_constraint_free(lmm_system_t sys, lmm_constraint_t cnst);
/**
* @brief Get the usage of the constraint after the last lmm solve
* @param cnst A constraint
* @return The usage of the constraint
*/
-double lmm_constraint_get_usage(lmm_constraint_t cnst);
+XBT_PUBLIC(double) lmm_constraint_get_usage(lmm_constraint_t cnst);
/**
* @brief Create a new Linear MaxMin variable
* @param var A variable
* @param value The value to add to the coefficient associated to the variable in the constraint
*/
-void lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
+XBT_PUBLIC(void) lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
lmm_variable_t var, double value);
/**
* @param num The rank of constraint we want to get
* @return The numth constraint
*/
-lmm_constraint_t lmm_get_cnst_from_var(lmm_system_t sys,
+XBT_PUBLIC(lmm_constraint_t) lmm_get_cnst_from_var(lmm_system_t sys,
lmm_variable_t var, int num);
/**
* @param num The rank of constraint we want to get
* @return The numth constraint
*/
-double lmm_get_cnst_weight_from_var(lmm_system_t sys, lmm_variable_t var,
+XBT_PUBLIC(double) lmm_get_cnst_weight_from_var(lmm_system_t sys, lmm_variable_t var,
int num);
/**
* @param var A variable
* @return The number of constraint associated to the variable
*/
-int lmm_get_number_of_cnst_from_var(lmm_system_t sys, lmm_variable_t var);
+XBT_PUBLIC(int) lmm_get_number_of_cnst_from_var(lmm_system_t sys, lmm_variable_t var);
/**
* @brief Get a var associated to a constraint
* @param elem A element of constraint of the constraint or NULL
* @return A variable associated to a constraint
*/
-lmm_variable_t lmm_get_var_from_cnst(lmm_system_t sys,
+XBT_PUBLIC(lmm_variable_t) lmm_get_var_from_cnst(lmm_system_t sys,
lmm_constraint_t cnst,
lmm_element_t * elem);
* @param sys A system
* @return The first active constraint
*/
-lmm_constraint_t lmm_get_first_active_constraint(lmm_system_t sys);
+XBT_PUBLIC(lmm_constraint_t) lmm_get_first_active_constraint(lmm_system_t sys);
/**
* @brief Get the next active constraint of a constraint in a system
*
* @return The next active constraint
*/
-lmm_constraint_t lmm_get_next_active_constraint(lmm_system_t sys,
+XBT_PUBLIC(lmm_constraint_t) lmm_get_next_active_constraint(lmm_system_t sys,
lmm_constraint_t cnst);
#ifdef HAVE_LATENCY_BOUND_TRACKING
* @param cnst A constraint
* @return The data associated to the constraint
*/
-void *lmm_constraint_id(lmm_constraint_t cnst);
+XBT_PUBLIC(void *) lmm_constraint_id(lmm_constraint_t cnst);
/**
* @brief Get the data associated to a variable
* @param var A variable
* @return The data associated to the variable
*/
-void *lmm_variable_id(lmm_variable_t var);
+XBT_PUBLIC(void *) lmm_variable_id(lmm_variable_t var);
/**
* @brief Update the value of element linking the constraint and the variable
* @param var A variable
* @param value The new value
*/
-void lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
+XBT_PUBLIC(void) lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
lmm_variable_t var, double value);
/**
* @param var A constraint
* @param bound The new bound
*/
-void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
+XBT_PUBLIC(void) lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
double bound);
/**
* @brief Update the weight of a variable
*
* @param sys A system
- * @param var A variable
+ * @param var A variable
* @param weight The new weight of the variable
*/
XBT_PUBLIC(void) lmm_update_variable_weight(lmm_system_t sys,
* @param var A variable
* @return The weight of the variable
*/
-double lmm_get_variable_weight(lmm_variable_t var);
+XBT_PUBLIC(double) lmm_get_variable_weight(lmm_variable_t var);
/**
* @brief Update a constraint bound
* @param cnst A constraint
* @return [description]
*/
-int lmm_constraint_used(lmm_system_t sys, lmm_constraint_t cnst);
+XBT_PUBLIC(int) lmm_constraint_used(lmm_system_t sys, lmm_constraint_t cnst);
/**
* @brief Solve the lmm system
