-/* Copyright (c) 2004-2019. The SimGrid Team. All rights reserved. */
+/* Copyright (c) 2004-2023. The SimGrid Team. All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
* under the terms of the license (GNU LGPL) which comes with this package. */
-#ifndef SURF_MAXMIN_HPP
-#define SURF_MAXMIN_HPP
+#ifndef SIMGRID_KERNEL_LMM_MAXMIN_HPP
+#define SIMGRID_KERNEL_LMM_MAXMIN_HPP
-#include "simgrid/kernel/resource/Action.hpp"
-#include "simgrid/s4u/Link.hpp"
-#include "xbt/asserts.h"
-#include "xbt/mallocator.h"
+#include "src/kernel/lmm/System.hpp"
-#include <boost/intrusive/list.hpp>
-#include <cmath>
-#include <limits>
-#include <vector>
+namespace simgrid::kernel::lmm {
-namespace simgrid {
-namespace kernel {
-namespace lmm {
-
-/** @addtogroup SURF_lmm
- * @details
- * A linear maxmin solver to resolve inequations systems.
- *
- * Most SimGrid model rely on a "fluid/steady-state" modeling that simulate the sharing of 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)
- * - usage (computed)
- *
- * Variable:
- * - weight (set)
- * - bound (set)
- * - value (computed)
- *
- * Element:
- * - value (set)
- *
- * A possible system could be:
- * - three variables: `var1`, `var2`, `var3`
- * - two constraints: `cons1`, `cons2`
- * - four elements linking:
- * - `elem1` linking `var1` and `cons1`
- * - `elem2` linking `var2` and `cons1`
- * - `elem3` linking `var2` and `cons2`
- * - `elem4` linking `var3` and `cons2`
- *
- * And the corresponding inequations will be:
- *
- * var1.value <= var1.bound
- * var2.value <= var2.bound
- * var3.value <= var3.bound
- * var1.weight * var1.value * elem1.value + var2.weight * var2.value * elem2.value <= cons1.bound
- * var2.weight * var2.value * elem3.value + var3.weight * var3.value * elem4.value <= cons2.bound
- *
- * where `var1.value`, `var2.value` and `var3.value` are the unknown values.
- *
- * If a constraint is not shared, the sum is replaced by a max.
- * For example, a third non-shared constraint `cons3` and the associated elements `elem5` and `elem6` could write as:
- *
- * max( var1.weight * var1.value * elem5.value , var3.weight * var3.value * elem6.value ) <= cons3.bound
- *
- * This is useful for the sharing of resources for various models.
- * For instance, for the network model, each link is associated to a constraint and each communication to a variable.
- *
- * Implementation details
- *
- * For implementation reasons, we are interested in distinguishing variables that actually participate to the
- * computation of constraints, and those who are part of the equations but are stuck to zero.
- * We call enabled variables, those which var.weight is strictly positive. Zero-weight variables are called disabled
- * variables.
- * Unfortunately this concept of enabled/disabled variables intersects with active/inactive variable.
- * Semantically, the intent is similar, but the conditions under which a variable is active is slightly more strict
- * than the conditions for it to be enabled.
- * A variable is active only if its var.value is non-zero (and, by construction, its var.weight is non-zero).
- * In general, variables remain disabled after their creation, which often models an initialization phase (e.g. first
- * packet propagating in the network). Then, it is enabled by the corresponding model. Afterwards, the max-min solver
- * (lmm_solve()) activates it when appropriate. It is possible that the variable is again disabled, e.g. to model the
- * pausing of an action.
- *
- * Concurrency limit and maximum
- *
- * We call concurrency, the number of variables that can be enabled at any time for each constraint.
- * From a model perspective, this "concurrency" often represents the number of actions that actually compete for one
- * constraint.
- * The LMM solver is able to limit the concurrency for each constraint, and to monitor its maximum value.
- *
- * One may want to limit the concurrency of constraints for essentially three reasons:
- * - Keep LMM system in a size that can be solved (it does not react very well with tens of thousands of variables per
- * constraint)
- * - Stay within parameters where the fluid model is accurate enough.
- * - Model serialization effects
- *
- * The concurrency limit can also be set to a negative value to disable concurrency limit. This can improve performance
- * slightly.
- *
- * Overall, each constraint contains three fields related to concurrency:
- * - concurrency_limit which is the limit enforced by the solver
- * - concurrency_current which is the current concurrency
- * - concurrency_maximum which is the observed maximum concurrency
- *
- * Variables also have one field related to concurrency: concurrency_share.
- * In effect, in some cases, one variable is involved multiple times (i.e. two elements) in a constraint.
- * For example, cross-traffic is modeled using 2 elements per constraint.
- * concurrency_share formally corresponds to the maximum number of elements that associate the variable and any given
- * constraint.
- */
-
-/** @{ @ingroup SURF_lmm */
-
-/**
- * @brief LMM element
- * Elements can be seen as glue between constraint objects and variable objects.
- * Basically, each variable will have a set of elements, one for each constraint where it is involved.
- * Then, it is used to list all variables involved in constraint through constraint's xxx_element_set lists, or
- * vice-versa list all constraints for a given variable.
- */
-class XBT_PUBLIC Element {
+class XBT_PUBLIC MaxMin : public System {
public:
- int get_concurrency() const;
- void decrease_concurrency();
- void increase_concurrency();
-
- void make_active();
- void make_inactive();
-
- /* hookup to constraint */
- boost::intrusive::list_member_hook<> enabled_element_set_hook;
- boost::intrusive::list_member_hook<> disabled_element_set_hook;
- boost::intrusive::list_member_hook<> active_element_set_hook;
-
- Constraint* constraint;
- Variable* variable;
-
- // consumption_weight: impact of 1 byte or flop of your application onto the resource (in byte or flop)
- // - if CPU, then probably 1.
- // - If network, then 1 in forward direction and 0.05 backward for the ACKs
- double consumption_weight;
-};
-
-class ConstraintLight {
-public:
- double remaining_over_usage;
- Constraint* cnst;
-};
-
-/**
- * @brief LMM constraint
- * Each constraint contains several partially overlapping logical sets of elements:
- * \li Disabled elements which variable's weight is zero. This variables are not at all processed by LMM, but eventually
- * the corresponding action will enable it (at least this is the idea).
- * \li Enabled elements which variable's weight is non-zero. They are utilized in some LMM functions.
- * \li Active elements which variable's weight is non-zero (i.e. it is enabled) AND its element value is non-zero.
- * LMM_solve iterates over active elements during resolution, dynamically making them active or inactive.
- */
-class XBT_PUBLIC Constraint {
-public:
- Constraint() = delete;
- Constraint(resource::Resource* id_value, double bound_value);
-
- /** @brief Unshare a constraint. */
- void unshare() { sharing_policy_ = s4u::Link::SharingPolicy::FATPIPE; }
-
- /** @brief Check how a constraint is shared */
- s4u::Link::SharingPolicy get_sharing_policy() const { return sharing_policy_; }
-
- /** @brief Get the usage of the constraint after the last lmm solve */
- double get_usage() const;
- int get_variable_amount() const;
-
- /** @brief Sets the concurrency limit for this constraint */
- void set_concurrency_limit(int limit)
- {
- xbt_assert(limit < 0 || concurrency_maximum_ <= limit,
- "New concurrency limit should be larger than observed concurrency maximum. Maybe you want to call"
- " concurrency_maximum_reset() to reset the maximum?");
- concurrency_limit_ = limit;
- }
-
- /** @brief Gets the concurrency limit for this constraint */
- int get_concurrency_limit() const { return concurrency_limit_; }
-
- /**
- * @brief Reset the concurrency maximum for a given variable (we will update the maximum to reflect constraint
- * evolution).
- */
- void reset_concurrency_maximum() { concurrency_maximum_ = 0; }
-
- /** @brief Get the concurrency maximum for a given constraint (which reflects constraint evolution). */
- int get_concurrency_maximum() const
- {
- xbt_assert(concurrency_limit_ < 0 || concurrency_maximum_ <= concurrency_limit_,
- "Very bad: maximum observed concurrency is higher than limit. This is a bug of SURF, please report it.");
- return concurrency_maximum_;
- }
-
- int get_concurrency_slack() const
- {
- return concurrency_limit_ < 0 ? std::numeric_limits<int>::max() : concurrency_limit_ - concurrency_current_;
- }
-
- /**
- * @brief Get a var associated to a constraint
- * @details Get the first variable of the next variable of elem if elem is not NULL
- * @param elem A element of constraint of the constraint or NULL
- * @return A variable associated to a constraint
- */
- Variable* get_variable(const Element** elem) const;
-
- /**
- * @brief Get a var associated to a constraint
- * @details Get the first variable of the next variable of elem if elem is not NULL
- * @param elem A element of constraint of the constraint or NULL
- * @param nextelem A element of constraint of the constraint or NULL, the one after elem
- * @param numelem parameter representing the number of elements to go
- * @return A variable associated to a constraint
- */
- Variable* get_variable_safe(const Element** elem, const Element** nextelem, int* numelem) const;
-
- /**
- * @brief Get the data associated to a constraint
- * @return The data associated to the constraint
- */
- resource::Resource* get_id() const { return id_; }
-
- /* hookup to system */
- boost::intrusive::list_member_hook<> constraint_set_hook_;
- boost::intrusive::list_member_hook<> active_constraint_set_hook_;
- boost::intrusive::list_member_hook<> modified_constraint_set_hook_;
- boost::intrusive::list_member_hook<> saturated_constraint_set_hook_;
- boost::intrusive::list<Element, boost::intrusive::member_hook<Element, boost::intrusive::list_member_hook<>,
- &Element::enabled_element_set_hook>>
- enabled_element_set_;
- boost::intrusive::list<Element, boost::intrusive::member_hook<Element, boost::intrusive::list_member_hook<>,
- &Element::disabled_element_set_hook>>
- disabled_element_set_;
- boost::intrusive::list<Element, boost::intrusive::member_hook<Element, boost::intrusive::list_member_hook<>,
- &Element::active_element_set_hook>>
- active_element_set_;
- double remaining_;
- double usage_;
- double bound_;
- // TODO MARTIN Check maximum value across resources at the end of simulation and give a warning is more than e.g. 500
- int concurrency_current_; /* The current concurrency */
- int concurrency_maximum_; /* The maximum number of (enabled and disabled) variables associated to the constraint at
- * any given time (essentially for tracing)*/
-
- s4u::Link::SharingPolicy sharing_policy_;
- int rank_; // Only used in debug messages to identify the constraint
- double lambda_;
- double new_lambda_;
- ConstraintLight* cnst_light_;
+ using System::System;
private:
- static int next_rank_; // To give a separate rank_ to each constraint
- int concurrency_limit_; /* The maximum number of variables that may be enabled at any time (stage variables if
- * necessary) */
- resource::Resource* id_;
-};
-
-/**
- * @brief LMM variable
- *
- * When something prevents us from enabling a variable, we "stage" the weight that we would have like to set, so that as
- * soon as possible we enable the variable with desired weight
- */
-class XBT_PUBLIC Variable {
-public:
- void initialize(resource::Action* id_value, double sharing_penalty, double bound_value, int number_of_constraints,
- unsigned visited_value);
-
- /** @brief Get the value of the variable after the last lmm solve */
- double get_value() const { return value_; }
-
- /** @brief Get the maximum value of the variable (-1.0 if no specified maximum) */
- double get_bound() const { return bound_; }
-
- /**
- * @brief Set the concurrent share of the variable
- * @param value The new concurrency share
- */
- void set_concurrency_share(short int value) { concurrency_share_ = value; }
-
- /**
- * @brief Get the numth constraint associated to the variable
- * @param num The rank of constraint we want to get
- * @return The numth constraint
- */
- Constraint* get_constraint(unsigned num) const { return num < cnsts_.size() ? cnsts_[num].constraint : nullptr; }
-
- /**
- * @brief Get the weigth of the numth constraint associated to the variable
- * @param num The rank of constraint we want to get
- * @return The numth constraint
- */
- double get_constraint_weight(unsigned num) const
- {
- return num < cnsts_.size() ? cnsts_[num].consumption_weight : 0.0;
- }
-
- /** @brief Get the number of constraint associated to a variable */
- size_t get_number_of_constraint() const { return cnsts_.size(); }
-
- /** @brief Get the data associated to a variable */
- resource::Action* get_id() const { return id_; }
-
- /** @brief Get the penalty of a variable */
- double get_penalty() const { return sharing_penalty_; }
-
- /** @brief Measure the minimum concurrency slack across all constraints where the given var is involved */
- int get_min_concurrency_slack() const;
-
- /** @brief Check if a variable can be enabled
- * Make sure to set staged_penalty before, if your intent is only to check concurrency
- */
- int can_enable() const { return staged_penalty_ > 0 && get_min_concurrency_slack() >= concurrency_share_; }
-
- /* hookup to system */
- boost::intrusive::list_member_hook<> variable_set_hook_;
- boost::intrusive::list_member_hook<> saturated_variable_set_hook_;
-
- std::vector<Element> cnsts_;
+ void do_solve() final;
+ template <class CnstList> void maxmin_solve(CnstList& cnst_list);
- // sharing_penalty: variable's impact on the resource during the sharing
- // if == 0, the variable is not considered by LMM
- // on CPU, actions with N threads have a sharing of N
- // on network, the actions with higher latency have a lesser sharing_penalty
- double sharing_penalty_;
+ using dyn_light_t = std::vector<int>;
- double staged_penalty_; /* If non-zero, variable is staged for addition as soon as maxconcurrency constraints will be
- met */
- double bound_;
- double value_;
- short int concurrency_share_; /* The maximum number of elements that variable will add to a constraint */
- resource::Action* id_;
- int rank_; // Only used in debug messages to identify the variable
- unsigned visited_; /* used by System::update_modified_set() */
- double mu_;
-
-private:
- static int next_rank_; // To give a separate rank_ to each variable
-};
-
-inline void Element::make_active()
-{
- constraint->active_element_set_.push_front(*this);
-}
-inline void Element::make_inactive()
-{
- if (active_element_set_hook.is_linked())
- simgrid::xbt::intrusive_erase(constraint->active_element_set_, *this);
-}
-
-/**
- * @brief LMM system
- */
-class XBT_PUBLIC System {
-public:
- /**
- * @brief Create a new Linear MaxMim system
- * @param selective_update whether we should do lazy updates
- */
- explicit System(bool selective_update);
- /** @brief Free an existing Linear MaxMin system */
- virtual ~System();
-
- /**
- * @brief Create a new Linear MaxMin constraint
- * @param id Data associated to the constraint (e.g.: a network link)
- * @param bound_value The bound value of the constraint
- */
- Constraint* constraint_new(resource::Resource* id, double bound_value);
-
- /**
- * @brief Create a new Linear MaxMin variable
- * @param id Data associated to the variable (e.g.: a network communication)
- * @param sharing_penalty The weight of the variable (0.0 if not used)
- * @param bound The maximum value of the variable (-1.0 if no maximum value)
- * @param number_of_constraints The maximum number of constraints to associate to the variable
- */
- Variable* variable_new(resource::Action* id, double sharing_penalty, double bound = -1.0,
- size_t number_of_constraints = 1);
-
- /**
- * @brief Free a variable
- * @param var The variable to free
- */
- void variable_free(Variable * var);
-
- /** @brief Free all variables */
- void variable_free_all();
-
- /**
- * @brief Associate a variable to a constraint with a coefficient
- * @param cnst A constraint
- * @param var A variable
- * @param value The coefficient associated to the variable in the constraint
- */
- void expand(Constraint * cnst, Variable * var, double value);
-
- /**
- * @brief Add value to the coefficient between a constraint and a variable or create one
- * @param cnst A constraint
- * @param var A variable
- * @param value The value to add to the coefficient associated to the variable in the constraint
- */
- void expand_add(Constraint * cnst, Variable * var, double value);
-
- /** @brief Update the bound of a variable */
- void update_variable_bound(Variable * var, double bound);
-
- /** @brief Update the sharing penalty of a variable */
- void update_variable_penalty(Variable* var, double penalty);
-
- /** @brief Update a constraint bound */
- void update_constraint_bound(Constraint * cnst, double bound);
-
- int constraint_used(Constraint* cnst) { return cnst->active_constraint_set_hook_.is_linked(); }
-
- /** @brief Print the lmm system */
- void print() const;
-
- /** @brief Solve the lmm system */
- void lmm_solve();
-
- /** @brief Solve the lmm system. May be specialized in subclasses. */
- virtual void solve() { lmm_solve(); }
-
-private:
- static void* variable_mallocator_new_f();
- static void variable_mallocator_free_f(void* var);
-
- void var_free(Variable * var);
- void cnst_free(Constraint * cnst);
- Variable* extract_variable()
- {
- if (variable_set.empty())
- return nullptr;
- Variable* res = &variable_set.front();
- variable_set.pop_front();
- return res;
- }
- Constraint* extract_constraint()
- {
- if (constraint_set.empty())
- return nullptr;
- Constraint* res = &constraint_set.front();
- constraint_set.pop_front();
- return res;
- }
- void insert_constraint(Constraint * cnst) { constraint_set.push_back(*cnst); }
- void remove_variable(Variable * var)
- {
- if (var->variable_set_hook_.is_linked())
- simgrid::xbt::intrusive_erase(variable_set, *var);
- if (var->saturated_variable_set_hook_.is_linked())
- simgrid::xbt::intrusive_erase(saturated_variable_set, *var);
- }
- void make_constraint_active(Constraint * cnst)
- {
- if (not cnst->active_constraint_set_hook_.is_linked())
- active_constraint_set.push_back(*cnst);
- }
- void make_constraint_inactive(Constraint * cnst)
- {
- if (cnst->active_constraint_set_hook_.is_linked())
- simgrid::xbt::intrusive_erase(active_constraint_set, *cnst);
- if (cnst->modified_constraint_set_hook_.is_linked())
- simgrid::xbt::intrusive_erase(modified_constraint_set, *cnst);
- }
-
- void enable_var(Variable * var);
- void disable_var(Variable * var);
- void on_disabled_var(Constraint * cnstr);
-
- /**
- * @brief Update the value of element linking the constraint and the variable
- * @param cnst A constraint
- * @param var A variable
- * @param value The new value
- */
- void update(Constraint * cnst, Variable * var, double value);
-
- void update_modified_set(Constraint * cnst);
- void update_modified_set_rec(Constraint * cnst);
-
- /** @brief Remove all constraints of the modified_constraint_set. */
- void remove_all_modified_set();
- void check_concurrency() const;
-
- template <class CnstList> void lmm_solve(CnstList& cnst_list);
-
-public:
- bool modified_ = false;
- boost::intrusive::list<Variable, boost::intrusive::member_hook<Variable, boost::intrusive::list_member_hook<>,
- &Variable::variable_set_hook_>>
- variable_set;
- boost::intrusive::list<Constraint, boost::intrusive::member_hook<Constraint, boost::intrusive::list_member_hook<>,
- &Constraint::active_constraint_set_hook_>>
- active_constraint_set;
- boost::intrusive::list<Variable, boost::intrusive::member_hook<Variable, boost::intrusive::list_member_hook<>,
- &Variable::saturated_variable_set_hook_>>
- saturated_variable_set;
- boost::intrusive::list<Constraint, boost::intrusive::member_hook<Constraint, boost::intrusive::list_member_hook<>,
- &Constraint::saturated_constraint_set_hook_>>
- saturated_constraint_set;
-
- resource::Action::ModifiedSet* modified_set_ = nullptr;
-
-private:
-
- typedef std::vector<int> dyn_light_t;
-
- //Data used in lmm::solve
std::vector<ConstraintLight> cnst_light_vec;
dyn_light_t saturated_constraints;
-
- bool selective_update_active; /* flag to update partially the system only selecting changed portions */
- unsigned visited_counter_ = 1; /* used by System::update_modified_set() and System::remove_all_modified_set() to
- * cleverly (un-)flag the constraints (more details in these functions) */
- boost::intrusive::list<Constraint, boost::intrusive::member_hook<Constraint, boost::intrusive::list_member_hook<>,
- &Constraint::constraint_set_hook_>>
- constraint_set;
- boost::intrusive::list<Constraint, boost::intrusive::member_hook<Constraint, boost::intrusive::list_member_hook<>,
- &Constraint::modified_constraint_set_hook_>>
- modified_constraint_set;
- xbt_mallocator_t variable_mallocator_ =
- xbt_mallocator_new(65536, System::variable_mallocator_new_f, System::variable_mallocator_free_f, nullptr);
-};
-
-class XBT_PUBLIC FairBottleneck : public System {
-public:
- explicit FairBottleneck(bool selective_update) : System(selective_update) {}
- void solve() final { bottleneck_solve(); }
-
-private:
- void bottleneck_solve();
};
-XBT_PUBLIC System* make_new_maxmin_system(bool selective_update);
-XBT_PUBLIC System* make_new_fair_bottleneck_system(bool selective_update);
-
-/** @} */
-}
-}
-}
+} // namespace simgrid::kernel::lmm
#endif
