src/kernel/lmm/maxmin.cpp

   1 /* Copyright (c) 2004-2023. The SimGrid Team. All rights reserved.          */
   2
   3 /* This program is free software; you can redistribute it and/or modify it
   4  * under the terms of the license (GNU LGPL) which comes with this package. */
   5
   6 #include "src/kernel/lmm/maxmin.hpp"
   7 #include "src/simgrid/math_utils.h"
   8 #include "xbt/ex.h"
   9
  10 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(ker_lmm);
  11
  12 namespace simgrid::kernel::lmm {
  13
  14 using dyn_light_t = std::vector<int>;
  15
  16 static inline void saturated_constraints_update(double usage, int cnst_light_num, dyn_light_t& saturated_constraints,
  17                                                 double* min_usage)
  18 {
  19   xbt_assert(usage > 0, "Impossible");
  20
  21   if (*min_usage < 0 || *min_usage > usage) {
  22     *min_usage = usage;
  23     XBT_HERE(" min_usage=%f (cnst->remaining / cnst->usage =%f)", *min_usage, usage);
  24     saturated_constraints.assign(1, cnst_light_num);
  25   } else if (*min_usage == usage) {
  26     saturated_constraints.emplace_back(cnst_light_num);
  27   }
  28 }
  29
  30 static inline void saturated_variable_set_update(const ConstraintLight* cnst_light_tab,
  31                                                  const dyn_light_t& saturated_constraints, System* sys)
  32 {
  33   /* Add active variables (i.e. variables that need to be set) from the set of constraints to saturate
  34    * (cnst_light_tab)*/
  35   for (int const& saturated_cnst : saturated_constraints) {
  36     const ConstraintLight& cnst = cnst_light_tab[saturated_cnst];
  37     for (Element const& elem : cnst.cnst->active_element_set_) {
  38       xbt_assert(elem.variable->sharing_penalty_ > 0); // All elements of active_element_set should be active
  39       if (elem.consumption_weight > 0 && not elem.variable->saturated_variable_set_hook_.is_linked())
  40         sys->saturated_variable_set.push_back(*elem.variable);
  41     }
  42   }
  43 }
  44
  45 void MaxMin::do_solve()
  46 {
  47   XBT_IN("(sys=%p)", this);
  48   /* Compute Usage and store the variables that reach the maximum. If selective_update_active is true, only
  49    * constraints that changed are considered. Otherwise all constraints with active actions are considered.
  50    */
  51   if (selective_update_active)
  52     maxmin_solve(modified_constraint_set);
  53   else
  54     maxmin_solve(active_constraint_set);
  55   XBT_OUT();
  56 }
  57
  58 template <class CnstList> void MaxMin::maxmin_solve(CnstList& cnst_list)
  59 {
  60   double min_usage = -1;
  61   double min_bound = -1;
  62
  63   XBT_DEBUG("Active constraints : %zu", cnst_list.size());
  64   cnst_light_vec.reserve(cnst_list.size());
  65   ConstraintLight* cnst_light_tab = cnst_light_vec.data();
  66   int cnst_light_num              = 0;
  67
  68   for (Constraint& cnst : cnst_list) {
  69     /* INIT: Collect constraints that actually need to be saturated (i.e remaining  and usage are strictly positive)
  70      * into cnst_light_tab. */
  71     cnst.dynamic_bound_ = cnst.bound_;
  72     if ((cnst.get_sharing_policy() == Constraint::SharingPolicy::NONLINEAR || cnst.get_sharing_policy() == Constraint::SharingPolicy::WIFI) && cnst.dyn_constraint_cb_) {
  73       cnst.dynamic_bound_ = cnst.dyn_constraint_cb_(cnst.bound_, cnst.concurrency_current_);
  74     }
  75     cnst.remaining_ = cnst.dynamic_bound_;
  76     if (not double_positive(cnst.remaining_, cnst.dynamic_bound_ * sg_precision_workamount))
  77       continue;
  78     cnst.usage_ = 0;
  79     for (Element& elem : cnst.enabled_element_set_) {
  80       xbt_assert(elem.variable->sharing_penalty_ > 0.0);
  81       elem.variable->value_ = 0.0;
  82       if (elem.consumption_weight > 0) {
  83         if (cnst.sharing_policy_ != Constraint::SharingPolicy::FATPIPE)
  84           cnst.usage_ += elem.consumption_weight / elem.variable->sharing_penalty_;
  85         else if (cnst.usage_ < elem.consumption_weight / elem.variable->sharing_penalty_)
  86           cnst.usage_ = elem.consumption_weight / elem.variable->sharing_penalty_;
  87
  88         elem.make_active();
  89       }
  90     }
  91     XBT_DEBUG("Constraint '%d' usage: %f remaining: %f concurrency: %i<=%i<=%i", cnst.rank_, cnst.usage_,
  92               cnst.remaining_, cnst.concurrency_current_, cnst.concurrency_maximum_, cnst.get_concurrency_limit());
  93     /* Saturated constraints update */
  94
  95     if (cnst.usage_ > 0) {
  96       cnst_light_tab[cnst_light_num].cnst                 = &cnst;
  97       cnst.cnst_light_                                    = &cnst_light_tab[cnst_light_num];
  98       cnst_light_tab[cnst_light_num].remaining_over_usage = cnst.remaining_ / cnst.usage_;
  99       saturated_constraints_update(cnst_light_tab[cnst_light_num].remaining_over_usage, cnst_light_num,
 100                                    saturated_constraints, &min_usage);
 101       xbt_assert(not cnst.active_element_set_.empty(),
 102                  "There is no sense adding a constraint that has no active element!");
 103       cnst_light_num++;
 104     }
 105   }
 106
 107   saturated_variable_set_update(cnst_light_tab, saturated_constraints, this);
 108
 109   /* Saturated variables update */
 110   do {
 111     /* Fix the variables that have to be */
 112     auto& var_list = saturated_variable_set;
 113     for (Variable const& var : var_list) {
 114       if (var.sharing_penalty_ <= 0.0)
 115         DIE_IMPOSSIBLE;
 116       /* First check if some of these variables could reach their upper bound and update min_bound accordingly. */
 117       XBT_DEBUG("var=%d, var.bound=%f, var.penalty=%f, min_usage=%f, var.bound*var.penalty=%f", var.rank_, var.bound_,
 118                 var.sharing_penalty_, min_usage, var.bound_ * var.sharing_penalty_);
 119       if ((var.bound_ > 0) && (var.bound_ * var.sharing_penalty_ < min_usage)) {
 120         if (min_bound < 0)
 121           min_bound = var.bound_ * var.sharing_penalty_;
 122         else
 123           min_bound = std::min(min_bound, (var.bound_ * var.sharing_penalty_));
 124         XBT_DEBUG("Updated min_bound=%f", min_bound);
 125       }
 126     }
 127
 128     while (not var_list.empty()) {
 129       Variable& var = var_list.front();
 130       if (min_bound < 0) {
 131         // If no variable could reach its bound, deal iteratively the constraints usage ( at worst one constraint is
 132         // saturated at each cycle)
 133         var.value_ = min_usage / var.sharing_penalty_;
 134         XBT_DEBUG("Setting var (%d) value to %f\n", var.rank_, var.value_);
 135       } else {
 136         // If there exist a variable that can reach its bound, only update it (and other with the same bound) for now.
 137         if (double_equals(min_bound, var.bound_ * var.sharing_penalty_, sg_precision_workamount)) {
 138           var.value_ = var.bound_;
 139           XBT_DEBUG("Setting %p (%d) value to %f\n", &var, var.rank_, var.value_);
 140         } else {
 141           // Variables which bound is different are not considered for this cycle, but they will be afterwards.
 142           XBT_DEBUG("Do not consider %p (%d)\n", &var, var.rank_);
 143           var_list.pop_front();
 144           continue;
 145         }
 146       }
 147       XBT_DEBUG("Min usage: %f, Var(%d).penalty: %f, Var(%d).value: %f", min_usage, var.rank_, var.sharing_penalty_,
 148                 var.rank_, var.value_);
 149
 150       /* Update the usage of constraints where this variable is involved */
 151       for (Element& elem : var.cnsts_) {
 152         Constraint* cnst = elem.constraint;
 153         if (cnst->sharing_policy_ != Constraint::SharingPolicy::FATPIPE) {
 154           // Remember: shared constraints require that sum(elem.value * var.value) < cnst->bound
 155           double_update(&(cnst->remaining_), elem.consumption_weight * var.value_,
 156                         cnst->dynamic_bound_ * sg_precision_workamount);
 157           double_update(&(cnst->usage_), elem.consumption_weight / var.sharing_penalty_, sg_precision_workamount);
 158           // If the constraint is saturated, remove it from the set of active constraints (light_tab)
 159           if (not double_positive(cnst->usage_, sg_precision_workamount) ||
 160               not double_positive(cnst->remaining_, cnst->dynamic_bound_ * sg_precision_workamount)) {
 161             if (cnst->cnst_light_) {
 162               size_t index = (cnst->cnst_light_ - cnst_light_tab);
 163               XBT_DEBUG("index: %zu \t cnst_light_num: %d \t || usage: %f remaining: %f bound: %f", index,
 164                         cnst_light_num, cnst->usage_, cnst->remaining_, cnst->dynamic_bound_);
 165               cnst_light_tab[index]                   = cnst_light_tab[cnst_light_num - 1];
 166               cnst_light_tab[index].cnst->cnst_light_ = &cnst_light_tab[index];
 167               cnst_light_num--;
 168               cnst->cnst_light_ = nullptr;
 169             }
 170           } else {
 171             if (cnst->cnst_light_) {
 172               cnst->cnst_light_->remaining_over_usage = cnst->remaining_ / cnst->usage_;
 173             }
 174           }
 175           elem.make_inactive();
 176         } else {
 177           // Remember: non-shared constraints only require that max(elem.value * var.value) < cnst->bound
 178           cnst->usage_ = 0.0;
 179           elem.make_inactive();
 180           for (const Element& elem2 : cnst->enabled_element_set_) {
 181             xbt_assert(elem2.variable->sharing_penalty_ > 0);
 182             if (elem2.variable->value_ > 0)
 183               continue;
 184             if (elem2.consumption_weight > 0)
 185               cnst->usage_ = std::max(cnst->usage_, elem2.consumption_weight / elem2.variable->sharing_penalty_);
 186           }
 187           // If the constraint is saturated, remove it from the set of active constraints (light_tab)
 188           if (not double_positive(cnst->usage_, sg_precision_workamount) ||
 189               not double_positive(cnst->remaining_, cnst->dynamic_bound_ * sg_precision_workamount)) {
 190             if (cnst->cnst_light_) {
 191               size_t index = (cnst->cnst_light_ - cnst_light_tab);
 192               XBT_DEBUG("index: %zu \t cnst_light_num: %d \t || \t cnst: %p \t cnst->cnst_light: %p "
 193                         "\t cnst_light_tab: %p usage: %f remaining: %f bound: %f",
 194                         index, cnst_light_num, cnst, cnst->cnst_light_, cnst_light_tab, cnst->usage_, cnst->remaining_,
 195                         cnst->dynamic_bound_);
 196               cnst_light_tab[index]                   = cnst_light_tab[cnst_light_num - 1];
 197               cnst_light_tab[index].cnst->cnst_light_ = &cnst_light_tab[index];
 198               cnst_light_num--;
 199               cnst->cnst_light_ = nullptr;
 200             }
 201           } else {
 202             if (cnst->cnst_light_) {
 203               cnst->cnst_light_->remaining_over_usage = cnst->remaining_ / cnst->usage_;
 204               xbt_assert(not cnst->active_element_set_.empty(),
 205                          "Should not keep a maximum constraint that has no active"
 206                          " element! You want to check the maxmin precision and possible rounding effects.");
 207             }
 208           }
 209         }
 210       }
 211       var_list.pop_front();
 212     }
 213
 214     /* Find out which variables reach the maximum */
 215     min_usage = -1;
 216     min_bound = -1;
 217     saturated_constraints.clear();
 218     for (int pos = 0; pos < cnst_light_num; pos++) {
 219       xbt_assert(
 220           not cnst_light_tab[pos].cnst->active_element_set_.empty(),
 221           "Cannot saturate more a constraint that has"
 222           " no active element! You may want to change the work amount precision (--cfg=maxmin/precision:<new_value>)"
 223           " because of possible rounding effects.\n\tFor the record, the usage of this constraint is %g while "
 224           "the maxmin precision to which it is compared is %g.\n\tThe usage of the previous constraint is %g.",
 225           cnst_light_tab[pos].cnst->usage_, sg_precision_workamount, cnst_light_tab[pos - 1].cnst->usage_);
 226       saturated_constraints_update(cnst_light_tab[pos].remaining_over_usage, pos, saturated_constraints, &min_usage);
 227     }
 228
 229     saturated_variable_set_update(cnst_light_tab, saturated_constraints, this);
 230   } while (cnst_light_num > 0);
 231 }
 232
 233 } // namespace simgrid::kernel::lmm