9cfc7967dd
* Replace license text in headers with SPDX identifiers. * Remove specific license info from outdated readme.txt, instead leave details to the source files. * Add list of SPDX license identifiers used, and corresponding license texts. * Update copyright dates while we're at it. Ref D14069, T95597
87 lines
2.6 KiB
C++
87 lines
2.6 KiB
C++
/* SPDX-License-Identifier: Apache-2.0
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* Copyright 2011-2022 Blender Foundation */
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#include "integrator/work_balancer.h"
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#include "util/math.h"
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#include "util/log.h"
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CCL_NAMESPACE_BEGIN
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void work_balance_do_initial(vector<WorkBalanceInfo> &work_balance_infos)
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{
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const int num_infos = work_balance_infos.size();
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if (num_infos == 1) {
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work_balance_infos[0].weight = 1.0;
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return;
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}
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/* There is no statistics available, so start with an equal distribution. */
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const double weight = 1.0 / num_infos;
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for (WorkBalanceInfo &balance_info : work_balance_infos) {
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balance_info.weight = weight;
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}
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}
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static double calculate_total_time(const vector<WorkBalanceInfo> &work_balance_infos)
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{
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double total_time = 0;
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for (const WorkBalanceInfo &info : work_balance_infos) {
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total_time += info.time_spent;
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}
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return total_time;
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}
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/* The balance is based on equalizing time which devices spent performing a task. Assume that
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* average of the observed times is usable for estimating whether more or less work is to be
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* scheduled, and how difference in the work scheduling is needed. */
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bool work_balance_do_rebalance(vector<WorkBalanceInfo> &work_balance_infos)
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{
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const int num_infos = work_balance_infos.size();
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const double total_time = calculate_total_time(work_balance_infos);
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const double time_average = total_time / num_infos;
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double total_weight = 0;
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vector<double> new_weights;
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new_weights.reserve(num_infos);
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/* Equalize the overall average time. This means that we don't make it so every work will perform
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* amount of work based on the current average, but that after the weights changes the time will
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* equalize.
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* Can think of it that if one of the devices is 10% faster than another, then one device needs
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* to do 5% less of the current work, and another needs to do 5% more. */
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const double lerp_weight = 1.0 / num_infos;
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bool has_big_difference = false;
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for (const WorkBalanceInfo &info : work_balance_infos) {
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const double time_target = lerp(info.time_spent, time_average, lerp_weight);
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const double new_weight = info.weight * time_target / info.time_spent;
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new_weights.push_back(new_weight);
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total_weight += new_weight;
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if (std::fabs(1.0 - time_target / time_average) > 0.02) {
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has_big_difference = true;
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}
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}
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if (!has_big_difference) {
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return false;
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}
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const double total_weight_inv = 1.0 / total_weight;
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for (int i = 0; i < num_infos; ++i) {
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WorkBalanceInfo &info = work_balance_infos[i];
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info.weight = new_weights[i] * total_weight_inv;
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info.time_spent = 0;
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}
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return true;
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}
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CCL_NAMESPACE_END
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