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Diffstat (limited to 'intern/cycles/integrator/work_balancer.cpp')
-rw-r--r-- | intern/cycles/integrator/work_balancer.cpp | 99 |
1 files changed, 99 insertions, 0 deletions
diff --git a/intern/cycles/integrator/work_balancer.cpp b/intern/cycles/integrator/work_balancer.cpp new file mode 100644 index 00000000000..9f96fe3632b --- /dev/null +++ b/intern/cycles/integrator/work_balancer.cpp @@ -0,0 +1,99 @@ +/* + * Copyright 2011-2021 Blender Foundation + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#include "integrator/work_balancer.h" + +#include "util/util_math.h" + +#include "util/util_logging.h" + +CCL_NAMESPACE_BEGIN + +void work_balance_do_initial(vector<WorkBalanceInfo> &work_balance_infos) +{ + const int num_infos = work_balance_infos.size(); + + if (num_infos == 1) { + work_balance_infos[0].weight = 1.0; + return; + } + + /* There is no statistics available, so start with an equal distribution. */ + const double weight = 1.0 / num_infos; + for (WorkBalanceInfo &balance_info : work_balance_infos) { + balance_info.weight = weight; + } +} + +static double calculate_total_time(const vector<WorkBalanceInfo> &work_balance_infos) +{ + double total_time = 0; + for (const WorkBalanceInfo &info : work_balance_infos) { + total_time += info.time_spent; + } + return total_time; +} + +/* The balance is based on equalizing time which devices spent performing a task. Assume that + * average of the observed times is usable for estimating whether more or less work is to be + * scheduled, and how difference in the work scheduling is needed. */ + +bool work_balance_do_rebalance(vector<WorkBalanceInfo> &work_balance_infos) +{ + const int num_infos = work_balance_infos.size(); + + const double total_time = calculate_total_time(work_balance_infos); + const double time_average = total_time / num_infos; + + double total_weight = 0; + vector<double> new_weights; + new_weights.reserve(num_infos); + + /* Equalize the overall average time. This means that we don't make it so every work will perform + * amount of work based on the current average, but that after the weights changes the time will + * equalize. + * Can think of it that if one of the devices is 10% faster than another, then one device needs + * to do 5% less of the current work, and another needs to do 5% more. */ + const double lerp_weight = 1.0 / num_infos; + + bool has_big_difference = false; + + for (const WorkBalanceInfo &info : work_balance_infos) { + const double time_target = lerp(info.time_spent, time_average, lerp_weight); + const double new_weight = info.weight * time_target / info.time_spent; + new_weights.push_back(new_weight); + total_weight += new_weight; + + if (std::fabs(1.0 - time_target / time_average) > 0.02) { + has_big_difference = true; + } + } + + if (!has_big_difference) { + return false; + } + + const double total_weight_inv = 1.0 / total_weight; + for (int i = 0; i < num_infos; ++i) { + WorkBalanceInfo &info = work_balance_infos[i]; + info.weight = new_weights[i] * total_weight_inv; + info.time_spent = 0; + } + + return true; +} + +CCL_NAMESPACE_END |