Add config option to set busy wait timeout in tridiagonal solver rank…

…1 problem

include/dlaf/eigensolver/internal/get_tridiag_rank1_barrier_busy_wait.h

@@ -0,0 +1,22 @@
+//
+// Distributed Linear Algebra with Future (DLAF)
+//
+// Copyright (c) 2018-2023, ETH Zurich
+// All rights reserved.
+//
+// Please, refer to the LICENSE file in the root directory.
+// SPDX-License-Identifier: BSD-3-Clause
+//
+#pragma once
+
+#include <chrono>
+
+#include "dlaf/tune.h"
+
+namespace dlaf::eigensolver::internal {
+
+inline std::chrono::duration<double> getTridiagRank1BarrierBusyWait() noexcept {
+  return std::chrono::microseconds(getTuneParameters().red2band_barrier_busy_wait_us);
+}
+
+}

include/dlaf/eigensolver/tridiag_solver/merge.h

@@ -17,6 +17,7 @@
 #include <dlaf/common/range2d.h>
 #include <dlaf/common/single_threaded_blas.h>
 #include <dlaf/communication/kernels.h>
+#include <dlaf/eigensolver/internal/get_tridiag_rank1_barrier_busy_wait.h>
 #include <dlaf/eigensolver/internal/get_tridiag_rank1_nworkers.h>
 #include <dlaf/eigensolver/tridiag_solver/coltype.h>
 #include <dlaf/eigensolver/tridiag_solver/index_manipulation.h>
@@ -475,6 +476,7 @@ void solveRank1Problem(const SizeType i_begin, const SizeType i_end, KSender&& k
                                            auto& evec_tiles, auto& ws_vecs) {
         const matrix::Distribution distr(LocalElementSize(n, n), TileElementSize(nb, nb));
 
+        const auto barrier_busy_wait = getTridiagRank1BarrierBusyWait();
         const std::size_t batch_size = util::ceilDiv(to_sizet(k), nthreads);
         const std::size_t begin = thread_idx * batch_size;
         const std::size_t end = std::min(thread_idx * batch_size + batch_size, to_sizet(k));
@@ -486,7 +488,7 @@ void solveRank1Problem(const SizeType i_begin, const SizeType i_end, KSender&& k
             ws_vecs.emplace_back(to_sizet(k));
         }
 
-        barrier_ptr->arrive_and_wait();
+        barrier_ptr->arrive_and_wait(barrier_busy_wait);
 
         // STEP 1: LAED4 (multi-thread)
         const T* d_ptr = d_tiles_futs[0].get().ptr();
@@ -511,7 +513,7 @@ void solveRank1Problem(const SizeType i_begin, const SizeType i_end, KSender&& k
             return;
         }
 
-        barrier_ptr->arrive_and_wait();
+        barrier_ptr->arrive_and_wait(barrier_busy_wait);
 
         // STEP 2a Compute weights (multi-thread)
         auto& q = evec_tiles;
@@ -550,7 +552,7 @@ void solveRank1Problem(const SizeType i_begin, const SizeType i_end, KSender&& k
             compute_w({i, j});
         }
 
-        barrier_ptr->arrive_and_wait();
+        barrier_ptr->arrive_and_wait(barrier_busy_wait);
 
         // STEP 2B: reduce, then finalize computation with sign and square root (single-thread)
         if (thread_idx == 0) {
@@ -563,7 +565,7 @@ void solveRank1Problem(const SizeType i_begin, const SizeType i_end, KSender&& k
           }
         }
 
-        barrier_ptr->arrive_and_wait();
+        barrier_ptr->arrive_and_wait(barrier_busy_wait);
 
         // STEP 3: Compute eigenvectors of the modified rank-1 modification (normalize) (multi-thread)
         {

include/dlaf/tune.h

@@ -30,6 +30,10 @@ namespace dlaf {
 /// - tridiag_rank1_nworkers:
 ///     The maximum number of threads to use for computing rank1 problem solution in tridiagonal solver
 ///     algorithm. Set with --dlaf:tridiag-rank1-nworkers or env variable DLAF_TRIDIAG_RANK1_NWORKERS.
+/// - tridiag_rank1_barrier_busy_wait_us:
+///     The duration in microseconds to busy-wait in barriers when computing rank1 problem solution in
+///     the tridiagonal solver algorithm. Set with --dlaf:tridiag-rank1-barrier-busy-wait-us or env
+///     variable DLAF_TRIDIAG_RANK1_BARRIER_BUSY_WAIT_US.
 /// - eigensolver_min_band:
 ///     The minimum value to start looking for a divisor of the block size.
 ///     Set with --dlaf:eigensolver-min-band or env variable DLAF_EIGENSOLVER_MIN_BAND.
@@ -50,6 +54,7 @@ struct TuneParameters {
   std::size_t red2band_barrier_busy_wait_us = 1000;
   std::size_t tridiag_rank1_nworkers =
       std::max<std::size_t>(1, pika::resource::get_thread_pool("default").get_os_thread_count() / 2);
+  std::size_t tridiag_rank1_barrier_busy_wait_us = 0;
 
   SizeType eigensolver_min_band = 100;
   SizeType band_to_tridiag_1d_block_size_base = 8192;

src/init.cpp

@@ -174,6 +174,9 @@ void updateConfiguration(const pika::program_options::variables_map& vm, configu
   updateConfigurationValue(vm, param.tridiag_rank1_nworkers, "TRIDIAG_RANK1_NWORKERS",
                            "tridiag-rank1-nworkers");
 
+  updateConfigurationValue(vm, param.red2band_barrier_busy_wait_us, "TRIDIAG_RANK1_BARRIER_BUSY_WAIT_US",
+                           "tridiag-rank1-barrier-busy-wait-us");
+
   updateConfigurationValue(vm, param.bt_band_to_tridiag_hh_apply_group_size,
                            "DLAF_BT_BAND_TO_TRIDIAG_HH_APPLY_GROUP_SIZE",
                            "bt-band-to-tridiag-hh-apply-group-size");
@@ -218,6 +221,9 @@ pika::program_options::options_description getOptionsDescription() {
   desc.add_options()(
       "dlaf:tridiag-rank1-nworkers", pika::program_options::value<std::size_t>(),
       "The maximum number of threads to use for computing rank1 problem solution in tridiagonal solver algorithm.");
+  desc.add_options()(
+      "dlaf:tridiag-rank1-barrier-busy-wait-us", pika::program_options::value<std::size_t>(),
+      "The duration in microseconds to busy-wait in barriers when computing rank1 problem solution in the tridiagonal solver algorithm.");
   desc.add_options()(
       "dlaf:bt-band-to-tridiag-hh-apply-group-size", pika::program_options::value<SizeType>(),
       "The application of the HH reflector is splitted in smaller applications of group size reflectors.");