Generalize parallel GEMM implementation in Core to work with ThreadPool in addition to OpenMP.

test/product_threaded.cpp

@@ -0,0 +1,33 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2023 Rasmus Munk Larsen <rmlarsen@google.com>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#define EIGEN_GEMM_THREADPOOL
+#include "main.h"
+
+void test_parallelize_gemm() {
+  constexpr int n = 1024;
+  constexpr int num_threads = 4;
+  MatrixXf a(n,n);
+  MatrixXf b(n,n);
+  MatrixXf c(n,n);
+  c.noalias() = a*b;
+
+  ThreadPool pool(num_threads);
+  MatrixXf c_threaded(n,n);
+  c_threaded.noalias() = a*b;
+
+  VERIFY_IS_APPROX(c, c_threaded);
+}
+
+
+
+EIGEN_DECLARE_TEST(product_threaded)
+{
+  CALL_SUBTEST(test_parallelize_gemm());
+}