1 files changed, 75 insertions, 0 deletions
diff --git a/libgomp/testsuite/libgomp.fortran/strassen.f90 b/libgomp/testsuite/libgomp.fortran/strassen.f90
new file mode 100644
index 000000000..b44982665
--- /dev/null
+++ b/libgomp/testsuite/libgomp.fortran/strassen.f90
@@ -0,0 +1,75 @@
+! { dg-options "-O2" }
+
+program strassen_matmul
+  use omp_lib
+  integer, parameter :: N = 1024
+  double precision, save :: A(N,N), B(N,N), C(N,N), D(N,N)
+  double precision :: start, end
+
+  call random_seed
+  call random_number (A)
+  call random_number (B)
+  start = omp_get_wtime ()
+  C = matmul (A, B)
+  end = omp_get_wtime ()
+  write(*,'(a, f10.6)') ' Time for matmul      = ', end - start
+  D = 0
+  start = omp_get_wtime ()
+  call strassen (A, B, D, N)
+  end = omp_get_wtime ()
+  write(*,'(a, f10.6)') ' Time for Strassen    = ', end - start
+  if (sqrt (sum ((C - D) ** 2)) / N .gt. 0.1) call abort
+  D = 0
+  start = omp_get_wtime ()
+!$omp parallel
+!$omp single
+  call strassen (A, B, D, N)
+!$omp end single nowait
+!$omp end parallel
+  end = omp_get_wtime ()
+  write(*,'(a, f10.6)') ' Time for Strassen MP = ', end - start
+  if (sqrt (sum ((C - D) ** 2)) / N .gt. 0.1) call abort
+
+contains
+
+  recursive subroutine strassen (A, B, C, N)
+    integer, intent(in) :: N
+    double precision, intent(in) :: A(N,N), B(N,N)
+    double precision, intent(out) :: C(N,N)
+    double precision :: T(N/2,N/2,7)
+    integer :: K, L
+
+    if (iand (N,1) .ne. 0 .or. N < 64) then
+      C = matmul (A, B)
+      return
+    end if
+    K = N / 2
+    L = N / 2 + 1
+!$omp task shared (A, B, T)
+    call strassen (A(:K,:K) + A(L:,L:), B(:K,:K) + B(L:,L:), T(:,:,1), K)
+!$omp end task
+!$omp task shared (A, B, T)
+    call strassen (A(L:,:K) + A(L:,L:), B(:K,:K), T(:,:,2), K)
+!$omp end task
+!$omp task shared (A, B, T)
+    call strassen (A(:K,:K), B(:K,L:) - B(L:,L:), T(:,:,3), K)
+!$omp end task
+!$omp task shared (A, B, T)
+    call strassen (A(L:,L:), B(L:,:K) - B(:K,:K), T(:,:,4), K)
+!$omp end task
+!$omp task shared (A, B, T)
+    call strassen (A(:K,:K) + A(:K,L:), B(L:,L:), T(:,:,5), K)
+!$omp end task
+!$omp task shared (A, B, T)
+    call strassen (A(L:,:K) - A(:K,:K), B(:K,:K) + B(:K,L:), T(:,:,6), K)
+!$omp end task
+!$omp task shared (A, B, T)
+    call strassen (A(:K,L:) - A(L:,L:), B(L:,:K) + B(L:,L:), T(:,:,7), K)
+!$omp end task
+!$omp taskwait
+    C(:K,:K) = T(:,:,1) + T(:,:,4) - T(:,:,5) + T(:,:,7)
+    C(L:,:K) = T(:,:,2) + T(:,:,4)
+    C(:K,L:) = T(:,:,3) + T(:,:,5)
+    C(L:,L:) = T(:,:,1) - T(:,:,2) + T(:,:,3) + T(:,:,6)
+  end subroutine strassen
+end