ifpack2: Remove Kokkos::subview calls from ComputeResidualVector kernel.

This fixes a large performance regression seen in SPARC after the kokkos-3.6.01 promotion, see issue kokkos/kokkos#6533.
trilinos · Oct 24, 2023 · a877537 · a877537
1 parent dcd4ed5
commit a877537
Showing 1 changed file with 12 additions and 8 deletions.
diff --git a/packages/ifpack2/src/Ifpack2_BlockTriDiContainer_impl.hpp b/packages/ifpack2/src/Ifpack2_BlockTriDiContainer_impl.hpp
@@ -3466,10 +3466,12 @@ namespace Ifpack2 {
         const local_ordinal_type num_local_rows = lclrow.extent(0);
 
         // subview pattern
-        auto bb = Kokkos::subview(b, block_range, 0);
-        auto xx = Kokkos::subview(x, block_range, 0);
-        auto xx_remote = Kokkos::subview(x_remote, block_range, 0);
-        auto yy = Kokkos::subview(y_packed_scalar, 0, block_range, 0, 0);
+        using subview_1D_right_t = decltype(Kokkos::subview(b, block_range, 0));
+        subview_1D_right_t bb(nullptr, blocksize);
+        subview_1D_right_t xx(nullptr, blocksize);
+        subview_1D_right_t xx_remote(nullptr, blocksize);
+        using subview_1D_stride_t = decltype(Kokkos::subview(y_packed_scalar, 0, block_range, 0, 0));
+        subview_1D_stride_t yy(nullptr, Kokkos::LayoutStride(blocksize, y_packed_scalar.stride_1()));
         auto A_block = ConstUnmanaged<tpetra_block_access_view_type>(NULL, blocksize, blocksize);
 
         const local_ordinal_type lr = lclrow(rowidx);
@@ -3584,10 +3586,12 @@ namespace Ifpack2 {
         const local_ordinal_type num_local_rows = lclrow.extent(0);
 
         // subview pattern
-        auto bb = Kokkos::subview(b, block_range, 0);
-        auto xx = bb; //Kokkos::subview(x, block_range, 0);
-        auto xx_remote = bb; //Kokkos::subview(x_remote, block_range, 0);
-        auto yy = Kokkos::subview(y_packed_scalar, 0, block_range, 0, 0);
+        using subview_1D_right_t = decltype(Kokkos::subview(b, block_range, 0));
+        subview_1D_right_t bb(nullptr, blocksize);
+        subview_1D_right_t xx(nullptr, blocksize);
+        subview_1D_right_t xx_remote(nullptr, blocksize);
+        using subview_1D_stride_t = decltype(Kokkos::subview(y_packed_scalar, 0, block_range, 0, 0));
+        subview_1D_stride_t yy(nullptr, Kokkos::LayoutStride(blocksize, y_packed_scalar.stride_1()));
         auto A_block = ConstUnmanaged<tpetra_block_access_view_type>(NULL, blocksize, blocksize);
         auto colindsub_used = (P == 0 ? colindsub : colindsub_remote);
         auto rowptr_used = (P == 0 ? rowptr : rowptr_remote);