Tpetra: Reduce device-to-host memcpy calls in non-uvm builds

packages/tpetra/core/src/Tpetra_CrsGraph_decl.hpp

@@ -2143,6 +2143,16 @@ namespace Tpetra {
                        typename row_ptrs_device_view_type::host_mirror_space(),
                        dview);
     }
+
+    // There are common cases where both packed and unpacked views are set to the same array.
+    // Doing this in a single call can reduce dataspace on host, and reduce runtime by
+    // removing a deep_copy from device to host.
+
+    void setRowPtrs(const row_ptrs_device_view_type &dview) {
+      setRowPtrsUnpacked(dview);
+      rowPtrsPacked_dev_ = rowPtrsUnpacked_dev_;
+      rowPtrsPacked_host_ = rowPtrsUnpacked_host_;
+    }
 
     //TODO:  Make private -- matrix shouldn't access directly the guts of graph
 

packages/tpetra/core/src/Tpetra_CrsGraph_def.hpp

@@ -683,8 +683,7 @@ namespace Tpetra {
 
     lclIndsPacked_wdv = local_inds_wdv_type(k_local_graph_.entries);
     lclIndsUnpacked_wdv = lclIndsPacked_wdv;
-    this->setRowPtrsUnpacked(k_local_graph_.row_map);
-    this->setRowPtrsPacked(k_local_graph_.row_map);
+    this->setRowPtrs(k_local_graph_.row_map);
 
     set_need_sync_host_uvm_access(); // lclGraph_ potentially still in a kernel
 
@@ -730,8 +729,7 @@ namespace Tpetra {
 
     lclIndsPacked_wdv = local_inds_wdv_type(lclGraph.entries);
     lclIndsUnpacked_wdv = lclIndsPacked_wdv;
-    setRowPtrsUnpacked(lclGraph.row_map);
-    setRowPtrsPacked(lclGraph.row_map);
+    setRowPtrs(lclGraph.row_map);
 
     set_need_sync_host_uvm_access(); // lclGraph_ potentially still in a kernel
 
@@ -2664,6 +2662,8 @@ namespace Tpetra {
   setAllIndices (const typename local_graph_device_type::row_map_type& rowPointers,
                  const typename local_graph_device_type::entries_type::non_const_type& columnIndices)
   {
+    using ProfilingRegion=Details::ProfilingRegion;
+    ProfilingRegion region ("Tpetra::CrsGraph::setAllIndices");
     const char tfecfFuncName[] = "setAllIndices: ";
     TEUCHOS_TEST_FOR_EXCEPTION_CLASS_FUNC(
       ! hasColMap () || getColMap ().is_null (), std::runtime_error,
@@ -2754,8 +2754,7 @@ namespace Tpetra {
     noRedundancies_      = true;
     lclIndsPacked_wdv= local_inds_wdv_type(columnIndices);
     lclIndsUnpacked_wdv          = lclIndsPacked_wdv;
-    setRowPtrsUnpacked(rowPointers);
-    setRowPtrsPacked(rowPointers);
+    setRowPtrs(rowPointers);
 
     set_need_sync_host_uvm_access(); // columnIndices and rowPointers potentially still in a kernel
 
@@ -3652,11 +3651,16 @@ namespace Tpetra {
         }
       }
       // Build the local graph.
-      setRowPtrsPacked(ptr_d_const);
+      if (requestOptimizedStorage)
+        setRowPtrs(ptr_d_const);
+      else
+        setRowPtrsPacked(ptr_d_const);
       lclIndsPacked_wdv = local_inds_wdv_type(ind_d);
     }
     else { // We don't have to pack, so just set the pointers.
-      setRowPtrsPacked(rowPtrsUnpacked_dev_);
+      // Note: The setRowPtrsPacked call has an aditional memcpy to host that we want to avoid
+      rowPtrsPacked_dev_ = rowPtrsUnpacked_dev_;
+      rowPtrsPacked_host_ = rowPtrsUnpacked_host_;
       lclIndsPacked_wdv = lclIndsUnpacked_wdv; 
 
       if (debug_) {
@@ -3708,7 +3712,6 @@ namespace Tpetra {
       k_numRowEntries_ = row_entries_type ();
 
       // Keep the new 1-D packed allocations.
-      setRowPtrsUnpacked(rowPtrsPacked_dev_);
       lclIndsUnpacked_wdv = lclIndsPacked_wdv;
 
       storageStatus_ = Details::STORAGE_1D_PACKED;

packages/tpetra/core/src/Tpetra_CrsMatrix_def.hpp

@@ -1214,7 +1214,7 @@ namespace Tpetra {
     using lclinds_1d_type = typename Graph::local_graph_device_type::entries_type::non_const_type;
     using values_type = typename local_matrix_device_type::values_type;
     Details::ProfilingRegion regionFLGAM
-      ("Tpetra::CrsGraph::fillLocalGraphAndMatrix");
+      ("Tpetra::CrsMatrix::fillLocalGraphAndMatrix");
 
     const char tfecfFuncName[] = "fillLocalGraphAndMatrix (called from "
       "fillComplete or expertStaticFillComplete): ";
@@ -1454,7 +1454,9 @@ namespace Tpetra {
     }
     else { // We don't have to pack, so just set the pointers.
       // FIXME KDDKDD https://github.com/trilinos/Trilinos/issues/9657
-      myGraph_->setRowPtrsPacked(myGraph_->rowPtrsUnpacked_dev_);
+      // FIXME? This is already done in the graph fill call - need to avoid the memcpy to host
+      myGraph_->rowPtrsPacked_dev_ = myGraph_->rowPtrsUnpacked_dev_;
+      myGraph_->rowPtrsPacked_host_ = myGraph_->rowPtrsUnpacked_host_;
       myGraph_->lclIndsPacked_wdv = myGraph_->lclIndsUnpacked_wdv;
       valuesPacked_wdv = valuesUnpacked_wdv;
 
@@ -1547,7 +1549,9 @@ namespace Tpetra {
 
       // Keep the new 1-D packed allocations.
       // FIXME KDDKDD https://github.com/trilinos/Trilinos/issues/9657
-      myGraph_->setRowPtrsUnpacked(myGraph_->rowPtrsPacked_dev_);
+      // We directly set the memory spaces to avoid a memcpy from device to host
+      myGraph_->rowPtrsUnpacked_dev_ = myGraph_->rowPtrsPacked_dev_;
+      myGraph_->rowPtrsUnpacked_host_ = myGraph_->rowPtrsPacked_host_;
       myGraph_->lclIndsUnpacked_wdv = myGraph_->lclIndsPacked_wdv;
       valuesUnpacked_wdv = valuesPacked_wdv;
 
@@ -3438,6 +3442,8 @@ CrsMatrix<Scalar, LocalOrdinal, GlobalOrdinal, Node>::
                 const typename local_graph_device_type::entries_type::non_const_type& columnIndices,
                 const typename local_matrix_device_type::values_type& values)
   {
+    using ProfilingRegion=Details::ProfilingRegion;
+    ProfilingRegion region ("Tpetra::CrsMatrix::setAllValues");
     const char tfecfFuncName[] = "setAllValues: ";
     TEUCHOS_TEST_FOR_EXCEPTION_CLASS_FUNC
       (columnIndices.size () != values.size (), std::invalid_argument,
@@ -3454,6 +3460,7 @@ CrsMatrix<Scalar, LocalOrdinal, GlobalOrdinal, Node>::
         (true, std::runtime_error, "myGraph_->setAllIndices() threw an "
          "exception: " << e.what ());
     }
+
     // Make sure that myGraph_ now has a local graph.  It may not be
     // fillComplete yet, so it's important to check.  We don't care
     // whether setAllIndices() did a shallow copy or a deep copy, so a

packages/tpetra/core/src/Tpetra_Details_WrappedDualView.hpp

@@ -167,11 +167,14 @@ class WrappedDualView {
     t_host hostView;
     if(deviceView.use_count() != 0)
     {
-      hostView = Kokkos::create_mirror_view_and_copy(
+      hostView = Kokkos::create_mirror_view(
+          Kokkos::WithoutInitializing,
           typename t_host::memory_space(),
           deviceView);
     }
     originalDualView = DualViewType(deviceView, hostView);
+    originalDualView.clear_sync_state();
+    originalDualView.modify_device();
     dualView = originalDualView;
   }
 

packages/tpetra/core/src/Tpetra_MultiVector_def.hpp

@@ -217,14 +217,7 @@ namespace { // (anonymous)
          << ".  Please report this bug to the Tpetra developers.");
     }
 
-    dual_view_type dv (d_view, Kokkos::create_mirror_view (d_view));
-    // Whether or not the user cares about the initial contents of the
-    // MultiVector, the device and host views are out of sync.  We
-    // prefer to work in device memory.  The way to ensure this
-    // happens is to mark the device view as modified.
-    dv.modify_device ();
-
-    return wrapped_dual_view_type(dv);
+    return wrapped_dual_view_type(d_view);
   }
 
   // Convert 1-D Teuchos::ArrayView to an unmanaged 1-D host Kokkos::View.

packages/tpetra/core/test/Block/BlockMultiVector.cpp

@@ -428,7 +428,7 @@ namespace {
     {
       auto X_overlap =
         X.getLocalBlockHost (meshMap.getLocalElement (meshMap.getMinGlobalIndex ()), 
-                         colToModify, Tpetra::Access::OverwriteAll);
+                         colToModify, Tpetra::Access::ReadWrite);
       TEST_ASSERT( X_overlap.data () != NULL );
       TEST_EQUALITY_CONST( static_cast<size_t> (X_overlap.extent (0)),
                            static_cast<size_t> (blockSize) );
@@ -466,6 +466,7 @@ namespace {
              localMeshRow < meshMap.getMaxLocalIndex (); ++localMeshRow) {
           auto Y_cur = Y.getLocalBlockHost (localMeshRow, col,
                                         Tpetra::Access::ReadOnly);
+
           if (col != colToModify) {
             TEST_ASSERT( equal (Y_cur, zeroLittleVector) &&
                          equal (zeroLittleVector, Y_cur) );