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Tpetra_KokkosRefactor_Details_MultiVectorLocalDeepCopy.hpp
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43 
44 #ifndef TPETRA_KOKKOS_REFACTOR_DETAILS_MULTI_VECTOR_LOCAL_DEEP_COPY_HPP
45 #define TPETRA_KOKKOS_REFACTOR_DETAILS_MULTI_VECTOR_LOCAL_DEEP_COPY_HPP
46 
47 #include "Kokkos_Core.hpp"
49 
50 namespace Tpetra {
51 namespace Details {
52 
53 namespace { // (anonymous)
54 
55 template<class DstViewType, class SrcViewType>
56 void
57 copyConvertResolvingPossibleAliasing (const DstViewType& dst,
58  const SrcViewType& src)
59 {
60  // NOTE: It's important to do the addition _inside_ the
61  // reinterpret-cast. If you reinterpret_cast the separate results,
62  // you may get the wrong answer (e.g., because ptrdiff_t is signed,
63  // and pointers may have arbitrary 64-bit virtual addresses). I'm
64  // speaking from experience here.
65  const ptrdiff_t dst_beg = reinterpret_cast<ptrdiff_t> (dst.data ());
66  const ptrdiff_t dst_end =
67  reinterpret_cast<ptrdiff_t> (dst.data () + dst.span ());
68  const ptrdiff_t src_beg = reinterpret_cast<ptrdiff_t> (src.data ());
69  const ptrdiff_t src_end =
70  reinterpret_cast<ptrdiff_t> (src.data () + src.span ());
71 
72  if (src_beg == dst_beg && src_end == dst_end) {
73  // Do nothing; there's no need to copy
74  }
75  else if (dst_end <= src_beg || src_end <= dst_beg) { // no aliasing
77  }
78  else {
79  // dst and src alias each other, so we can't call
80  // Kokkos::deep_copy(dst,src) directly (Kokkos detects this and
81  // throws, at least in debug mode). Instead, we make temporary
82  // host storage (create_mirror always makes a new allocation,
83  // unlike create_mirror_view). Use host because it's cheaper to
84  // allocate. Hopefully users aren't doing aliased copies in a
85  // tight loop.
86  auto src_copy = Kokkos::create_mirror (Kokkos::HostSpace (), src);
87 
88  // DEEP_COPY REVIEW - NOT TESTED
89  Kokkos::deep_copy (src_copy, src);
90  ::Tpetra::Details::copyConvert (dst, src_copy);
91  }
92 }
93 
94 } // namespace (anonymous)
95 
129 template<class DstViewType,
130  class SrcViewType,
131  class DstWhichVecsType,
132  class SrcWhichVecsType>
133 void
134 localDeepCopy (const DstViewType& dst,
135  const SrcViewType& src,
136  const bool dstConstStride,
137  const bool srcConstStride,
138  const DstWhichVecsType& dstWhichVecs,
139  const SrcWhichVecsType& srcWhichVecs)
140 {
141  using Kokkos::ALL;
142  using Kokkos::subview;
143  using size_type = typename DstViewType::size_type;
144 
145  if (dstConstStride && srcConstStride) {
146  copyConvertResolvingPossibleAliasing (dst, src);
147  }
148  else {
149  const size_type numCols = dstConstStride ?
150  static_cast<size_type> (srcWhichVecs.size ()) :
151  static_cast<size_type> (dstWhichVecs.size ());
152  for (size_type j = 0; j < numCols; ++j) {
153  const size_type dst_col = dstConstStride ? j :
154  static_cast<size_type> (dstWhichVecs[j]);
155  const auto dst_j = subview (dst, ALL (), dst_col);
156  const size_type src_col = srcConstStride ? j :
157  static_cast<size_type> (srcWhichVecs[j]);
158  const auto src_j = subview (src, ALL (), src_col);
159 
160  copyConvertResolvingPossibleAliasing (dst_j, src_j);
161  }
162  }
163 }
164 
168 template<class DstViewType,
169  class SrcViewType>
170 void
171 localDeepCopyConstStride (const DstViewType& dst,
172  const SrcViewType& src)
173 {
174  return copyConvertResolvingPossibleAliasing (dst, src);
175 }
176 
177 } // Details namespace
178 } // Tpetra namespace
179 
180 #endif // TPETRA_KOKKOS_REFACTOR_DETAILS_MULTI_VECTOR_LOCAL_DEEP_COPY_HPP
void localDeepCopyConstStride(const DstViewType &dst, const SrcViewType &src)
Implementation of Tpetra::MultiVector deep copy of local data, for when both the source and destinati...
Declare and define Tpetra::Details::copyConvert, an implementation detail of Tpetra (in particular...
void deep_copy(MultiVector< DS, DL, DG, DN > &dst, const MultiVector< SS, SL, SG, SN > &src)
Copy the contents of the MultiVector src into dst.
void copyConvert(const OutputViewType &dst, const InputViewType &src)
Copy values from the 1-D Kokkos::View src, to the 1-D Kokkos::View dst, of the same length...
void localDeepCopy(const DstViewType &dst, const SrcViewType &src, const bool dstConstStride, const bool srcConstStride, const DstWhichVecsType &dstWhichVecs, const SrcWhichVecsType &srcWhichVecs)
Implementation of Tpetra::MultiVector deep copy of local data.