btas::Tensor can be copied into from Tensor and TensorInterface ... t…

…his allows TA::retile on DistArrays of btas::Tensors

src/TiledArray/external/btas.h

@@ -62,6 +62,13 @@ class boxrange_iteration_order<TiledArray::Range> {
  static constexpr int value = row_major;
 };
 
+template <typename T, typename A>
+class is_tensor<TiledArray::Tensor<T, A>> : public std::true_type {};
+
+template <typename T, typename R, typename O>
+class is_tensor<TiledArray::detail::TensorInterface<T, R, O>>
+ : public std::true_type {};
+
 } // namespace btas
 
 namespace TiledArray {

tests/btas.cpp

@@ -256,6 +256,21 @@ BOOST_AUTO_TEST_CASE_TEMPLATE(tensor_ctor, Tensor, tensor_types) {
  BOOST_REQUIRE_NO_THROW(Tensor t1 = t0);
  Tensor t1 = t0;
  BOOST_CHECK(t1.empty());
+
+ // can copy TA::Tensor to btas::Tensor
+ TA::Tensor<typename Tensor::value_type> ta_tensor(r);
+ BOOST_REQUIRE_NO_THROW(Tensor(ta_tensor));
+ Tensor t2(ta_tensor);
+ for (auto i : r) {
+ BOOST_CHECK_EQUAL(ta_tensor(i), t2(i));
+ }
+
+ // can copy TA::TensorInterface to btas::Tensor
+ BOOST_REQUIRE_NO_THROW(Tensor(ta_tensor.block(r.lobound(), r.upbound())));
+ Tensor t3(ta_tensor.block(r.lobound(), r.upbound()));
+ for (auto i : r) {
+ BOOST_CHECK_EQUAL(ta_tensor(i), t3(i));
+ }
 }
 
 BOOST_AUTO_TEST_CASE_TEMPLATE(copy, Array, array_types) {

tests/expressions_btas.cpp

@@ -23,6 +23,8 @@
  *
  */
 
+#include <TiledArray/config.h>
+
 #ifdef TILEDARRAY_HAS_BTAS
 #include "expressions_fixture.h"