better btas::Tensor interoperation with TA tensorials

INSTALL.md

@@ -41,7 +41,7 @@ Both methods are supported. However, for most users we _strongly_ recommend to b
   - Boost.Test: header-only or (optionally) as a compiled library, *only used for unit testing*
   - Boost.Range: header-only, *only used for unit testing*
 - [Range-V3](https://github.com/ericniebler/range-v3.git) -- a Ranges library that served as the basis for Ranges component of C++20 and later.
-- [BTAS](http://github.com/ValeevGroup/BTAS), tag 4e8f5233aa7881dccdfcc37ce07128833926d3c2 . If usable BTAS installation is not found, TiledArray will download and compile
+- [BTAS](http://github.com/ValeevGroup/BTAS), tag 4b3757cc2b5862f93589afc1e37523e543779c7a . If usable BTAS installation is not found, TiledArray will download and compile
   BTAS from source. *This is the recommended way to compile BTAS for all users*.
 - [MADNESS](https://github.com/m-a-d-n-e-s-s/madness), tag 95589b0d020a076f93d02eead6da654b23dd3d91 .
   Only the MADworld runtime and BLAS/LAPACK C API component of MADNESS is used by TiledArray.

external/versions.cmake

@@ -16,8 +16,8 @@ set(TA_TRACKED_MADNESS_PREVIOUS_TAG 96ac90e8f193ccfaf16f346b4652927d2d362e75)
 set(TA_TRACKED_MADNESS_VERSION 0.10.1)
 set(TA_TRACKED_MADNESS_PREVIOUS_VERSION 0.10.1)
 
-set(TA_TRACKED_BTAS_TAG 4e8f5233aa7881dccdfcc37ce07128833926d3c2)
-set(TA_TRACKED_BTAS_PREVIOUS_TAG b7b2ea7513b087e35c6f1b26184a3904ac1e6b14)
+set(TA_TRACKED_BTAS_TAG 4b3757cc2b5862f93589afc1e37523e543779c7a)
+set(TA_TRACKED_BTAS_PREVIOUS_TAG 4e8f5233aa7881dccdfcc37ce07128833926d3c2)
 
 set(TA_TRACKED_LIBRETT_TAG 6eed30d4dd2a5aa58840fe895dcffd80be7fbece)
 set(TA_TRACKED_LIBRETT_PREVIOUS_TAG 354e0ccee54aeb2f191c3ce2c617ebf437e49d83)

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 {

src/TiledArray/range1.h

@@ -163,8 +163,6 @@ struct Range1 {
   /// \return An iterator that points to the beginning of the local element set
   const_iterator cend() const { return end(); }
 
-  /// @}
-
   /// shifts this Range1
 
   /// @param[in] shift the shift to apply

src/TiledArray/tensor/tensor.h

@@ -1003,7 +1003,7 @@ class Tensor {
 
   /// Iterator factory
 
-  /// \return An iterator to the first data element
+  /// \return A const iterator to the first data element
   const_iterator begin() const { return (this->data() ? this->data() : NULL); }
 
   /// Iterator factory
@@ -1013,7 +1013,7 @@ class Tensor {
 
   /// Iterator factory
 
-  /// \return An iterator to the last data element
+  /// \return A const iterator to the last data element
   const_iterator end() const {
     return (this->data() ? this->data() + this->size() : NULL);
   }
@@ -1023,6 +1023,30 @@ class Tensor {
   /// \return An iterator to the last data element
   iterator end() { return (this->data() ? this->data() + this->size() : NULL); }
 
+  /// Iterator factory
+
+  /// \return A const iterator to the first data element
+  const_iterator cbegin() const { return (this->data() ? this->data() : NULL); }
+
+  /// Iterator factory
+
+  /// \return A const iterator to the first data element
+  const_iterator cbegin() { return (this->data() ? this->data() : NULL); }
+
+  /// Iterator factory
+
+  /// \return A const iterator to the last data element
+  const_iterator cend() const {
+    return (this->data() ? this->data() + this->size() : NULL);
+  }
+
+  /// Iterator factory
+
+  /// \return A const iterator to the last data element
+  const_iterator cend() {
+    return (this->data() ? this->data() + this->size() : NULL);
+  }
+
   /// Read-only access to the data
 
   /// \return A const pointer to the tensor data

src/TiledArray/tensor/tensor_interface.h

@@ -259,8 +259,8 @@ class TensorInterface {
   /// \param idx The index pack
   template <typename... Index>
   reference operator()(const Index&... idx) {
-    TA_ASSERT(range_.includes(idx...));
-    return data_[range_.ordinal(idx...)];
+    const auto ord = range_.ordinal(idx...);
+    return data_[ord];
   }
 
   /// Element accessor
@@ -269,10 +269,84 @@ class TensorInterface {
   /// \param idx The index pack
   template <typename... Index>
   const_reference operator()(const Index&... idx) const {
-    TA_ASSERT(range_.includes(idx...));
-    return data_[range_.ordinal(idx...)];
+    const auto ord = range_.ordinal(idx...);
+    return data_[ord];
+  }
+
+  /// \brief Tensor interface iterator type
+  ///
+  /// Iterates over elements of a tensor interface whose range is iterable
+  template <typename TI = TensorInterface_>
+  class Iterator : public boost::iterator_facade<
+                       Iterator<TI>,
+                       std::conditional_t<std::is_const_v<TI>,
+                                          const typename TI::value_type,
+                                          typename TI::value_type>,
+                       boost::forward_traversal_tag> {
+   public:
+    using range_iterator = typename TI::range_type::const_iterator;
+
+    Iterator(range_iterator idx_it, TI& ti) : idx_it(idx_it), ti(ti) {}
+
+   private:
+    range_iterator idx_it;
+    TI& ti;
+
+    friend class boost::iterator_core_access;
+
+    /// \brief increments this iterator
+    void increment() { ++idx_it; }
+
+    /// \brief Iterator comparer
+    /// \return true, if \c `*this==*other`
+    bool equal(Iterator const& other) const {
+      return this->idx_it == other.idx_it;
+    }
+
+    /// \brief dereferences this iterator
+    /// \return const reference to the current index
+    auto& dereference() const { return ti(*idx_it); }
+  };
+  friend class Iterator<TensorInterface_>;
+  friend class Iterator<const TensorInterface_>;
+
+  typedef Iterator<TensorInterface_> iterator;              ///< Iterator type
+  typedef Iterator<const TensorInterface_> const_iterator;  ///< Iterator type
+
+  /// Const begin iterator
+
+  /// \return An iterator that points to the beginning of this tensor view
+  const_iterator begin() const {
+    return const_iterator(range().begin(), *this);
+  }
+
+  /// Const end iterator
+
+  /// \return An iterator that points to the end of this tensor view
+  const_iterator end() const { return const_iterator(range().end(), *this); }
+
+  /// Nonconst begin iterator
+
+  /// \return An iterator that points to the beginning of this tensor view
+  iterator begin() { return iterator(range().begin(), *this); }
+
+  /// Nonconst begin iterator
+
+  /// \return An iterator that points to the beginning of this tensor view
+  iterator end() { return iterator(range().end(), *this); }
+
+  /// Const begin iterator
+
+  /// \return An iterator that points to the beginning of this tensor view
+  const_iterator cbegin() const {
+    return const_iterator(range().begin(), *this);
   }
 
+  /// Const end iterator
+
+  /// \return An iterator that points to the end of this tensor view
+  const_iterator cend() const { return const_iterator(range().end(), *this); }
+
   /// Check for empty view
 
   /// \return \c false

src/TiledArray/tile.h

@@ -201,6 +201,26 @@ class Tile {
   /// \return A const iterator to the last data element
   decltype(auto) end() const { return std::end(tensor()); }
 
+  /// Iterator factory
+
+  /// \return A const iterator to the first data element
+  decltype(auto) cbegin() { return std::cbegin(tensor()); }
+
+  /// Iterator factory
+
+  /// \return A const iterator to the first data element
+  decltype(auto) cbegin() const { return std::cbegin(tensor()); }
+
+  /// Iterator factory
+
+  /// \return A const iterator to the last data element
+  decltype(auto) cend() { return std::cend(tensor()); }
+
+  /// Iterator factory
+
+  /// \return A const iterator to the last data element
+  decltype(auto) cend() const { return std::cend(tensor()); }
+
   // Data accessor -------------------------------------------------------
 
   /// Data direct access

tests/btas.cpp

@@ -256,6 +256,27 @@ 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;
+  ta_tensor = make_rand_tile<decltype(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
+  {
+    const auto l = {3, 3, 3};
+    const auto u = r.upbound();
+    BOOST_REQUIRE(r.includes(l));
+    BOOST_REQUIRE_NO_THROW(Tensor(ta_tensor.block(l, u)));
+    Tensor t3(ta_tensor.block(l, u));
+    for (auto i : t3.range()) {
+      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"