dot.hpp

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// Copyright (c) 2024--present, The Simons Foundation
// This file is part of TRIQS/nda and is licensed under the Apache License, Version 2.0.
// SPDX-License-Identifier: Apache-2.0
// See LICENSE in the root of this distribution for details.

 
#pragma once
 
#include "./interface/cutensor_interface.hpp"
#include "./interface/tblis_interface.hpp"
#include "./tools.hpp"
#include "../algorithms.hpp"
#include "../basic_array.hpp"
#include "../declarations.hpp"
#include "../layout/policies.hpp"
#include "../mem/address_space.hpp"
#include "../mem/policies.hpp"
#include "../traits.hpp"
 
#include <string_view>
 
namespace nda::tensor {


  template <BlasArrayOrConj A, BlasArrayOrConjFor<A> B>
  get_value_t<A> dot(A const &a, std::string_view idx_a, B const &b, std::string_view idx_b) {
    // compile-time checks
    constexpr bool run_on_device = mem::have_device_compatible_addr_space<A, B>;
    static_assert(!run_on_device || have_cutensor, "nda::tensor::dot: cuTENSOR support is required");
    static_assert(run_on_device || have_tblis || get_rank<A> == get_rank<B>, "nda::tensor::dot: nda host fallback requires identical ranks");
 
    // dispatch to backends
    if constexpr (run_on_device) {
      auto z = basic_array<get_value_t<A>, 1, C_layout, 'A', heap<mem::common_addr_space<A, B>>>::zeros({1});
      device::contract(get_value_t<A>{1}, a, idx_a, b, idx_b, get_value_t<A>{0}, z.data(), "", z.data());
      return nda::to_host(z)(0);
    } else if constexpr (have_tblis) {
      return tblis::dot(a, idx_a, b, idx_b);
    } else {
      require_equal_indices(idx_a, idx_b, get_rank<A>, "dot");
      return nda::sum(nda::hadamard(a, b));
    }
  }

  template <BlasArrayOrConj A, BlasArrayOrConjFor<A, get_rank<A>> B>
  get_value_t<A> dot(A const &a, B const &b) {
    auto idx = default_index<get_rank<A>>();
    return dot(a, idx, b, idx);
  }

 
} // namespace nda::tensor