flash-attention/csrc/cutlass/include/cute/tensor_predicate.hpp

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#pragma once

#include <cute/config.hpp>

#include <cute/numeric/integral_constant.hpp>

namespace cute
{

template <class T>
struct ConstantTensor
{
  template <class... Coords>
  CUTE_HOST_DEVICE constexpr
  T const&
  operator()(Coords const&...) const {
    return val_;
  }

  T val_;
};

struct TrivialPredTensor
{
  template <class... Coords>
  CUTE_HOST_DEVICE constexpr
  true_type
  operator()(Coords const&...) const {
    return {};
  }
};

template <class Fn>
struct FunctionPredTensor
{
  CUTE_HOST_DEVICE constexpr
  FunctionPredTensor(Fn const& fn) : fn_(fn) {}

  template <class... Coords>
  CUTE_HOST_DEVICE constexpr
  auto
  operator()(Coords const&... coords) const {
    return fn_(coords...);
  }

  Fn const& fn_;
};

} // end namespace cute