values.h

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/* Copyright 2026 Stanford University, NVIDIA Corporation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
#ifndef __LEGION_DEFERRED_VALUES_H__
#define __LEGION_DEFERRED_VALUES_H__
 
#include "legion/api/types.h"
#include "legion/api/geometry.h"
 
namespace Legion {
 
  struct DeferredValueRequest {
  public:
    DeferredValueRequest(void) = default;
    // Convenience constructors
    DeferredValueRequest(
        Memory mem, size_t size, size_t align = alignof(std::max_align_t),
        const void* initial = nullptr, bool escaping = true);
    DeferredValueRequest(
        Memory::Kind kind, size_t size,
        size_t align = alignof(std::max_align_t), const void* initial = nullptr,
        bool escaping = true);
  public:
    size_t field_size = 0;
    size_t alignment = alignof(std::max_align_t);
    const void* initial_value = nullptr;
    union {
      Memory exact = Memory::NO_MEMORY;
      Memory::Kind kind;
    } memory;
    bool is_exact = true;
    bool can_fail = false;
    bool escaping = true;
  };
 
  class UntypedDeferredValue {
  public:
    UntypedDeferredValue(void);
    UntypedDeferredValue(
        size_t field_size, Memory target_memory,
        const void* initial_value = nullptr, size_t alignment = 16,
        bool escaping = true);
    UntypedDeferredValue(
        size_t field_size, Memory::Kind memory_kind = Memory::Z_COPY_MEM,
        const void* initial_value = nullptr, size_t alignment = 16,
        bool escaping = true);
    UntypedDeferredValue(const UntypedDeferredValue& rhs);
  public:
    template<typename T>
    inline operator DeferredValue<T>(void) const;
    template<typename REDOP, bool EXCLUSIVE>
    inline operator DeferredReduction<REDOP, EXCLUSIVE>(void) const;
    inline size_t field_size(void) const;
  public:
    inline bool exists(void) const { return instance.exists(); }
    void finalize(Context ctx) const;
    Realm::RegionInstance get_instance(void) const;
    static void report_incompatible_accessor(
        const char* accessor_kind, bool buffer = false);
  protected:
    Realm::RegionInstance instance;
  protected:
    static Domain get_index_space_bounds(IndexSpace space);
    friend class Runtime;
    template<PrivilegeMode, typename, int, typename, typename, bool>
    friend class FieldAccessor;
    template<typename, bool, int, typename, typename, bool>
    friend class ReductionAccessor;
  };
 
  template<typename T>
  class DeferredValue : public UntypedDeferredValue {
  public:
    DeferredValue(
        T initial_value, size_t alignment = std::alignment_of<T>(),
        Memory::Kind memory_kind = Memory::Z_COPY_MEM, bool escaping = true);
    DeferredValue(
        T initial_value, Memory target_memory,
        size_t alignment = std::alignment_of<T>(), bool escaping = true);
  public:
    __LEGION_CUDA_HD__
    inline T read(void) const;
    __LEGION_CUDA_HD__
    inline void write(T value) const;
    __LEGION_CUDA_HD__
    inline T* ptr(void) const;
    __LEGION_CUDA_HD__
    inline T& ref(void) const;
    __LEGION_CUDA_HD__
    inline operator T(void) const;
    __LEGION_CUDA_HD__
    inline DeferredValue<T>& operator=(T value);
  public:
    typedef T value_type;
    typedef T& reference;
    typedef const T& const_reference;
  protected:
    friend class UntypedDeferredValue;
    DeferredValue(void);
    Realm::AffineAccessor<T, 1, coord_t> accessor;
  };
 
  template<typename REDOP, bool EXCLUSIVE = false>
  class DeferredReduction : public DeferredValue<typename REDOP::RHS> {
  public:
    DeferredReduction(
        size_t alignment = std::alignment_of<typename REDOP::RHS>(),
        bool escaping = true);
  public:
    __LEGION_CUDA_HD__
    inline void reduce(typename REDOP::RHS val) const;
    __LEGION_CUDA_HD__
    inline void operator<<=(typename REDOP::RHS val) const;
  public:
    typedef typename REDOP::RHS value_type;
    typedef typename REDOP::RHS& reference;
    typedef const typename REDOP::RHS& const_reference;
  };
 
}  // namespace Legion
 
#include "legion/api/values.inl"
 
#endif  // __LEGION_DEFERRED_VALUES_H__