inst_layout.h

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/*
 * Copyright 2025 Stanford University, NVIDIA Corporation
 * SPDX-License-Identifier: Apache-2.0
 *
 * 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.
 */
 
// Layout descriptors for Realm RegionInstances
 
#ifndef REALM_INST_LAYOUT_H
#define REALM_INST_LAYOUT_H
 
#include "realm/indexspace.h"
#include "realm/serialize.h"
 
#if defined(REALM_USE_KOKKOS)
// we don't want to include Kokkos_View.hpp because it brings in too much
//  other stuff, so forward declare the pieces we need to define a templated
//  conversion from Realm accessor to Kokkos::View (anything that actually
//  instantiates the template will presumably have included Kokkos_View.hpp
//  in its full glory)
namespace Kokkos {
  template <class, class...>
  class View;
  template <unsigned>
  struct MemoryTraits;
  struct LayoutStride;
  namespace Experimental {
    template <class, class...>
    class OffsetView;
  };
}; // namespace Kokkos
// Kokkos::Unmanaged is an enum, which we can't forward declare - we'll test
//  that we have the right value in the template though
enum
{
  Kokkos_Unmanaged = 0x01
};
 
#define REALM_PROVIDE_ACCESSOR_TO_KOKKOS_VIEW_CONVERSION
#endif
 
#include <vector>
#include <map>
#include <iostream>
 
namespace Realm {
 
  class REALM_PUBLIC_API InstanceLayoutConstraints {
  public:
    InstanceLayoutConstraints(void) {}
    InstanceLayoutConstraints(const std::map<FieldID, size_t> &field_sizes,
                              size_t block_size);
    InstanceLayoutConstraints(const std::vector<size_t> &field_sizes, size_t block_size);
    InstanceLayoutConstraints(const std::vector<FieldID> &field_ids,
                              const std::vector<size_t> &field_sizes, size_t block_size);
    InstanceLayoutConstraints(const FieldID *field_ids, const size_t *field_sizes,
                              size_t num_fields, size_t block_size);
 
    struct FieldInfo {
      FieldID field_id;
      bool fixed_offset;
      size_t offset; // used if `fixed_offset` is true
      size_t size;
      size_t alignment;
    };
    typedef std::vector<FieldInfo> FieldGroup;
 
    std::vector<FieldGroup> field_groups;
  };
 
  namespace PieceLookup {
 
    class CompiledProgram {
    public:
      virtual ~CompiledProgram() {}
 
      // used during compilation to request memory to store instructions
      //  in - can only be used once
      virtual void *allocate_memory(size_t bytes) = 0;
 
      // after any changes to the contents of the memory, this must be
      //  called to ensure all devices see the changes
      virtual void commit_updates() = 0;
 
      struct PerField {
        const PieceLookup::Instruction *start_inst;
        unsigned inst_usage_mask;
        uintptr_t field_offset;
      };
 
      std::map<FieldID, PerField> fields;
      atomic<bool> is_compiled{false};
    };
 
    // this is a namespace instead of an enum so that it can be extended elsewhere
    namespace Opcodes {
      typedef unsigned char Opcode;
 
      static const Opcode OP_INVALID = 0;
      static const Opcode OP_SPLIT1 = 1; // this is a SplitPlane<N,T>
    }                                    // namespace Opcodes
 
    // some processors are limited in which instruction types they can
    //  support, so we build masks to describe usage/capabilities
    static const unsigned ALLOW_SPLIT1 = 1U << Opcodes::OP_SPLIT1;
 
    struct REALM_INTERNAL_API_EXTERNAL_LINKAGE Instruction {
      // all instructions are at least 4 bytes and aligned to 16 bytes, but
      //  the only data common to all is the opcode, which appears in the low
      //  8 bits
      REALM_ALIGNED_TYPE_CONST(uint32_aligned_16, uint32_t, 16);
      uint32_aligned_16 data;
 
      Instruction(uint32_t _data);
 
      REALM_CUDA_HD
      Opcodes::Opcode opcode() const;
 
      // two helper methods that get you to another instruction
 
      // skip() gets the next instruction in sequence, which requires knowing
      //  the size of the current instruction - instructions below take care
      //  of this in most cases
      REALM_CUDA_HD
      const Instruction *skip(size_t bytes) const;
 
      // jump(N) jumps forward in the instruction stream by N 16-B chunks
      //   special case: a delta of 0 is "end of program" and returns null
      REALM_CUDA_HD
      const Instruction *jump(unsigned delta) const;
    };
 
  }; // namespace PieceLookup
 
  class REALM_PUBLIC_API InstanceLayoutGeneric {
  protected:
    // cannot be created directly
    InstanceLayoutGeneric(void);
 
  public:
    template <typename S>
    static InstanceLayoutGeneric *deserialize_new(S &deserializer);
 
    virtual ~InstanceLayoutGeneric(void);
 
    virtual InstanceLayoutGeneric *clone(void) const = 0;
 
    virtual void relocate(size_t adjust_amt) = 0;
 
    virtual void print(std::ostream &os) const = 0;
 
    template <int N, typename T>
    static InstanceLayoutGeneric *
    choose_instance_layout(IndexSpace<N, T> is, const InstanceLayoutConstraints &ilc,
                           const int dim_order[N]);
 
    template <int N, typename T>
    static InstanceLayoutGeneric *
    choose_instance_layout(IndexSpace<N, T> is, const std::vector<Rect<N, T>> &covering,
                           const InstanceLayoutConstraints &ilc, const int dim_order[N]);
 
    REALM_INTERNAL_API_EXTERNAL_LINKAGE
    virtual void compile_lookup_program(PieceLookup::CompiledProgram &p) const = 0;
 
    size_t bytes_used;
    size_t alignment_reqd;
 
    // we optimize for fields being laid out similarly, and have fields
    //  indirectly reference a piece list
    struct FieldLayout {
      int list_idx;
      size_t rel_offset;
      int size_in_bytes;
    };
 
    using FieldMap = std::map<FieldID, FieldLayout>;
    FieldMap fields;
    bool idindexed_fields{false};
  };
 
  REALM_PUBLIC_API
  std::ostream &operator<<(std::ostream &os, const InstanceLayoutGeneric &ilg);
 
  class REALM_PUBLIC_API InstanceLayoutOpaque : public InstanceLayoutGeneric {
  public:
    InstanceLayoutOpaque(size_t _bytes_used, size_t _alignment_reqd);
 
    virtual InstanceLayoutGeneric *clone(void) const;
 
    virtual void relocate(size_t adjust_amt);
 
    virtual void print(std::ostream &os) const;
 
    REALM_INTERNAL_API_EXTERNAL_LINKAGE
    virtual void compile_lookup_program(PieceLookup::CompiledProgram &p) const;
  };
 
  namespace PieceLayoutTypes {
    typedef unsigned char LayoutType;
 
    static const LayoutType InvalidLayoutType = 0;
    static const LayoutType AffineLayoutType = 1;
  }; // namespace PieceLayoutTypes
 
  class REALM_PUBLIC_API InstanceLayoutPieceBase {
  public:
    InstanceLayoutPieceBase(PieceLayoutTypes::LayoutType _layout_type);
 
    virtual ~InstanceLayoutPieceBase(void);
 
    virtual void relocate(size_t base_offset) = 0;
 
    virtual void print(std::ostream &os) const = 0;
 
    // used for constructing lookup programs
    virtual size_t lookup_inst_size() const = 0;
    virtual PieceLookup::Instruction *create_lookup_inst(void *ptr,
                                                         unsigned next_delta) const = 0;
 
    PieceLayoutTypes::LayoutType layout_type;
  };
 
  template <int N, typename T = int>
  class REALM_PUBLIC_API InstanceLayoutPiece : public InstanceLayoutPieceBase {
  public:
    InstanceLayoutPiece(void);
    InstanceLayoutPiece(PieceLayoutTypes::LayoutType _layout_type);
    InstanceLayoutPiece(PieceLayoutTypes::LayoutType _layout_type,
                        const Rect<N, T> &_bounds);
 
    template <typename S>
    static InstanceLayoutPiece<N, T> *deserialize_new(S &deserializer);
 
    virtual InstanceLayoutPiece<N, T> *clone(void) const = 0;
 
    virtual size_t calculate_offset(const Point<N, T> &p) const = 0;
 
    Rect<N, T> bounds;
  };
 
  template <int N, typename T>
  REALM_PUBLIC_API std::ostream &operator<<(std::ostream &os,
                                            const InstanceLayoutPiece<N, T> &ilp);
 
  template <int N, typename T = int>
  class REALM_PUBLIC_API AffineLayoutPiece : public InstanceLayoutPiece<N, T> {
  public:
    AffineLayoutPiece(void);
 
    template <typename S>
    static InstanceLayoutPiece<N, T> *deserialize_new(S &deserializer);
 
    virtual InstanceLayoutPiece<N, T> *clone(void) const;
 
    virtual size_t calculate_offset(const Point<N, T> &p) const;
 
    virtual void relocate(size_t base_offset);
 
    virtual void print(std::ostream &os) const;
 
    // used for constructing lookup programs
    virtual size_t lookup_inst_size() const;
    virtual PieceLookup::Instruction *create_lookup_inst(void *ptr,
                                                         unsigned next_delta) const;
 
    static Serialization::PolymorphicSerdezSubclass<InstanceLayoutPiece<N, T>,
                                                    AffineLayoutPiece<N, T>>
        serdez_subclass;
 
    template <typename S>
    bool serialize(S &serializer) const;
 
    Point<N, size_t> strides;
    size_t offset;
  };
 
  template <int N, typename T = int>
  class REALM_PUBLIC_API InstancePieceList {
  public:
    InstancePieceList(void);
    ~InstancePieceList(void);
 
    InstancePieceList(const InstancePieceList &) = default;
    InstancePieceList &operator=(const InstancePieceList &) = default;
    InstancePieceList(InstancePieceList &&) noexcept = default;
    InstancePieceList &operator=(InstancePieceList &&) noexcept = default;
 
    const InstanceLayoutPiece<N, T> *find_piece(Point<N, T> p) const;
 
    void relocate(size_t base_offset);
 
    template <typename S>
    bool serialize(S &serializer) const;
    template <typename S>
    bool deserialize(S &deserializer);
 
    std::vector<InstanceLayoutPiece<N, T> *> pieces;
    // placeholder for lookup structure (e.g. K-D tree)
  };
 
  template <int N, typename T>
  REALM_PUBLIC_API std::ostream &operator<<(std::ostream &os,
                                            const InstancePieceList<N, T> &ipl);
 
  template <int N, typename T = int>
  class REALM_PUBLIC_API InstanceLayout : public InstanceLayoutGeneric {
  public:
    InstanceLayout(void);
 
    template <typename S>
    static InstanceLayoutGeneric *deserialize_new(S &deserializer);
 
    virtual ~InstanceLayout(void);
 
    virtual InstanceLayoutGeneric *clone(void) const;
 
    virtual void relocate(size_t base_offset);
 
    virtual void print(std::ostream &os) const;
 
    REALM_INTERNAL_API_EXTERNAL_LINKAGE
    virtual void compile_lookup_program(PieceLookup::CompiledProgram &p) const;
 
    size_t calculate_offset(Point<N, T> p, FieldID fid) const;
 
    IndexSpace<N, T> space;
    std::vector<InstancePieceList<N, T>> piece_lists;
 
    // Pre-computed dimension ordering for idindexed_fields
    std::vector<int> preferred_dim_order;
 
    static Serialization::PolymorphicSerdezSubclass<InstanceLayoutGeneric,
                                                    InstanceLayout<N, T>>
        serdez_subclass;
 
    template <typename S>
    bool serialize(S &serializer) const;
  };
 
  // instance layouts are compiled into "piece lookup programs" for fast
  //  access on both CPU and accelerators
 
  namespace PieceLookup {
 
    namespace Opcodes {
      static const Opcode OP_AFFINE_PIECE = 2; // this is a AffinePiece<N,T>
    }
 
    static const unsigned ALLOW_AFFINE_PIECE = 1U << Opcodes::OP_AFFINE_PIECE;
 
    template <int N, typename T>
    struct REALM_INTERNAL_API_EXTERNAL_LINKAGE AffinePiece : public Instruction {
      // data is: { delta[23:0], opcode[7:0] }
      // top 24 bits of data is jump delta
      AffinePiece(unsigned next_delta);
 
      REALM_CUDA_HD
      unsigned delta() const;
 
      Rect<N, T> bounds;
      uintptr_t base;
      Point<N, size_t> strides;
 
      REALM_CUDA_HD
      const Instruction *next() const;
    };
 
    template <int N, typename T>
    struct REALM_INTERNAL_API_EXTERNAL_LINKAGE SplitPlane : public Instruction {
      // data is: { delta[15:0], dim[7:0], opcode[7:0] }
      SplitPlane(int _split_dim, T _split_plane, unsigned _next_delta);
 
      void set_delta(unsigned _next_delta);
 
      REALM_CUDA_HD
      unsigned delta() const;
      REALM_CUDA_HD
      int split_dim() const;
 
      // if point's coord is less than split_plane, go to next, else jump
      T split_plane;
 
      REALM_CUDA_HD
      const Instruction *next(const Point<N, T> &p) const;
 
      REALM_CUDA_HD
      bool splits_rect(const Rect<N, T> &r) const;
    };
 
  }; // namespace PieceLookup
 
  template <typename FT>
  class REALM_INTERNAL_API_EXTERNAL_LINKAGE AccessorRefHelper {
  public:
    AccessorRefHelper(RegionInstance _inst, size_t _offset);
 
    // "read"
    operator FT(void) const;
 
    // "write"
    AccessorRefHelper(const AccessorRefHelper &) = default;
    AccessorRefHelper(AccessorRefHelper &&) noexcept = default;
    AccessorRefHelper<FT> &operator=(const FT &newval);
    AccessorRefHelper<FT> &operator=(const AccessorRefHelper<FT> &rhs);
 
  protected:
    template <typename T>
    friend std::ostream &operator<<(std::ostream &os, const AccessorRefHelper<T> &arh);
 
    RegionInstance inst;
    size_t offset;
  };
 
  template <typename FT, int N, typename T = int>
  class REALM_PUBLIC_API GenericAccessor {
  public:
    GenericAccessor(void);
 
    GenericAccessor(RegionInstance inst, FieldID field_id, size_t subfield_offset = 0);
 
    GenericAccessor(RegionInstance inst, FieldID field_id, const Rect<N, T> &subrect,
                    size_t subfield_offset = 0);
 
    ~GenericAccessor(void);
 
    static bool is_compatible(RegionInstance inst, size_t field_offset);
    static bool is_compatible(RegionInstance inst, size_t field_offset,
                              const Rect<N, T> &subrect);
 
    template <typename INST>
    static bool is_compatible(const INST &instance, unsigned field_id);
    template <typename INST>
    static bool is_compatible(const INST &instance, unsigned field_id,
                              const Rect<N, T> &subrect);
 
    // GenericAccessor does not support returning a pointer to an element
    // FT *ptr(const Point<N,T>& p) const;
 
    FT read(const Point<N, T> &p);
    void write(const Point<N, T> &p, FT newval);
 
    AccessorRefHelper<FT> operator[](const Point<N, T> &p);
 
    // instead of storing the top-level layout - we narrow down to just the
    //  piece list and relative offset of the field we're interested in
    RegionInstance inst;
    const InstancePieceList<N, T> *piece_list;
    size_t rel_offset;
    // cache the most recently-used piece
    const InstanceLayoutPiece<N, T> *prev_piece;
 
    // protected:
    //  not a const method because of the piece caching
    size_t get_offset(const Point<N, T> &p);
  };
 
  template <typename FT, int N, typename T>
  REALM_PUBLIC_API std::ostream &operator<<(std::ostream &os,
                                            const GenericAccessor<FT, N, T> &a);
 
  template <typename FT, int N, typename T = int>
  class REALM_PUBLIC_API AffineAccessor {
  public:
    // NOTE: even when compiling with nvcc, non-default constructors are only
    //  available in host code
 
    // TODO: Sean check if this is safe for a default constructor
    REALM_CUDA_HD
    AffineAccessor(void);
 
    AffineAccessor(RegionInstance inst, FieldID field_id, size_t subfield_offset = 0);
 
    AffineAccessor(RegionInstance inst, FieldID field_id, const Rect<N, T> &subrect,
                   size_t subfield_offset = 0);
 
 
    template <int N2, typename T2>
    AffineAccessor(RegionInstance inst, const Matrix<N2, N, T2> &transform,
                   const Point<N2, T2> &offset, FieldID field_id,
                   size_t subfield_offset = 0);
 
    // note that the subrect here is in in the accessor's indexspace
    //  (from which the corresponding subrectangle in the instance can be
    //  easily determined)
    template <int N2, typename T2>
    AffineAccessor(RegionInstance inst, const Matrix<N2, N, T2> &transform,
                   const Point<N2, T2> &offset, FieldID field_id,
                   const Rect<N, T> &subrect, size_t subfield_offset = 0);
 
    REALM_CUDA_HD
    ~AffineAccessor(void);
 
    AffineAccessor(const AffineAccessor &) = default;
    AffineAccessor &operator=(const AffineAccessor &) = default;
    AffineAccessor(AffineAccessor &&) noexcept = default;
    AffineAccessor &operator=(AffineAccessor &&) noexcept = default;
 
    static bool is_compatible(RegionInstance inst, FieldID field_id);
    static bool is_compatible(RegionInstance inst, FieldID field_id,
                              const Rect<N, T> &subrect);
    template <int N2, typename T2>
    static bool is_compatible(RegionInstance inst, const Matrix<N2, N, T2> &transform,
                              const Point<N2, T2> &offset, FieldID field_id);
    template <int N2, typename T2>
    static bool is_compatible(RegionInstance inst, const Matrix<N2, N, T2> &transform,
                              const Point<N2, T2> &offset, FieldID field_id,
                              const Rect<N, T> &subrect);
 
    // used by constructors or can be called directly
    REALM_CUDA_HD
    void reset();
    void reset(RegionInstance inst, FieldID field_id, size_t subfield_offset = 0);
    void reset(RegionInstance inst, FieldID field_id, const Rect<N, T> &subrect,
               size_t subfield_offset = 0);
    template <int N2, typename T2>
    void reset(RegionInstance inst, const Matrix<N2, N, T2> &transform,
               const Point<N2, T2> &offset, FieldID field_id, size_t subfield_offset = 0);
    template <int N2, typename T2>
    void reset(RegionInstance inst, const Matrix<N2, N, T2> &transform,
               const Point<N2, T2> &offset, FieldID field_id, const Rect<N, T> &subrect,
               size_t subfield_offset = 0);
 
    REALM_CUDA_HD
    FT *ptr(const Point<N, T> &p) const;
    REALM_CUDA_HD
    FT read(const Point<N, T> &p) const;
    REALM_CUDA_HD
    void write(const Point<N, T> &p, FT newval) const;
 
    REALM_CUDA_HD
    FT &operator[](const Point<N, T> &p) const;
 
    REALM_CUDA_HD
    bool is_dense_arbitrary(const Rect<N, T> &bounds) const; // any dimension ordering
    REALM_CUDA_HD
    bool is_dense_col_major(const Rect<N, T> &bounds) const; // Fortran dimension ordering
    REALM_CUDA_HD
    bool is_dense_row_major(const Rect<N, T> &bounds) const; // C dimension ordering
 
#ifdef REALM_PROVIDE_ACCESSOR_TO_KOKKOS_VIEW_CONVERSION
    // conversion to Kokkos unmanaged views
 
    // Kokkos::View uses relative ("local") indexing - the first element is
    //  always index 0, even when accessing a subregion that does not include
    //  global element 0
    template <typename... Args>
    operator Kokkos::View<Args...>() const;
 
    // Kokkos::Experimental::OffsetView uses absolute ("global") indexing -
    //  the indices used on the OffsetView::operator() match what is used for
    //  the AffineAccessor's operator[]
    template <typename... Args>
    operator Kokkos::Experimental::OffsetView<Args...>() const;
#endif
 
    // protected:
    // friend
    //  std::ostream& operator<<(std::ostream& os, const AffineAccessor<FT,N,T>& a);
// #define REALM_ACCESSOR_DEBUG
#if defined(REALM_ACCESSOR_DEBUG) || defined(REALM_USE_KOKKOS)
    Rect<N, T> bounds;
#endif
#ifdef REALM_USE_KOKKOS
    bool bounds_specified;
#endif
#ifdef REALM_ACCESSOR_DEBUG
    RegionInstance dbg_inst;
#if defined(__CUDACC__) || defined(__HIPCC__)
#error "REALM_ACCESSOR_DEBUG macro for AffineAccessor not supported for GPU code"
#endif
#endif
    uintptr_t base;
    Point<N, size_t> strides;
 
  protected:
    REALM_CUDA_HD
    FT *get_ptr(const Point<N, T> &p) const;
  };
 
  template <typename FT, int N, typename T>
  REALM_PUBLIC_API std::ostream &operator<<(std::ostream &os,
                                            const AffineAccessor<FT, N, T> &a);
 
  // a multi-affine accessor handles instances with multiple pieces, but only
  //  if all of them are affine
  template <typename FT, int N, typename T = int>
  class MultiAffineAccessor;
 
  template <typename FT, int N, typename T>
  REALM_PUBLIC_API std::ostream &operator<<(std::ostream &os,
                                            const MultiAffineAccessor<FT, N, T> &a);
 
  template <typename FT, int N, typename T>
  class REALM_PUBLIC_API MultiAffineAccessor {
  public:
    REALM_CUDA_HD
    MultiAffineAccessor(void);
 
    MultiAffineAccessor(RegionInstance inst, FieldID field_id,
                        size_t subfield_offset = 0);
 
    MultiAffineAccessor(RegionInstance inst, FieldID field_id, const Rect<N, T> &subrect,
                        size_t subfield_offset = 0);
 
    REALM_CUDA_HD
    ~MultiAffineAccessor(void);
 
    MultiAffineAccessor(const MultiAffineAccessor &) = default;
    MultiAffineAccessor &operator=(const MultiAffineAccessor &) = default;
    MultiAffineAccessor(MultiAffineAccessor &&) noexcept = default;
    MultiAffineAccessor &operator=(MultiAffineAccessor &&) noexcept = default;
 
    static bool is_compatible(RegionInstance inst, FieldID field_id);
    static bool is_compatible(RegionInstance inst, FieldID field_id,
                              const Rect<N, T> &subrect);
 
    // used by constructors or can be called directly
    REALM_CUDA_HD
    void reset();
    void reset(RegionInstance inst, FieldID field_id, size_t subfield_offset = 0);
    void reset(RegionInstance inst, FieldID field_id, const Rect<N, T> &subrect,
               size_t subfield_offset = 0);
 
 
    REALM_CUDA_HD
    FT *ptr(const Point<N, T> &p) const;
    REALM_CUDA_HD
    FT *ptr(const Rect<N, T> &r, size_t strides[N]) const;
    REALM_CUDA_HD
    FT read(const Point<N, T> &p) const;
    REALM_CUDA_HD
    void write(const Point<N, T> &p, FT newval) const;
 
    REALM_CUDA_HD
    FT &operator[](const Point<N, T> &p) const;
 
    REALM_CUDA_HD
    FT *ptr(const Point<N, T> &p);
    REALM_CUDA_HD
    FT *ptr(const Rect<N, T> &r, size_t strides[N]);
    REALM_CUDA_HD
    FT read(const Point<N, T> &p);
    REALM_CUDA_HD
    void write(const Point<N, T> &p, FT newval);
 
    REALM_CUDA_HD
    FT &operator[](const Point<N, T> &p);
 
  protected:
    friend std::ostream &operator<< <FT, N, T>(std::ostream &os,
                                               const MultiAffineAccessor<FT, N, T> &a);
 
    // cached info from the most recent piece, or authoritative info for
    //  a single piece
    bool piece_valid;
    Rect<N, T> piece_bounds;
    uintptr_t piece_base;
    Point<N, size_t> piece_strides;
    // if we need to do a new lookup, this is where we start
    const PieceLookup::Instruction *start_inst;
    size_t field_offset;
  };
 
}; // namespace Realm
 
#include "realm/inst_layout.inl"
 
#endif // ifndef REALM_INST_LAYOUT_H