DeviceHashmap.h

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// -                        Open3D: www.open3d.org                            -
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// The MIT License (MIT)
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// Copyright (c) 2018 www.open3d.org
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#pragma once

#include "open3d/core/CUDAUtils.h"
#include "open3d/core/MemoryManager.h"
#include "open3d/core/Tensor.h"
#include "open3d/core/hashmap/HashmapBuffer.h"

namespace open3d {
namespace core {

class DefaultHash {
    // Default constructor is required, since we need a struct instead of its
    // pointer as a member in a hash table for CUDA kernel launches.
    // Must set key_size_ before calling operator(), otherwise the behavior will
    // be undefined.
public:
    DefaultHash() {}
    DefaultHash(int64_t key_size) : key_size_in_int_(key_size / sizeof(int)) {
        if (key_size % 4 != 0 || key_size_in_int_ == 0) {
            utility::LogError(
                    "[DefaultHash] Only support keys whose byte size is "
                    "multiples of sizeof(int)");
        }
    }

    uint64_t OPEN3D_HOST_DEVICE operator()(const void* key_ptr) const {
        uint64_t hash = UINT64_C(14695981039346656037);

        auto cast_key_ptr = static_cast<const int*>(key_ptr);
        for (int64_t i = 0; i < key_size_in_int_; ++i) {
            hash ^= cast_key_ptr[i];
            hash *= UINT64_C(1099511628211);
        }
        return hash;
    }

    int64_t key_size_in_int_;
};

class DefaultKeyEq {
    // Default constructor is required, since we need a struct instead of its
    // pointer as a member in a hash table for CUDA kernel launches.
    // Must set key_size_ before calling operator(), otherwise the behavior will
    // be undefined.
public:
    DefaultKeyEq() {}
    DefaultKeyEq(int64_t key_size) : key_size_in_int_(key_size / sizeof(int)) {
        if (key_size % 4 != 0 || key_size_in_int_ == 0) {
            utility::LogError(
                    "[DefaultKeyEq] Only support keys whose byte size is "
                    "multiples of sizeof(int)");
        }
    }

    bool OPEN3D_HOST_DEVICE operator()(const void* lhs, const void* rhs) const {
        if (lhs == nullptr || rhs == nullptr) {
            return false;
        }

        auto lhs_key_ptr = static_cast<const int*>(lhs);
        auto rhs_key_ptr = static_cast<const int*>(rhs);

        bool is_eq = true;
        for (int64_t i = 0; i < key_size_in_int_; ++i) {
            is_eq = is_eq && (lhs_key_ptr[i] == rhs_key_ptr[i]);
        }
        return is_eq;
    }

    int64_t key_size_in_int_;
};

template <typename Hash, typename KeyEq>
class DeviceHashmap {
public:
    DeviceHashmap(int64_t init_buckets,
                  int64_t init_capacity,
                  int64_t dsize_key,
                  int64_t dsize_value,
                  const Device& device)
        : bucket_count_(init_buckets),
          capacity_(init_capacity),
          dsize_key_(dsize_key),
          dsize_value_(dsize_value),
          device_(device) {}
    virtual ~DeviceHashmap() {}

    virtual void Rehash(int64_t buckets) = 0;

    virtual void Insert(const void* input_keys,
                        const void* input_values,
                        addr_t* output_iterators,
                        bool* output_masks,
                        int64_t count) = 0;

    virtual void Activate(const void* input_keys,
                          addr_t* output_iterators,
                          bool* output_masks,
                          int64_t count) = 0;

    virtual void Find(const void* input_keys,
                      addr_t* output_iterators,
                      bool* output_masks,
                      int64_t count) = 0;

    virtual void Erase(const void* input_keys,
                       bool* output_masks,
                       int64_t count) = 0;

    virtual int64_t GetActiveIndices(addr_t* output_indices) = 0;

    virtual int64_t Size() const = 0;

    int64_t GetCapacity() const { return capacity_; }
    int64_t GetBucketCount() const { return bucket_count_; }
    Device GetDevice() const { return device_; }
    int64_t GetKeyBytesize() const { return dsize_key_; }
    int64_t GetValueBytesize() const { return dsize_value_; }

    Tensor& GetKeyBuffer() { return buffer_->GetKeyBuffer(); }
    Tensor& GetValueBuffer() { return buffer_->GetValueBuffer(); }

    virtual std::vector<int64_t> BucketSizes() const = 0;

    virtual float LoadFactor() const = 0;

public:
    int64_t bucket_count_;
    int64_t capacity_;
    int64_t dsize_key_;
    int64_t dsize_value_;

    Device device_;

    std::shared_ptr<HashmapBuffer> buffer_;

    float avg_capacity_bucket_ratio() {
        return float(capacity_) / float(bucket_count_);
    }
};


typedef DeviceHashmap<DefaultHash, DefaultKeyEq> DefaultDeviceHashmap;

std::shared_ptr<DefaultDeviceHashmap> CreateDefaultDeviceHashmap(
        int64_t init_buckets,
        int64_t init_capacity,
        int64_t dsize_key,
        int64_t dsize_value,
        const Device& device);

std::shared_ptr<DefaultDeviceHashmap> CreateDefaultCPUHashmap(
        int64_t init_buckets,
        int64_t init_capacity,
        int64_t dsize_key,
        int64_t dsize_value,
        const Device& device);

std::shared_ptr<DefaultDeviceHashmap> CreateDefaultCUDAHashmap(
        int64_t init_buckets,
        int64_t init_capacity,
        int64_t dsize_key,
        int64_t dsize_value,
        const Device& device);

}  // namespace core
}  // namespace open3d