/*!
 *  Copyright (c) 2017 by Contributors
 * \file random.cc
 * \brief Random number generator interfaces
 */

#include <dmlc/omp.h>
#include <dgl/runtime/registry.h>
#include <dgl/runtime/packed_func.h>
#include <dgl/runtime/parallel_for.h>
#include <dgl/random.h>
#include <dgl/array.h>

#ifdef DGL_USE_CUDA
#include "../runtime/cuda/cuda_common.h"
#endif  // DGL_USE_CUDA

using namespace dgl::runtime;

namespace dgl {

DGL_REGISTER_GLOBAL("rng._CAPI_SetSeed")
.set_body([] (DGLArgs args, DGLRetValue *rv) {
    const int seed = args[0];

    runtime::parallel_for(0, omp_get_max_threads(), [&](size_t b, size_t e) {
      for (auto i = b; i < e; ++i) {
        RandomEngine::ThreadLocal()->SetSeed(seed);
      }
    });
#ifdef DGL_USE_CUDA
    if (DeviceAPI::Get(kDGLCUDA)->IsAvailable()) {
      auto* thr_entry = CUDAThreadEntry::ThreadLocal();
      if (!thr_entry->curand_gen) {
        CURAND_CALL(curandCreateGenerator(&thr_entry->curand_gen, CURAND_RNG_PSEUDO_DEFAULT));
      }
      CURAND_CALL(curandSetPseudoRandomGeneratorSeed(
          thr_entry->curand_gen,
          static_cast<uint64_t>(seed)));
    }
#endif  // DGL_USE_CUDA
  });

DGL_REGISTER_GLOBAL("rng._CAPI_Choice")
.set_body([] (DGLArgs args, DGLRetValue *rv) {
    const int64_t num = args[0];
    const int64_t population = args[1];
    const NDArray prob = args[2];
    const bool replace = args[3];
    const int bits = args[4];
    CHECK(bits == 32 || bits == 64)
      << "Supported bit widths are 32 and 64, but got " << bits << ".";
    if (aten::IsNullArray(prob)) {
      if (bits == 32) {
        *rv = RandomEngine::ThreadLocal()->UniformChoice<int32_t>(num, population, replace);
      } else {
        *rv = RandomEngine::ThreadLocal()->UniformChoice<int64_t>(num, population, replace);
      }
    } else {
      if (bits == 32) {
        ATEN_FLOAT_TYPE_SWITCH(prob->dtype, FloatType, "probability", {
          *rv = RandomEngine::ThreadLocal()->Choice<int32_t, FloatType>(num, prob, replace);
        });
      } else {
        ATEN_FLOAT_TYPE_SWITCH(prob->dtype, FloatType, "probability", {
          *rv = RandomEngine::ThreadLocal()->Choice<int64_t, FloatType>(num, prob, replace);
        });
      }
    }
  });

};  // namespace dgl
