// Copyright 2018 Google LLC

//

// 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.

#include "cc/random.h"

#include "absl/time/clock.h"

#include "absl/time/time.h"

namespace minigo {

namespace {

uint64_t ChooseSeed(uint64_t seed) {

return seed != 0 ? seed : absl::ToUnixMicros(absl::Now());

}

} // namespace

Random::Random(uint64_t seed) : seed_(ChooseSeed(seed)), impl_(seed_) {}

void Random::Dirichlet(float alpha, absl::Span<float> samples) {

std::gamma_distribution<float> distribution(alpha);

float sum = 0;

for (float& sample : samples) {

sample = distribution(impl_);

sum += sample;

}

float norm = 1 / sum;

for (float& sample : samples) {

sample *= norm;

}

}

void Random::Uniform(float mn, float mx, absl::Span<float> samples) {

std::uniform_real_distribution<float> distribution(mn, mx);

for (float& sample : samples) {

sample = distribution(impl_);

}

}

} // namespace minigo