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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
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#ifndef IMPALA_TESTUTIL_RAND_UTIL_H_
#define IMPALA_TESTUTIL_RAND_UTIL_H_

#include <cstdint>
#include <cstdlib>
#include <random>

#include "common/logging.h"

namespace impala {

/// Test helpers for randomised tests.
class RandTestUtil {
 public:
  /// Seed 'rng' with a seed either from the environment variable 'env_var' or the
  /// random device of the platform.
  template <typename RandomEngine>
  static void SeedRng(const char* env_var, RandomEngine* rng) {
    const char* seed_str = getenv(env_var);
    int64_t seed;
    if (seed_str != nullptr) {
      seed = atoi(seed_str);
    } else {
      seed = std::random_device()();
    }
    LOG(INFO) << "Random seed (overridable with " << env_var << "): " << seed;
    rng->seed(seed);
  }

  /// Create 'num_threads' rngs, seeded using 'seed_rng'. Used when we want each thread
  /// to have its own RNG (since they are not thread-safe).
  static vector<std::mt19937> CreateThreadLocalRngs(
      int num_threads, std::mt19937* seed_rng) {
    vector<std::mt19937> rngs(num_threads);
    for (std::mt19937& rng : rngs) rng.seed((*seed_rng)());
    return rngs;
  }
};
}

#endif