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[thin] Adopt stateful random number generators

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This commit is contained in:
Ming-Hung Tsai
2020-08-04 11:45:36 +08:00
parent 06dfb976c2
commit 3f19818c56
3 changed files with 39 additions and 9 deletions
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25
base/sequence_generator.cc
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@@ -1,5 +1,7 @@
#include "base/run_set.h"
#include "base/sequence_generator.h"
#include <chrono>
#include <random>
#include <stdexcept>
//----------------------------------------------------------------
@@ -80,6 +82,9 @@ namespace {
: begin_(begin),
step_(step),
max_forward_steps_(seq_nr),
rand_seed_(std::chrono::high_resolution_clock::now().time_since_epoch().count()),
results_engine_(rand_seed_),
steps_engine_(rand_seed_),
nr_generated_(0)
{
if (!size || !step || !seq_nr)
@@ -93,8 +98,14 @@ namespace {
if (!max_forward_steps_ || max_forward_steps_ > nr_steps_)
throw std::runtime_error("invalid number of forward steps");
if (max_forward_steps_ > 1)
results_distr_ = std::uniform_int_distribution<uint64_t>(0,
nr_steps_ - 1);
if (max_forward_steps_ > 1) {
steps_distr_ = std::uniform_int_distribution<uint64_t>(1,
max_forward_steps_);
reset_forward_generator();
}
}
uint64_t next() {
@@ -109,7 +120,7 @@ namespace {
void reset_forward_generator() {
uint64_t begin = peek_random_step();
unsigned seq_nr = (std::rand() % max_forward_steps_) + 1;
unsigned seq_nr = steps_distr_(steps_engine_);
base::run_set<uint64_t>::const_iterator it = rand_map_.upper_bound(begin);
if (it != rand_map_.end())
seq_nr = std::min<uint64_t>(seq_nr, *it->begin_ - begin);
@@ -148,12 +159,13 @@ namespace {
}
}
uint64_t peek_random_step() const {
// TODO: improve the complexity of generating unique sequence
uint64_t peek_random_step() {
uint64_t step_idx;
bool found = true;
while (found) {
step_idx = std::rand() % nr_steps_;
step_idx = results_distr_(results_engine_);
found = rand_map_.member(step_idx);
}
@@ -164,7 +176,12 @@ namespace {
uint64_t nr_steps_;
uint64_t step_;
unsigned max_forward_steps_;
uint64_t rand_seed_;
std::mt19937_64 results_engine_;
std::mt19937_64 steps_engine_;
std::uniform_int_distribution<uint64_t> results_distr_;
std::uniform_int_distribution<uint64_t> steps_distr_;
base::run_set<uint64_t> rand_map_;
uint64_t nr_generated_;
forward_sequence_generator forward_gen_;