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c++randomstateofstream

Writing and Reading a random number state to file

I am trying to save the state of a random number generator as follows:

std::mt19937 rng
std::ofstream ofile("RngState.txt");
ofile << rng;
ofile.close();

What I observe is the state is a vector of 1248 numbers And only 624 numbers get written in the file. Is there a way to write and read all the 1248 numbers in one attempt(I guess I am trying to increase the capacity/size of ofstream).

Thanks in advance.

Solution

  • As @knivil said, state could be represented with only 624 numbers. Please tell us how did you observe 1248?

    VS 2015

    EDIT:

    I have consistent results with this code, could you run it and check too?

    #include <fstream>
#include <random>
#include <iostream>

std::mt19937 deser(std::string fname)
{
  std::ifstream f{fname, std::ifstream::binary};
  std::mt19937  res;
  f >> res;
  return res;
}
void ser(std::string fname, std::mt19937 rng)
{
  std::ofstream f(fname, std::ofstream::binary);
  f << rng;
}

void printRand(std::mt19937 rng)
{
  std::uniform_int_distribution<> uid{1, 100};
  std::cout << uid(rng) << std::endl;
}

int main()
{
  auto fname{"R:\\RngState.txt"};

  std::mt19937 rng{std::random_device{}()};
  ser(fname, rng);
  printRand(rng);

  rng = deser(fname);
  printRand(rng);

  return 0;
}