I am currently running a multithreading simulation application with 8+ pipes (threads). These pipes run a very complex code that depends on a random sequence generated by a seed. The sequence is then boiled down to a single 0/1.
I want this "random processing" to be 100% deterministic after passing a seed to the processing pipe from the main thread. So, I can replicate the results in a second run.
So, for example: (I have this coded and it works)
Pipe 1 -> Seed: 123 -> Result: 0
Pipe 2 -> Seed: 123 -> Result: 0
Pipe 3 -> Seed: 589 -> Result: 1
The problem arises when I need to run 100M or more of these processes and then average the results. It may be the case only 1 of the 100M is a 1, and the rest are 0.
As it is obvious, I cannot sample 100M random values with 32bit seeds feeding to srand().
Is it possible to seed with a 64bit seed in VS2010 to srand(), or use a equivalent approach?
Does rand() repeat itself after 2^32 or does not (has some inner hidden state)?
Thanks
You can use C++11's random facilities to generate random numbers of a given size and seed size, though the process is a bit too complicated to summarize here.
For example, you can construct an std::mersenne_twister<uint64_t, ...> and seed it with a 64-bit integer, then acquire random numbers within a specified distribution, which seems to be what you're looking for.