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POThe same random numbers for each process in c++ code with MPI
 

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  1. POThe same random numbers for each process in c++ code with MPI
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    <p>I have C++ MPI code that works, in that it compiles and does indeed launch on the specified number of processors (<em>n</em>). The problem is that it simply does the same calculation <em>n</em> times, rather than doing one calculation <em>n</em> times faster.</p> <p>I have hacked quite a few examples I have found on various sites, and it appears I am missing the proper use of MPI_Send and MPI_Receive, but I can't find an instance these commands that takes a function as input (and am confused as to why these MPI commands would be useful for anything other than functions).</p> <p>My code is below. Essentially it calls a C++ function I wrote to get Fisher's Exact Test p-value. The random-number bit is just something I put in to test the speed.</p> <p>What I want is for this program to do is farm out <em>Fisher.TwoTailed</em> with each set of random variables (i.e., <em>A</em>, <em>B</em>, <em>C</em>, and <em>D</em>) to a different processor, rather than doing the exact same calculation on multiple processors. Thanks in advance for any insight--cheers!</p> <p>Here is the code: </p> <pre><code>int main (int argc, char* argv[]) { int id; int p; // // Initialize MPI. // MPI::Init ( argc, argv ); // // Get the number of processors. // p = MPI::COMM_WORLD.Get_size ( ); // // Get the rank of this processor. // id = MPI::COMM_WORLD.Get_rank ( ); FishersExactTest Fishers; int i = 0; while (i &lt; 10) { int A = 0 + rand() % (100 - 0); int B = 0 + rand() % (100 - 0); int C = 0 + rand() % (100 - 0); int D = 0 + rand() % (100 - 0); cout &lt;&lt; Fishers.TwoTailed(A, B, C, D) &lt;&lt; endl; i += 1; } MPI::Finalize ( ); return 0; } </code></pre>
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