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/*******************************************************************************
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* prob1-pipe.c - a pipeline method to calculate a McLauran series
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******************************************************************************/
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#include <mpi.h>
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#include <stdio.h>
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#include <stdlib.h>
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#define TAG_DATA 0xdddd
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int main (int argc, char *argv[])
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{
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int myid, numprocs;
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int *a, mya, x, n;
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float temp;
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MPI_Status status;
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MPI_Init (&argc, &argv);
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MPI_Comm_rank (MPI_COMM_WORLD, &myid);
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MPI_Comm_size (MPI_COMM_WORLD, &numprocs);
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if (myid == 0) /* root */
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{
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// allocate a
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// read a[i]'s
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// read n
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// read x
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}
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/* Do a sanity check.
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* We MUST have exactly enough processors available
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* to construct the pipeline. */
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if (numprocs != n)
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exit (1); // not enough processors
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/* Send everyone a single a value, and the x value */
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MPI_Scatter (a, 1, MPI_INT, &mya, 1, MPI_INT, 0, MPI_COMM_WORLD);
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MPI_Bcast (&x, 1, MPI_INT, 0, MPI_COMM_WORLD);
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if (myid == 0)
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{
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/* We are the root node, so do a single calculation, and then
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* forward the result on down the pipeline */
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temp = mya * pow (x, myid);
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MPI_Send (&temp, 1, MPI_FLOAT, myid+1, TAG_DATA, MPI_COMM_WORLD);
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}
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else if (myid < (numprocs - 1))
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{
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/* We are in the middle of the pipeline, so recieve a value from
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* our neighbor to the left, do a calculation, and pass the result
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* to our neighbor to the right */
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MPI_Recv (&temp, 1, MPI_FLOAT, myid-1, TAG_DATA, MPI_COMM_WORLD, &status);
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temp += mya * pow (x, myid);
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MPI_Send (&temp, 1, MPI_FLOAT, myid+1, TAG_DATA, MPI_COMM_WORLD);
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}
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else
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{
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/* We are at the end of the pipeline, so recieve a value from
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* our neightbor to the left, do a calculation, and print
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* the final resulting value */
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MPI_Recv (&temp, 1, MPI_FLOAT, myid-1, TAG_DATA, MPI_COMM_WORLD, &status);
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temp += mya * pow (x, myid);
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printf ("f = %e\n", temp);
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}
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MPI_Finalize ();
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return 0;
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}
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