Escali manual Scali MPI Connect Release 4.4 Users Guide

/* read the image */

for ( i = 0; i < numpixels; i ++ )

{

fscanf( infile, "%u", &buffer ); pixels[i] = (unsigned char)buffer;

}

fclose( infile );

/* calculate number of pixels for each node */ my_count = numpixels / size;

}

/* broadcast to all nodes */

MPI_Bcast( &my_count, 1, MPI_INT, 0, MPI_COMM_WORLD ); /* scatter the image */

MPI_Scatter( pixels, my_count, MPI_UNSIGNED_CHAR, recvbuf, my_count, MPI_UNSIGNED_CHAR, 0, MPI_COMM_WORLD );

/* sum the squares of the pixels in the sub-image */ my_sum = 0;

for ( i = 0; i < my_count; i ++ ) my_sum += recvbuf[i] * recvbuf[i];

/* find the global sum of the squares */

MPI_Reduce( &my_sum, &sum, 1, MPI_INT, MPI_SUM, 0, MPI_COMM_WORLD ); /* let rank 0 compute the root mean square */

if ( rank == 0 )

{

rms = sqrt( (double)sum / (double)numpixels );

}

/* rank 0 broadcasts the RMS to the other nodes */ MPI_Bcast( &rms, 1, MPI_DOUBLE, 0, MPI_COMM_WORLD );

/* perform filtering operation (contrast enhancement) */ for ( i = 0; i < my_count; i ++ )

{

val = 2 * recvbuf[i] - rms;

if ( val < 0 ) recvbuf[i] = 0;

else if ( val > 255 ) recvbuf[i] = 255; else recvbuf[i] = val;

}

/* gather back to rank 0 */

MPI_Gather( recvbuf, my_count, MPI_UNSIGNED_CHAR, pixels, my_count, MPI_UNSIGNED_CHAR, 0, MPI_COMM_WORLD );

/* dump the image from rank 0 */ if ( rank == 0 )

{

outfile = fopen( "try.pgm", "w" ); if ( ! outfile )

{

printf("unable to open try.ppm\n");

}

else

{

fprintf( outfile, "%s\n", (unsigned char*)line ); fprintf( outfile, "%d %d\n", height, width ); fprintf( outfile, "255\n");

/*numpixels = height * width; */ for ( i = 0; i < numpixels; i ++ )

{

fprintf( outfile, "%d\n", (int)pixels[i] );

Scali MPI Connect Release 4.4 Users Guide 52