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rSCINTROPARALLEL/io_binary_mpi_io.c
26cfdaf7db47implementation/c++

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io_binary_mpi_io.c
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#include "io_binary_mpi_io.h"
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
#ifndef min
#define min(a, b) (((a) < (b)) ? (a) : (b))
#endif
static void write_bmp(int w, int h, float * u, unsigned int iter, float minval,
float maxval) {
int prank, psize;
MPI_Comm_rank(MPI_COMM_WORLD, &prank);
MPI_Comm_size(MPI_COMM_WORLD, &psize);
int i, j;
int padding, filesize;
float v, r, g, b;
MPI_File fh;
MPI_Status status;
char filename[8 + 4 + 1] = {'0'};
char prefix[] = "out_";
char suffix[] = ".bmp";
sprintf(filename, "%s%05d%s", prefix, iter, suffix);
int row_size = 3 * w;
// if the file width (3*w) is not a multiple of 4 adds enough bytes to make it
// a multiple of 4
padding = (4 - (row_size) % 4) % 4;
row_size += padding;
int buf[psize];
MPI_Allgather(&h, 1, MPI_INT, buf, 1, MPI_INT, MPI_COMM_WORLD);
int offset_h = 0;
for (i = 0; i < prank; ++i) {
offset_h += buf[i];
}
int total_h = offset_h;
for (i = prank; i < psize; ++i) {
total_h += buf[i];
}
filesize = 54 + row_size * total_h;
int offset = 54 + row_size * offset_h;
unsigned char * img;
img = (unsigned char *)calloc((row_size)*h, 1);
for (i = 0; i < h; i++) {
for (j = 0; j < w; j++) {
v = ((u[i * w + j] - minval) / (maxval - minval));
r = v * 255; // Red channel
g = v * 255; // Green channel
b = v * 255; // Red channel
r = min(r, 255);
g = min(g, 255);
b = min(b, 255);
img[row_size * i + 3 * j + 2] = (unsigned char)(r);
img[row_size * i + 3 * j + 1] = (unsigned char)(g);
img[row_size * i + 3 * j + 0] = (unsigned char)(b);
}
}
unsigned char bmpfileheader[14] = {'B', 'M', 0, 0, 0, 0, 0,
0, 0, 0, 54, 0, 0, 0};
unsigned char bmpinfoheader[40] = {40, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 1, 0, 24, 0};
bmpfileheader[2] = (unsigned char)(filesize);
bmpfileheader[3] = (unsigned char)(filesize >> 8);
bmpfileheader[4] = (unsigned char)(filesize >> 16);
bmpfileheader[5] = (unsigned char)(filesize >> 24);
bmpinfoheader[4] = (unsigned char)(w);
bmpinfoheader[5] = (unsigned char)(w >> 8);
bmpinfoheader[6] = (unsigned char)(w >> 16);
bmpinfoheader[7] = (unsigned char)(w >> 24);
bmpinfoheader[8] = (unsigned char)(total_h);
bmpinfoheader[9] = (unsigned char)(total_h >> 8);
bmpinfoheader[10] = (unsigned char)(total_h >> 16);
bmpinfoheader[11] = (unsigned char)(total_h >> 24);
bmpinfoheader[20] = (unsigned char)((filesize - 54));
bmpinfoheader[21] = (unsigned char)((filesize - 54) >> 8);
bmpinfoheader[22] = (unsigned char)((filesize - 54) >> 16);
bmpinfoheader[23] = (unsigned char)((filesize - 54) >> 24);
MPI_File_open(MPI_COMM_WORLD, filename, MPI_MODE_WRONLY | MPI_MODE_CREATE,
MPI_INFO_NULL, &fh);
MPI_File_set_size(fh, filesize);
if (prank == 0) {
MPI_File_write_at(fh, 0, bmpfileheader, 14, MPI_CHAR, &status);
MPI_File_write_at(fh, 14, bmpinfoheader, 40, MPI_CHAR, &status);
}
// We also could write that data with a write_at, the view is just to show
// different possibilities
MPI_File_set_view(fh, offset, MPI_CHAR, MPI_CHAR, "native",
MPI_INFO_NULL);
MPI_File_write(fh, img, row_size * h, MPI_CHAR, &status);
MPI_File_close(&fh);
free(img);
}
void write_to_file(int n, int n_loc, float * x, unsigned int iter, float minval,
float maxval) {
write_bmp(n, n_loc, x, iter, minval, maxval);
}
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