139 lines
3.7 KiB
C
139 lines
3.7 KiB
C
#include <math.h>
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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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#include <string.h>
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#define XSIZE 2560
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#define YSIZE 2048
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#define MAXITER 255
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double xleft = -2.01;
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double xright = 1;
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double yupper, ylower;
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double ycenter = 1e-6;
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double step;
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int pixel[XSIZE * YSIZE];
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#define PIXEL(i, j) ((i) + (j) * XSIZE)
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typedef struct {
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double real, imag;
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} complex_t;
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int rank, size;
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void calculate() {
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for (int i = 0; i < XSIZE; i++) {
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for (int j = 0; j < YSIZE; j++) {
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/* Calculate the number of iterations until divergence for each pixel.
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If divergence never happens, return MAXITER */
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complex_t c, z, temp;
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int iter = 0;
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c.real = (xleft + step * i);
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c.imag = (ylower + step * j);
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z = c;
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while (z.real * z.real + z.imag * z.imag < 4) {
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temp.real = z.real * z.real - z.imag * z.imag + c.real;
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temp.imag = 2 * z.real * z.imag + c.imag;
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z = temp;
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if (++iter == MAXITER)
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break;
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}
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pixel[PIXEL(i, j)] = iter;
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}
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}
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}
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typedef unsigned char uchar;
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/* save 24-bits bmp file, buffer must be in bmp format: upside-down */
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void savebmp(char *name, uchar *buffer, int x, int y) {
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FILE *f = fopen(name, "wb");
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if (!f) {
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printf("Error writing image to disk.\n");
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return;
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}
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unsigned int size = x * y * 3 + 54;
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uchar header[54] = { 'B', 'M', size & 255, (size >> 8) & 255, (size >> 16) & 255, size >> 24, 0,
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0, 0, 0, 54, 0, 0, 0, 40, 0, 0, 0, x & 255, x >> 8, 0, 0, y & 255, y >> 8, 0, 0, 1, 0, 24, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
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fwrite(header, 1, 54, f);
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fwrite(buffer, 1, XSIZE * YSIZE * 3, f);
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fclose(f);
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}
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/* given iteration number, set a colour */
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void fancycolour(uchar *p, int iter) {
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if (iter == MAXITER)
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;
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else if (iter < 8) {
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p[0] = 128 + iter * 16;
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p[1] = p[2] = 0;
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} else if (iter < 24) {
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p[0] = 255;
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p[1] = p[2] = (iter - 8) * 16;
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} else if (iter < 160) {
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p[0] = p[1] = 255 - (iter - 24) * 2;
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p[2] = 255;
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} else {
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p[0] = p[1] = (iter - 160) * 2;
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p[2] = 255 - (iter - 160) * 2;
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}
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}
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int main(int argc, char **argv) {
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MPI_Init(&argc, &argv);
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MPI_Comm_rank(MPI_COMM_WORLD, &rank);
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MPI_Comm_size(MPI_COMM_WORLD, &size);
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step = (xright - xleft) / XSIZE;
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double old_yupper = ycenter + (step * YSIZE) / 2;
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double old_ylower = ycenter - (step * YSIZE) / 2;
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double delta = (old_yupper - old_ylower) / size;
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ylower = old_ylower + rank * delta;
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yupper = old_ylower + (rank + 1) * delta;
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calculate();
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printf("after calculate %d\n", rank);
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const int bufsize = XSIZE * YSIZE * 3;
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unsigned char *buffer = calloc(bufsize, 1);
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for (int i = 0; i < XSIZE; i++) {
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for (int j = 0; j < YSIZE; j++) {
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int p = ((YSIZE - j - 1) * XSIZE + i) * 3;
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fancycolour(buffer + p, pixel[PIXEL(i, j)]);
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}
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}
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printf("after buffer %d\n", rank);
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if (rank != 0)
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MPI_Send(buffer, bufsize, MPI_INT8_T, 0, 0, MPI_COMM_WORLD);
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printf("hello again from %d\n", rank);
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// use process 0 as central process: gather calulations and output image
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if (rank == 0) {
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unsigned char *bufferest = calloc(bufsize * size, 1);
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memcpy(bufferest, buffer, bufsize);
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printf("after memcpy\n");
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for (int i = 1; i < size; i++) {
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MPI_Recv(buffer, bufsize, MPI_INT8_T, i, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
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memcpy(bufferest + bufsize * i, buffer, bufsize);
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}
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printf("after loop\n");
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savebmp("mandel.bmp", buffer, XSIZE, YSIZE * size);
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printf("after save\n");
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}
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MPI_Finalize();
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return 0;
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}
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