如何修复关于Mandelbrot集的Pthreads代码？

我有以下关于计算和创建Mandelbrot集图片的Pthreads代码。 我在C中的代码工作正常，它很好地打印出结果图片。 关键是使用下面的代码，我能够编译代码并执行它。 之后，如果我尝试在Gimp中查看生成的.ppm文件，则无法打开它。 我想我在代码中做错了。 如果有人可以帮助我，我会很高兴。

// mandpthread.c // to compile: gcc mandpthread.c -o mandpthread -lm -lrt -lpthread // usage: ./mandpthread   > output.ppm #include  #include  #include  #include  #include  #include  typedef struct { int r, g, b; } rgb; int NITERATIONS, NTHREADS; rgb **m; void color(rgb **m, int x, int y, int red, int green, int blue) { m[y][x].r = red; m[y][x].g = green; m[y][x].b = blue; } void mandelbrot(int tid) { int w = 600, h = 400, x, y; // each iteration, it calculates: newz = oldz*oldz + p, // where p is the current pixel, and oldz stars at the origin double pr, pi; // real and imaginary part of the pixel p double newRe, newIm, oldRe, oldIm; // real and imaginary parts of new and old z double zoom = 1, moveX = -0.5, moveY = 0; // you can change these to zoom and change position int start = tid * NITERATIONS/NTHREADS; int end = (tid+1) * (NITERATIONS/NTHREADS) - 1; //loop through every pixel for(y = 0; y < h; y++) { for(x = 0; x < w; x++) { // calculate the initial real and imaginary part of z, // based on the pixel location and zoom and position values pr = 1.5 * (x - w / 2) / (0.5 * zoom * w) + moveX; pi = (y - h / 2) / (0.5 * zoom * h) + moveY; newRe = newIm = oldRe = oldIm = 0; //these should start at 0,0 // i will represent the number of iterations int i; // start the iteration process for(i = start; i  4) break; } if(i == NITERATIONS) color(m, x, y, 0, 0, 0); // black else { // normalized iteration count method for proper coloring double z = sqrt(newRe * newRe + newIm * newIm); int brightness = 256. * log2(1.75 + i - log2(log2(z))) / log2((double)NITERATIONS); color(m, x, y, brightness, brightness, 255); } } } } // worker function which will be passed to pthread_create function void *worker(void *arg) { int tid = (int)arg; mandelbrot(tid); } int main(int argc, char *argv[]) { pthread_t* threads; int i, j, rc; if(argc != 3) { printf("Usage: %s   > output.ppm\n", argv[0]); exit(1); } NITERATIONS = atoi(argv[1]); NTHREADS = atoi(argv[2]); threads = (pthread_t*)malloc(NTHREADS * sizeof(pthread_t)); m = malloc(400 * sizeof(rgb *)); for(i = 0; i < 400; i++) m[i] = malloc(600 * sizeof(rgb)); // declaring the needed variables for calculating the running time struct timespec begin, end; double time_spent; // starting the run time clock_gettime(CLOCK_MONOTONIC, &begin); printf("P6\n# AUTHOR: ET\n"); printf("%d %d\n255\n",600,400); for(i = 0; i < NTHREADS; i++) { rc = pthread_create(&threads[i], NULL, worker, (void *)i); assert(rc == 0); // checking whether thread creating was successfull } for(i = 0; i < NTHREADS; i++) { rc = pthread_join(threads[i], NULL); assert(rc == 0); // checking whether thread join was successfull } // printing to file for(i = 0; i < 400; i++) { for(j = 0; j < 600; j++) { fputc((char)m[i][j].r, stdout); fputc((char)m[i][j].g, stdout); fputc((char)m[i][j].b, stdout); } } // ending the run time clock_gettime(CLOCK_MONOTONIC, &end); // calculating time spent during the calculation and printing it time_spent = end.tv_sec - begin.tv_sec; time_spent += (end.tv_nsec - begin.tv_nsec) / 1000000000.0; fprintf(stderr, "Elapsed time: %.2lf seconds.\n", time_spent); for(i = 0; i < 400; i++) free(m[i]); free(m); free(threads); return 0; } 

Answer 1

最新版本的代码适用于100次迭代和1个线程。

执行两个线程失败，因为ppm文件有2个头文件，每个线程一个。

如果我删除其中一个标题，图像会加载，但颜色会关闭，图像中会出现毛刺。