我在此程序中使用消息队列时遇到问题 它应该启动一些由命令提示符通过参数传递给程序的进程，但它只启动并计算一个进程的点...其他进程无法启动.. 请帮帮我。
这是创建消息队列并将所选数据输出为pgm格式的程序 只有第一个进程才能运行其他进程 谁能告诉我为什么？
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <stdlib.h>
#include <string.h>
void output_pgm(char *filename,double *buffer, int nx, int ny, double max) {
int i;
FILE *file;
file = fopen(filename,"w");
fprintf(file,"P2\n");
fprintf(file,"%d %d\n",nx,ny);
fprintf(file,"%d\n",(int)max);
for (i=0; i<nx*ny; i++) {
if (!(i%nx)) fprintf(file,"\n");
fprintf(file,"%d ",(int)buffer[i]);
}
fclose(file);
}
void main(int argc,char *argv[]) {
if(argc != 2) {
} else {
int n = atoi(argv[1]);
int i = 0;
struct msgbuf {
long mtype;
int x;
int y;
double value;
};
struct envio {
long mtype;
long type;
int ny;
double yM1;
double yM2;
};
key_t key = 123;
key_t key2 = 124;
int msgflg = IPC_CREAT | 0666;
int msqid = msgget(key,msgflg);
int msqid2 = msgget(key2,msgflg);
switch(fork()) {
case -1:
printf("Erro de fork");
break;
case 0:
printf("Oi: %d\n",n);
double *b;
int x,y,i,m;
double *ptr = b = malloc(1000*1000*sizeof(double));
printf("Chego(1)\n");
struct msgbuf a;
struct envio c;
size_t buflen = sizeof(a) - sizeof(long);
size_t len2 = sizeof(c) - sizeof(long);
printf("Chego(2)\n");
int msid = msgget(key,msgflg);
int msid2 = msgget(key2,msgflg);
printf("Chego(3)\n");
double aux = -1.0;
double multiplier = ((1.0/n) * 2);
c.mtype = 300;
int ny = (int)(1000/n);
for(i = 0; i < n; i++) {
c.type = (i+1);
c.ny = (int)(1000/n);
c.yM1 = aux;
c.yM2 = aux+multiplier;
printf("Chego aqui(2)\n");
if(msgsnd(msid2,&c,len2,0) < 0) {
perror("Erro do 1o envio\n");
}
}
for(m = 0; m < n; m++) {
printf("Entrei no ciclo(1)\n");
for(y = 0; y <ny ;y++) {
//printf("Chego(4)\n");
for(x = 0; x < 1000;x++) {
if(msgrcv(msid,&a,buflen,(long)(m+1),0) < 0) {
perror("Erro na recepcao:\n ");
}
//printf("Chego(5)\n");
b[a.y * ny + a.x] = a.value;
}
}
b = b + (1000/n)*1000;
}
output_pgm("mandel.pgm", ptr, 1000, 1000, 255);
//msgctl(msid, IPC_RMID, NULL);
//msgctl(msid2, IPC_RMID, NULL);
printf("Processo 1\n");
break;
default:
for(i = 0;i < n;i++) {
switch(fork()) {
case -1:
printf("Erro de fork");
case 0:
exit(0);
break;
default:
printf("Fui lancado\n");
execlp("/home/hyper/Documents/SO2/TP3-4/rec","rec",0);
break;
}
}
break;
}
}
};
此程序中的for循环仅运行一次
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <stdlib.h>
#include <string.h>
double type;
struct senbuf {
long mtype;
int x;
int y;
double value;
};
int max_iterations = 256;
double compute_point(double ci, double cr) {
int iterations = 0;
double zi = 0;
double zr = 0;
while ((zr*zr + zi*zi < 4) && (iterations < max_iterations)) {
double nr, ni;
/* Z <-- Z^2 + C */
nr = zr*zr - zi*zi + cr;
ni = 2*zr*zi + ci;
zi = ni;
zr = nr;
iterations ++;
}
return iterations;
}
/* The "compute" function computes the Mandelbrot function over every
point on a grid that is "nx" points wide by "ny" points tall, where
(xmin,ymin) and (xmax,ymax) give two corners of the region the
complex plane.
*/
void compute(int msqid,int nx, int ny, double xmin, double xmax,
double ymin, double ymax,long type2 ) {
double delta_x, delta_y;
int x, y;
struct senbuf sen;
delta_x = (xmax - xmin)/nx;
delta_y = (ymax - ymin)/ny;
size_t buflen = sizeof(sen) - sizeof(long);
for (y=0; y<ny; y++) {
//printf("Ja entrei aqui");
double y_value = ymin + delta_y * y;
for (x=0; x<nx; x++) {
double x_value = xmin + delta_x * x;
sen.mtype = type;
sen.x = x;
sen.y = y;
sen.value = compute_point(x_value,y_value);
if(msgsnd(msqid,&sen,buflen,0) < 0) {
perror("Erro no envio:");
};
// printf("%f",sen.a[y*nx + x]);
//buffer[y*nx + x] = compute_point(x_value, y_value);
}
}
printf("Ja mandei %d\n",type2);
/*sen.mtype=500;
sen.test = -1;
printf("Ja to a sair\n");
msgsnd(msqid,&sen,buflen,IPC_NOWAIT);*/
}
/* Output the data contained in the buffer to a Portable Greymap format
image file. The parameter "max" should be an upper bound for the
data values in the buffer.
*/
void output_pgm(char *filename,double *buffer, int nx, int ny, double max) {
int i;
FILE *file;
file = fopen(filename,"w");
fprintf(file,"P2\n");
fprintf(file,"%d %d\n",nx,ny);
fprintf(file,"%d\n",(int)max);
for (i=0; i<nx*ny; i++) {
if (!(i%nx)) fprintf(file,"\n");
fprintf(file,"%d ",(int)buffer[i]);
}
fclose(file);
}
int main()
{
int msqid;
int msqid2;
struct recep {
long mtype;
long type;
int ny;
double yM1;
double yM2;
};
struct recep a;
size_t len = sizeof(a) - sizeof(long);
key_t key = 124;
msqid = msgget(key, 0666);
if(msgrcv(msqid, &a, len, 300, 0) < 0) {
perror("Error checking");
};
printf("Dados :\n Tipo : %d\n Ny: %d\n,yM1 : %f\n yM2: %f\n",a.type,a.ny,a.yM1,a.yM2);
type = a.type;
printf("Vou iniciar o compute");
key_t key2 = 123;
msqid2 = msgget(key2,0666);
compute(msqid2,1000,a.ny, -1.0, 1.0,a.yM1,a.yM2,a.type);
}
答案 0 :(得分：1)
在你的第一个switch语句中，你创建了一个正在做任何事情的孩子。父进入第二个switch语句，其中子进程立即退出，父进程覆盖“rec”可执行文件。父级不再执行 - 它是程序“rec”。你永远不会执行循环的多次传递，因为正在执行的代码在那时就消失了。如果你想要运行“rec”的多个实例，你应该对孩子而不是父母使用execlp。
修改
有两个系统调用wait和waitpid，提供各种选项。其中较简单的是wait，应该足以满足您的需求。在您创建的每个子项的父项中定义和增加计数器。然后，不是只退出父母，而是等待所有孩子完成。这样简单就足够了：
for (int i = 0; i < counter; i++)
{
wait(NULL);
}