C语言 C：信号代码：地址未映射 (1) mpirecv
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C: Signal code: Address not mapped (1) mpirecv
提问by Tato Tia
I have the following code written in C with MPI:
我用 MPI 用 C 编写了以下代码：
#include <mpi.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
int size, rank;
MPI_Status status;
int buf[1000];
MPI_Init(&argc, &argv);
MPI_Comm_size(MPI_COMM_WORLD, &size);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
if (rank == 0) {
int i = 0;
while (i != 1000) {
buf[i] = i;
i++;
}
MPI_Send(buf, 999, MPI_INT, 1, 1, MPI_COMM_WORLD);
printf("msg has been sent\n");
}
if (rank == 1) {
int sz = sizeof(buf);
int lst = buf[sz-1];
MPI_Recv(buf, 999, MPI_INT, 0, 1, MPI_COMM_WORLD, &status);
printf("la taille du buf %d et dernier %d", sz, lst);
}
MPI_Finalize();
}
And after run it it gives this message:
运行它后，它会给出以下消息：
msg has been sente
[blitzkrieg-TravelMate-P253:03395] *** Process received signal ***
[blitzkrieg-TravelMate-P253:03395] Signal: Segmentation fault (11)
[blitzkrieg-TravelMate-P253:03395] Signal code: Address not mapped (1)
[blitzkrieg-TravelMate-P253:03395] Failing at address: 0xbfee8574
[blitzkrieg-TravelMate-P253:03395] [0] [0xb772d40c]
[blitzkrieg-TravelMate-P253:03395] [1] mpii(main+0x12f) [0x8048883]
[blitzkrieg-TravelMate-P253:03395] [2] /lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf3) [0xb74c84d3]
[blitzkrieg-TravelMate-P253:03395] [3] mpii() [0x80486c1]
[blitzkrieg-TravelMate-P253:03395] *** End of error message ***
mpirun noticed that process rank 1 with PID 3395 on node blitzkrieg-
mpirun 注意到节点 blitzkrieg 上的进程等级为 1，PID 为 3395-
TravelMate-P253 exited on signal 11 (Segmentation fault).
TravelMate-P253 在信号 11（分段错误）上退出。
Any suggestion will help thnx.
任何建议都会有所帮助。
回答by Hristo Iliev
The stack trace shows that the error is not in the MPI_Recvas the question title suggests. The error is actually here:
堆栈跟踪显示错误不在MPI_Recv问题标题中。错误实际上在这里：
int sz = sizeof(buf);
int lst = buf[sz-1]; // <---- here
Since bufis an array of intand sizeof(buf)returns its size in bytes, szis set to 4 times the number of elements in the array. Accessing buf[sz-1]goes way beyond the bounds of bufand into an unmapped memory region above the stack of the process.
由于buf是一个数组int并sizeof(buf)以字节sz为单位返回其大小，因此设置为数组中元素数的 4 倍。访问buf[sz-1]超出buf了进程堆栈上方的未映射内存区域的边界并进入其中。
You should divide the total size of the array by the size of one of its elements, e.g. the first one:
您应该将数组的总大小除以其中一个元素的大小，例如第一个：
int sz = sizeof(buf) / sizeof(buf[0]);
int lst = buf[sz-1];
