Signal 11 (Segmentation fault) on MPI_Test - mpi

Question

I am receiving segmentation fault on MPI_Test in the following code. The code involves a sender process and a receiver process. The sender process uses non-blocking send to send an integer value to the receiver process 1000000 times. This is just a test code. I am receiving a segmentation fault on MPI_Test in the sender process and am not able to figure out the reason why.
int main(int argc, char* argv[]){
MPI_Init(&argc,&argv);
int rank,nodes;
int i,j;
MPI_Status stat;
int size,wait;
int msgs = atoi(argv[1]);
MPI_Comm_size(MPI_COMM_WORLD, &nodes);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Request req[msgs][nodes-1],req1;
if(rank==0){
size=2;
for(i=0;i<msgs;i++){
for(j=1;j<nodes;j++){
MPI_Isend(&size,1,MPI_INT,
j,0,MPI_COMM_WORLD,&(req[i][j-1]));
}
}
wait = 1;
i=0,j=0;
while(wait){
printf("at i=%d j=%d\n",i,j);
MPI_Test(&req[i][j], &wait, &stat);
wait = 1-wait;
if(!wait){
j++;
if(j==nodes-1){
j=0;
i++;
wait=1;
}
else{
wait=1;
}
if(i==msgs){
wait=0;
}
}
}
printf("Finished\n");
}
else{
for(i=0;i<msgs;i++){
MPI_Irecv (&size,1,MPI_INT,0,0,MPI_COMM_WORLD,&req1);
wait = 1;
while(wait){
MPI_Test(&req1, &wait, &stat);
wait = 1-wait;
}
if(size!=2){
printf("Received size=%d rank=%d\n",size,rank);
}
size=0;
}
printf("Finished rank=%d\n",rank);
}
MPI_Barrier(MPI_COMM_WORLD);
MPI_Finalize();
}
The output of the above program is:-
Finished
OK
OK
OK
OK
OK
after which it gives the segmentation fault
mpirun noticed that process rank 0 with PID 4576 exited on signal 11 (Segmentation fault).