MPI Search In Array - c

Question

Im trying to find a spesific value inside an array. Im trying to find it with parallel searching by mpi. When my code finds the value, it shows an error.
ERROR
Assertion failed in file src/mpid/ch3/src/ch3u_buffer.c at line 77: FALSE
memcpy argument memory ranges overlap, dst_=0x7ffece7eb590 src_=0x7ffece7eb590 len_=4
PROGRAM
const char *FILENAME = "input.txt";
const size_t ARRAY_SIZE = 640;
int main(int argc, char **argv)
{
int *array = malloc(sizeof(int) * ARRAY_SIZE);
int rank,size;
MPI_Status status;
MPI_Request request;
int done,myfound,inrange,nvalues;
int i,j,dummy;
/* Let the system do what it needs to start up MPI */
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Comm_size(MPI_COMM_WORLD,&size);
myfound=0;
if (rank == 0)
{
createFile();
array = readFile(FILENAME);
}
MPI_Bcast(array, ARRAY_SIZE, MPI_INT, 0, MPI_COMM_WORLD);
MPI_Irecv(&dummy, 1, MPI_INT, MPI_ANY_SOURCE, 1, MPI_COMM_WORLD, &request);
MPI_Test(&request, &done, &status);
nvalues = ARRAY_SIZE / size; //EACH PROCESS RUNS THAT MUCH NUMBER IN ARRAY
i = rank * nvalues; //OFFSET FOR EACH PROCESS INSIDE THE ARRAY
inrange = (i <= ((rank + 1) * nvalues - 1) && i >= rank * nvalues); //LIMIT OF THE OFFSET
while (!done && inrange)
{
if (array[i] == 17)
{
dummy = 1;
for (j = 0; j < size; j++)
{
MPI_Send(&dummy, 1, MPI_INT, j, 1, MPI_COMM_WORLD);
}
printf("P:%d found it at global index %d\n", rank, i);
myfound = 1;
}
printf("P:%d - %d - %d\n", rank, i, array[i]);
MPI_Test(&request, &done, &status);
++i;
inrange = (i <= ((rank + 1) * nvalues - 1) && i >= rank * nvalues);
}
if (!myfound)
{
printf("P:%d stopped at global index %d\n", rank, i - 1);
}
MPI_Finalize();
}
Error is somewhere in here because when i put an invalid number for example -5 into if condition, program runs smoothly.
dummy = 1;
for (j = 0; j < size; j++)
{
MPI_Send(&dummy, 1, MPI_INT, j, 1, MPI_COMM_WORLD);
}
printf("P:%d found it at global index %d\n", rank, i);
myfound = 1;
Thanks

Answer 1

Your program is invalid with respect to the MPI standard because you use the same buffer (&dummy) for both MPI_Irecv() and MPI_Send().
You can either use two distinct buffers (e.g. dummy_send and dummy_recv), or since you do not seem to care about the value of dummy, then use NULL as buffer and send/receive zero size messages.