program ended prematurely and may have crashed. exit code 0xc0000005 - c++

Question

Here is my code I want to multiply a 2D array with a vector array:
#include<iostream>
#include<mpi.h>
using namespace std;
int v_array[10] ;
int ch_size, start, close;
int res ;
int rows, cols;
int main(int argc, char *argv[])
{
int pro_id, tot_pros;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &pro_id);
MPI_Comm_size(MPI_COMM_WORLD, &tot_pros);
if (pro_id == 0) {
cout << "Enter rows and columns: ";
cin >> rows >> cols;
int **array = new int*[rows];
int size1 = rows * cols;
array[0] = new int[size1];
for (int j = 1; j < rows; j++) {
array[j] = &array[0][j*cols];
}
for (int i = 0; i < rows; i++) {
v_array[i] = 1;
for (int j = 0; j < cols; j++) {
array[i][j] = 1;
}
}
for (int i = 1; i < tot_pros; i++) {
ch_size = (rows / (tot_pros - 1));
start = (i - 1) * ch_size;
if (((i + 1) == tot_pros) && ((rows % (tot_pros - 1)) != 0)) {
close = rows;
}
else {
close = start + ch_size;
}
MPI_Send(&start, 1, MPI_INT, i, 1, MPI_COMM_WORLD);
MPI_Send(&close, 1, MPI_INT, i, 2, MPI_COMM_WORLD);
MPI_Send(&cols, 1, MPI_INT, i, 4, MPI_COMM_WORLD);
MPI_Send(&array[start][0], ch_size *cols, MPI_INT, i, 3, MPI_COMM_WORLD);
}
}
else
{
int cols;
MPI_Recv(&start, 1, MPI_INT, 0, 1, MPI_COMM_WORLD, MPI_STATUSES_IGNORE);
MPI_Recv(&close, 1, MPI_INT, 0, 2, MPI_COMM_WORLD, MPI_STATUSES_IGNORE);
MPI_Recv(&cols, 1, MPI_INT, 0, 4, MPI_COMM_WORLD, MPI_STATUSES_IGNORE);
int **array = new int*[(close - start)*cols];
MPI_Recv(array, (close - start) *cols , MPI_INT, 0, 3, MPI_COMM_WORLD, MPI_STATUSES_IGNORE);
for (int i = start; i < close; i++) {
for (int j = 0; j < cols; j++) {
cout << array[i]<<array[j];
res += array[i][j] * v_array[i];
cout << res;
}
}
}
MPI_Finalize();
return 0;
}
This same program is working fine when I have static array, But with dynamic I got this error.
E:\MS(CS)\2nd Semester\Parallel
Programing\programs\arr_multi\Debug>mpiexec -n 4 arr_multi.exe Enter
rows and columns: 3 2
job aborted: [ranks] message
[0-1] terminated
[2] process exited without calling finalize
[3] terminated
---- error analysis -----
[2] on RAMISHA-PC arr_multi.exe ended prematurely and may have
crashed. exit code 0xc0000005
---- error analysis -----
I declared an array with contiguous location and my rows are divided correctly among processes. I think I have problem with my data structure and tried many solutions but in vain.

Answer 1

First and foremost, there are ways to debug an MPI application, which should really be your top priority. A general approach for multi-process applications is to pause at the beginning of your application e.g. with a getchar() then attach to each process with a debugger as described here:
compile, link and start running your MPI program (you may wish to put a read statement early on to hold the program while you do the next steps)
attach to one of the currently running MPI processes: Debug - Attach to Process brings up a dialogue box which lists Available Processes. You should see NUM instances (where N is from mpiexec -n NUM) of your executable. Select all of these and click on Attach. You can now debug by adding breakpoints etc. To move between MPI processes use the Process drop-down menu just above the code listing.
Having said that, at least one of the problems is with this part: int **array = new int*[(close - start)*cols]; (in the receive part of the application). You allocate the first dimension but not the second, so all pointers in the first dimension are uninitialized.
Change it to something like:
int *array = new int[(close - start) * cols];
MPI_Recv(array, (close - start) *cols, MPI_INT, 0, 3, MPI_COMM_WORLD, MPI_STATUSES_IGNORE);
for (int i = start; i < close; i++) {
for (int j = 0; j < cols; j++) {
cout << array[(i - start) * cols];
res += array[(i - start) * cols] * v_array[i];
cout << res;
}
}
delete[] array;
Or if you really want to use a 2D array, copy the initialization code from the sending part:
int rows = close - start;
int **array = new int*[rows];
int size1 = rows * cols;
array[0] = new int[size1];
for (int j = 1; j < rows; j++) {
array[j] = &array[0][j*cols];
}
The second problem is that v_array, being a global is not initialized in your receiver processes. Remember that in MPI each process is an independent program. So you should initialize v_array always, i.e. regardless of pro_id.
for (int i = 0; i < rows; i++) {
v_array[i] = 1;
}