How fix it. Unhandled exception at 0x0099B514 in ConsoleApplication15.exe: 0xC0000094: Integer division by zero - c++11

Question

I am trying to solve problem with c++: Find all unique elements of a two-dimensional array of integers using MPI_Scatter and MPI_Comm_split to distribute the array's rows among a set of processes, so that the set of processes is split into three groups.
Got the code
#include <iostream>
#include <unordered_set>
#include <mpi.h>
using namespace std;
int main(int argc, char* argv[])
{
int rank, size;
int rows = 0, columns = 0;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
int* matrix = nullptr;
if (rank == 0)
{
cout << "Enter the number of rows: ";
cin >> rows;
cout << "Enter the number of columns: ";
cin >> columns;
matrix = new int[rows * columns];
cout << "Enter the elements of the matrix: " << endl;
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < columns; j++)
{
cin >> matrix[i * columns + j];
}
}
}
MPI_Bcast(&rows, 1, MPI_INT, 0, MPI_COMM_WORLD);
MPI_Bcast(&columns, 1, MPI_INT, 0, MPI_COMM_WORLD);
int sub_size = rows / size;
int* local_matrix = new int[sub_size * columns];
MPI_Scatter(matrix, sub_size * columns, MPI_INT, local_matrix, sub_size * columns, MPI_INT, 0, MPI_COMM_WORLD);
unordered_set<int> local_set;
for (int i = 0; i < sub_size; i++)
{
for (int j = 0; j < columns; j++)
{
local_set.insert(local_matrix[i * columns + j]);
}
}
MPI_Comm sub_comm;
MPI_Comm_split(MPI_COMM_WORLD, rank / (size / 3), rank, &sub_comm);
int sub_rank, new_sub_size;
MPI_Comm_rank(sub_comm, &sub_rank);
MPI_Comm_size(sub_comm, &new_sub_size);
unordered_set<int>* global_set = nullptr;
if (sub_rank == 0)
{
global_set = new unordered_set<int>[new_sub_size];
}
MPI_Gather(&local_set, sizeof(unordered_set<int>), MPI_BYTE, global_set, sizeof(unordered_set<int>), MPI_BYTE, 0, sub_comm);
if (sub_rank == 0)
{
unordered_set<int> final_set;
for (int i = 0; i < new_sub_size; i++)
{
for (auto it = global_set[i].begin(); it != global_set[i].end(); it++) {
final_set.insert(*it);
}
}
cout << "The unique elements in the matrix are: ";
for (auto it = final_set.begin(); it != final_set.end(); it++) {
cout << *it << " ";
}
cout << endl;
delete[] global_set;
}
delete[] local_matrix;
if (rank == 0) {
delete[] matrix;
}
MPI_Finalize();
return 0;
}
After compile and input data microsoft visual studio 2019 gives an error message
Unhandled exception at 0x0099B514 in ConsoleApplication15.exe: 0xC0000094: Integer division by zero.
to this line
MPI_Comm_split(MPI_COMM_WORLD, rank / (size / 3), rank, &sub_comm);
How fix it?