Rank 2 caused collective abort of all racks - c++

Question

The code below tries to finds the max number of an array using mpi. However I keep getting the following error:
Rank 2 in job 47 caused collective abort of all ranks.
Exit status of rank 2 : killed by signal 9
Can anyone please tell me what's wrong?
#include <stdio.h>
#include <stdlib.h>
#include "mpi.h"
int main(int argc , char * argv[])
{
int myRank , numOfProcesses;
int source , destination;
int tag = 0;
int i = 0, j = 0, k = 0;
int masterArray[] = {5,6,8,10,12,3,9,-1,3,7};
int max , globalMax = -100000;
int flag = 0;
MPI_Init(&argc, &argv);
MPI_Status status;
MPI_Comm_rank(MPI_COMM_WORLD , &myRank);
MPI_Comm_size(MPI_COMM_WORLD , &numOfProcesses);
printf("Process : %d \n" , myRank);
int masterSize = sizeof(masterArray)/sizeof(int);
//printf("%d \n" , masterSize);
int slaveSize = masterSize/(numOfProcesses-1);
//printf("%d \n" , slaveSize);
int slaveArray[slaveSize];
if (myRank == 0){
for (i=1; i<numOfProcesses; i++){
for (j=0; j<slaveSize; j++){
slaveArray[j] = masterArray[k];
// printf("%d \n" , masterArray[k]);
k++;
}
MPI_Send(slaveArray, slaveSize, MPI_INT, i, tag, MPI_COMM_WORLD);
}
for (i=1; i<numOfProcesses; i++){
MPI_Recv(max , 1, MPI_INT, i, tag, MPI_COMM_WORLD, &status);
if (globalMax < max)
max = globalMax;
}
printf("Global Maximum %d \n" , globalMax);
}
else{
MPI_Recv(slaveArray , slaveSize, MPI_INT, 0, tag, MPI_COMM_WORLD, &status);
max = slaveArray[0];
for (i=0; i<slaveSize; i++){
if (slaveArray[i] > max)
max = slaveArray[i];
}
printf("Max in %d %d \n" , myRank, max);
MPI_Send(max , 1, MPI_INT, 0, tag, MPI_COMM_WORLD);
}
MPI_Finalize();
return 0;
}

Answer 1

Sending and receiving messages in MPI always works through addresses. In the following:
MPI_Recv(max , 1, MPI_INT, i, tag, MPI_COMM_WORLD, &status);
...
MPI_Send(max , 1, MPI_INT, 0, tag, MPI_COMM_WORLD);
You use the value. You must add & to take the address.
You should also learn to use the appropriate collective operations: MPI_Scatter and MPI_Reduce.
By the way, this line is also in the wrong order:
max = globalMax;
Please also learn to listen to your compiler! Any reasonable compiler at resonable settings will warn you of passing an integer as an address.