Execution in local of a c-mpi program fails - c

Question

I want to run, on my local pc, this c-mpi program Receiver process have to print their portion of array in order of rank. This is my code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include "mpi.h"
#define MAX_DIM 22
#define NPROC 4
#define TRUE 1
#define FALSE 0
void print(int*,int*,int*,int*,int*,int*);
int main(int argc, char* argv[]){
int i,rank,*x,*y,nproc;
int partition=MAX_DIM/NPROC;
int sendcount[NPROC],offset[NPROC];
int k=MAX_DIM%NPROC;
for(i=0;i<NPROC;i++){
sendcount[i]=partition;
if(i<k)
sendcount[i]++;
}
offset[0]=0;
for(i=1;i<NPROC;i++)
offset[i]=offset[i-1]+sendcount[i-1];
MPI_Init(&argc,&argv);
MPI_Comm_size(MPI_COMM_WORLD,&nproc);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
if(rank==0){
srand(time(NULL));
x=(int*)malloc(sizeof(int)*MAX_DIM);
y=(int*)malloc(sizeof(int)*MAX_DIM);
for(i=0;i<MAX_DIM;i++){
x[i]=rand()%100+1;
y[i]=rand()%100+1;
}
printf("Sender[%d] => array <x>: \n",rank);
for(i=0;i<MAX_DIM;i++){
if(i%10==0)
printf("\n");
printf("%d ",x[i]);
}
printf("\nSender[%d] => array <y>: \n",rank);
for(i=0;i<MAX_DIM;i++){
if(i%10==0)
printf("\n");
printf("%d ",y[i]);
}
}
int* rvett1=(int*)malloc(sizeof(int)*sendcount[rank]);
int* rvett2=(int*)malloc(sizeof(int)*sendcount[rank]);
MPI_Scatterv(x,&sendcount[rank],&offset[rank],MPI_INT,rvett1,sendcount[rank],MPI_INT,0,MPI_COMM_WORLD);
MPI_Scatterv(y,&sendcount[rank],&offset[rank],MPI_INT,rvett2,sendcount[rank],MPI_INT,0,MPI_COMM_WORLD);
print(&rank,&nproc,rvett1,&sendcount[rank],rvett2,&sendcount[rank]);
if(rank==0){
free(x);
free(y);
}
free(rvett1);
free(rvett2);
MPI_Finalize();
printf("Exit program! \n");
return 0;
}
void print(int* rank,int* nproc,int* rvett1,int* dim1,int* rvett2,int* dim2){
int i,tag=0;
short int token=FALSE;
MPI_Status info;
if(*rank==0){
printf("\nReceiver[%d] => part of array <x>, dimension: %d \n",*rank,*dim1);
for(i=0;i<*dim1;i++){
if(i%10==0)
printf("\n");
printf("%d ",rvett1[i]);
}
printf("\nReceiver[%d] => part of array <y>, dimension: %d \n",*rank,*dim1);
for(i=0;i<*dim2;i++){
if(i%10==0)
printf("\n");
printf("%d ",rvett2[i]);
}
token=TRUE;
printf("\nStarter[%d] sends a print token \n",*rank);
MPI_Send(&token,1,MPI_SHORT_INT,1,tag+1,MPI_COMM_WORLD);
}
else{
for(i=1;i<*nproc;i++){
if(*rank==i){
MPI_Recv(&token,1,MPI_SHORT_INT,i-1,tag+i,MPI_COMM_WORLD,&info);
printf("Receiver[%d] => OK print \n ",i);
printf("\nReceiver[%d] => part of array <x>, dimension: %d \n",*rank,*dim1);
for(i=0;i<*dim1;i++){
if(i%10==0)
printf("\n");
printf("%d ",rvett1[i]);
}
printf("\nReceiver[%d] => part of array <y>, dimension: %d \n",*rank,*dim1);
for(i=0;i<*dim2;i++){
if(i%10==0)
printf("\n");
printf("%d ",rvett2[i]);
}
if(*rank<(*nproc)-1){
printf("Receiver[%d] sends next token \n",i);
MPI_Send(&token,1,MPI_SHORT_INT,i+1,tag+i+1,MPI_COMM_WORLD);
}
}
}
}
}
I use this 2 command to compile and execute the program:
mpicc -o sca_prod sca_prod.c
mpiexec -n 4 ./sca_prod
During the execution the program crash and it returns this error:
Sender[0] => array <x>:
92 37 80 73 68 24 42 72 88 26
47 25 24 98 47 92 72 100 34 20
76 97
Sender[0] => array <y>:
17 62 55 70 53 44 73 72 19 47
11 83 29 30 56 39 80 51 24 54
96 70
Receiver[0] => part of array <x>, dimension: 6
92 37 80 73 68 24
Receiver[0] => part of array <y>, dimension: 6
17 62 55 70 53 44
Starter[0] sends a print token
Receiver[1] => OK print
Receiver[1] => part of array <x>, dimension: 6
42 72 88 26 47 25
Receiver[1] => part of array <y>, dimension: 6
73 72 19 47 11 83 Receiver[6] sends next token
Fatal error in MPI_Send: Invalid rank, error stack:
MPI_Send(174): MPI_Send(buf=0x7ffe216fb636, count=1, MPI_SHORT_INT, dest=7, tag=7, MPI_COMM_WORLD) failed
MPI_Send(100): Invalid rank has value 7 but must be nonnegative and less than 4
I'm using MPICH3.2 with Hydra executor and my OS is Ubuntu 14.04; the machine has a quadcore i7 processor. Please, can you help me? Thank you so much!

Answer 1

You have two subtle issues:
MPI_SHORT_INT is the datatype in MPI for a struct { short, int }, for a short int use MPI_SHORT instead. This leads to overwriting memory.
You use i as loop variable in two nested loops.
In general your code could be structured more better, to avoid issues like the second one.
Declare variables as locally as possible, especially loop variables within the loop declaration (c99).
Use more descriptive variable names.
Hide things like printing an array in functions.
Format your code properly.
Also learn to use a (parallel) debugger.