I am working with a serial code and trying to parrallize it

I am working with a serial code and trying to parrallize it. The code is suppose to implement the sieve of Eratosthenes and find the primes up to a given limit. I continue to get this error message and would like to know what could be the fix?

#include
#include
#include
#include //looks in the include directory
static bool isPrime(long val)
{
if (val < 2) return false;
for (long i = 2; i * i <= val; i++) {
if ((val % i) == 0) return false;
}
return true;
}

int main(int argc, char *argv[])
{
int comm_sz;
int my_rank;

MPI_Init(NULL,NULL); //initializes MPI
MPI_Comm_size(MPI_COMM_WORLD, &comm_sz);
MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

if (my_rank == 0){
printf(\"Prime Sieve v1.0 [MPI]\ \"); //changed \"serial\" to \"MPI\"
}
// check command line
if (argc != 2) {fprintf(stderr, \"usage: %s maximum\ \", argv[0]); exit(-1);}
const long top = atol(argv[1]);
if (top < 23) {fprintf(stderr, \"error: maximum must be at least 23\ \"); exit(-1);}
printf(\"computing prime numbers up to but not including %ld\ \", top);

const int my_start = my_rank * (long)top / comm_sz;
const int my_end = (my_rank+1) * (long)top / comm_sz;

// allocate array
bool* array = new bool[top];

// start time
MPI_Barrier(MPI_COMM_WORLD);//barrier implemented before time start
timeval start, end;
gettimeofday(&start, NULL);

// initialize array
for (long i = 2 + my_rank; (i*i) < top; i+=comm_sz) { //assigned in a cylic
array[i] = true;
}

// remove multiples
for (long i = my_start; (i * i) < my_end; i++) { // just finished splitting array between processes, now
    long j = i * i;                                //I need to reduce into final array in the process 0
    while (j < top) {
      array[j] = false;
      j += i;
    }
}
// initiallize new array
bool* array2 = new bool[top];
    for (long i = 2 + my_rank; (i*i) < top; i+=comm_sz) { //assigned in a cylic
    array[i] = true;

// reduction
for (long i = my_start; i <= my_end; i++){
// if (array[i] == true){
MPI_Reduce(&array[i],&array2[i],1,MPI::BOOL,MPI_LXOR,0,MPI_COMM_WORLD);
}

// end time
gettimeofday(&end, NULL);
double runtime = end.tv_sec + end.tv_usec / 1000000.0 - start.tv_sec - start.tv_usec / 1000000.0;
printf(\"compute time: %.4f s\ \", runtime);

// print part of result from array2
if (my_rank == 0){
for (long i = 2; i < 10; i++) {
    if (array2[i]) {
      printf(\" %ld\", i);
    }
}
printf(\" ...\");
for (long i = top - 10; i < top; i++) {
    if (array2[i]) {
      printf(\" %ld\", i);
    }
}
printf(\"\ \");

// verify result
if (top < 10000000) {
    for (long i = 2; i < top; i++) {
      if (array2[i] != isPrime(i)) {
        fprintf(stderr, \"ERROR: wrong answer for %ld\ \ \", i);
        exit(-1);
      }
    }
}
}
delete [] array2;
delete [] array;
MPI_Finalize(); //finalizes mpi
return 0;
}
}

2 total processes failed to start [qwt10path finder Project2]$ mpirun n 2. /my executable. /sieve 2000000 mpirun was unable to launch the specified application as it could not access or execute an executable Executable ./myexecutable. /sieve Node pathfinder while attempting to start process rank 0.

Solution 1.

It may happen if you have already installed openMPI and not only MPICH2, then you should execute the below commands as root:

root~# update-alternatives --config mpirun

There are 2 choices for the alternative mpirun (providing /usr/bin/mpirun).

Selection | Path | Priority | Status

Then you should select the MPICH version, as above, to run normally.

Solution 2.

Put the full path to tau_exec in the command line. It is possible that your PATH is not the same on all the nodes. Then , it would not be able to locate the executable anywhere where the path isn\'t correct.

Note:

Don\'t remane the output file. Keep the default a.out as the name of output file.

I am working with a serial code and trying to parrallize it. The code is suppose to implement the sieve of Eratosthenes and find the primes up to a given limit.

I am working with a serial code and trying to parrallize it

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