Beowulf specifications

• Nodes: 17 (1 frontend + 16 compute nodes)
• Processor Specifications:
  • frontend: 2 x 2.40 GHz GenuineIntel Intel(R) Xeon(TM) with HyperThreading
  • Each compute node: 1 x 2.4 GHz GenuineIntel Intel(R) Xeon(TM) with HyperThreading
• Memory:
  • frontend: 4 GB
  • Each compute node: 2 GB
• Network: Nodes are connected by Gigabit Ethernet.

Caveats

Logging In

Compiling Programs

Running code

Timing your runs

Installed Libraries

• MPI
• ATLAS
• LAPACK
• BLACS
• ScaLAPACK
• FFTW

MPI example

#include "mpi.h"
#include "unistd.h"
#include "stdio.h"

int main(int argc, char **argv) {

  size_t len=256;
  char *hostname = new char[len];
  int size,rank;

  MPI_Init(&argc, &argv);

  MPI_Comm_size(MPI_COMM_WORLD, &size);
  MPI_Comm_rank(MPI_COMM_WORLD, &rank);

  gethostname(hostname, len);

  printf("Hi, I am %d of %d and my hostname is %s\n", rank, size, hostname);

  MPI_Finalize();

}

OpenMP example

#include <math.h>
#include <stdio.h>

#define N 16384
#define M 10

double dotproduct(int, double *);


double dotproduct(int i, double *x) {
  
  double temp=0.0, denom;
  int j;

  for (j=0; j<N; j++) {
    // zero based!!
    denom = (i+j)*(i+j+1)/2 + i+1;
    temp = temp + x[j]*(1/denom);  
  }

  return temp;
}


int main() {


  double *x = new double[N];
  double *y = new double[N];
  double eig = sqrt(N);
  double denom,temp;
  int i,j,k;

  for (i=0; i<N; i++) {
    x[i] = 1/eig;
  }

  for (k=0;k<M;k++) {

    y[i]=0;

    // compute y = Ax
#pragma omp parallel for shared(y)
    for (i=0; i<N; i++) {     
      y[i] = dotproduct(i,x);
    }
    
    // find largest eigenvalue of y
    eig = 0;    
    for (i=0; i<N; i++) {
      eig = eig + y[i]*y[i];
    }    
    eig = sqrt(eig);
   
    printf("The largest eigenvalue after %2d iteration is %16.15e\n",k+1, eig);


    // normalize
    for (i=0; i<N; i++) {
      x[i] = y[i]/eig;
    }

  }



}