Exercise 3

• Log into kong.njit.edu
• cd to HPC_Workshop directory in your home directory.
• mkdir openMP
• cd to openMP
• Copy hello_omp.c to your openMP subdirectory.
• Use the commands below to display available compilers on kong
  
  1. module avail gcc
  2. module avail intel
• To invoke OpenMP, you need to use the appropriate compiler flag:
  • Compile the hello_omp.c; for gcc:
    
    $ gcc -o hello_omp -fopenmp hello_omp.c
    
    
  • and for icc
    
    $ icc -o hello_omp -qopenmp hello_omp.c
    
    
• Run the code by
  
  $ ./hello_omp
  
  and notice its output.
• How many threads were created? Why?
• Vary the number of threads by
  
  $ export OMP_NUM_THREADS=4
  
  and re-run the code.
  
  
• Re-run the code several times; can you explain why the order of output is more or less random.
• Use the OpenMP script file and submit your job to the cluster queue: https://web.njit.edu/~shahriar/class_home/HPC/omp_script.sh
• Change the number of threads and re-run your code.

____________________________________________________________