update usage

test_batch/python_cpu.py

@@ -0,0 +1,20 @@
+#!/usr/bin/env python
+
+import multiprocessing 
+import os # For reading the amount of CPUs requested. 
+import time # For clocking the calculation. 
+
+def double(data):
+    return data ** 2
+
+if __name__ == '__main__':
+    begin = time.time()
+    inputs = list(range(10000)) # Makes an array from 0 to 10
+    poolSize = int(os.environ['SLURM_JOB_CPUS_PER_NODE']) # Amount of CPUs requested.
+    pool = multiprocessing.Pool(processes=poolSize,)
+    poolResults = pool.map(double, inputs) # Do the calculation.
+    pool.close() # Stop pool accordingly.
+    pool.join()  # Wrap up data from the workers in the pool.
+    print ('Pool output:', poolResults) # Results.
+    elapsedTime = time.time() - begin
+    print ('Time elapsed for ' , poolSize, ' workers: ', elapsedTime, ' seconds')