Comparison of ncdump vs numpy for comparing datasets

ncdump_numpy_test.py

#!/usr/bin/python2
import os
import sys
import time
import numpy as np
import subprocess
import matplotlib.pyplot as plt
from netCDF4 import Dataset

# Method one, just use numpy
var_name = "thk"
start = time.time()
test = Dataset("dome.0496.p256.out.hopper.nc","r", format='NETCDF4')
bench = Dataset("dome.0496.p256.out.titan.nc","r", format='NETCDF4')

test_thk = np.array(test.variables[var_name][:], dtype="float64")
bench_thk = np.array(bench.variables[var_name][:], dtype="float64")

diff = np.ndarray.flatten(test_thk - bench_thk)

if diff.any():
    test_thk
    print("  Numpy DataType : " + str(diff.dtype))
    print("    Size of data : " + str(diff.size))
    print("Total difference : " + str(np.sum(diff)))
    print("  Max difference : " + str(np.amax(np.absolute(diff))))
else:
    print("no change")

test.close()
bench.close()
print("   Method 1 took : " + str(time.time() - start) + " seconds")
print("")

# Method two, use ncdiff
start = time.time()
test = "dome.0496.p256.out.hopper.nc"
bench = "dome.0496.p256.out.titan.nc"

comline = ['ncdiff', '-v', 'thk,velnorm', test, bench, 'temp.nc', '-O']
try:
    subprocess.check_call(comline)
except Exception as e:
    print(str(e)+ ", File: "+ str(os.path.split(sys.exc_info()[2].tb_frame.f_code.co_filename)[1]))
    exit(1)

diff = Dataset("temp.nc",'r', format='NETCDF4')
thk = np.ndarray.flatten(diff.variables[var_name][:])

if thk.any():
    print("  Numpy DataType : " + str(diff.variables[var_name].dtype))
    print("    Size of data : " + str(thk.size))
    print("Total difference : " + str(np.sum(thk)))
    print("  Max difference : " + str(np.amax(np.absolute(thk))))
else:
    print("no change")

diff.close()
os.remove("temp.nc")
print("   Method 2 took : " + str(time.time() - start) + " seconds")