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# benchmark reads and writes, with and without compression.
# tests all four supported file formats.
from typing import Literal
from numpy.random.mtrand import uniform
import netCDF4
from timeit import Timer
import os, sys
# use real data.
URL="http://www.esrl.noaa.gov/psd/thredds/dodsC/Datasets/ncep.reanalysis/pressure/hgt.1990.nc"
nc = netCDF4.Dataset(URL)
# use real 500 hPa geopotential height data.
n1dim = 100
n3dim = 73
n4dim = 144
ntrials = 10
sys.stdout.write('reading and writing a %s by %s by %s random array ..\n'%(n1dim,n3dim,n4dim))
sys.stdout.write('(average of %s trials)\n\n' % ntrials)
array = nc.variables['hgt'][0:n1dim,5,:,:]
def write_netcdf(
filename,
nsd,
quantize_mode: Literal["BitGroom", "BitRound", "GranularBitRound"] = "BitGroom"
):
file = netCDF4.Dataset(filename,'w',format='NETCDF4')
file.createDimension('n1', None)
file.createDimension('n3', n3dim)
file.createDimension('n4', n4dim)
foo = file.createVariable('data',\
'f4',('n1','n3','n4'),\
zlib=True,shuffle=True,\
quantize_mode=quantize_mode,\
significant_digits=nsd)
foo[:] = array
file.close()
def read_netcdf(filename):
file = netCDF4.Dataset(filename)
data = file.variables['data'][:]
file.close()
for sigdigits in range(1,5,1):
sys.stdout.write('testing compression with significant_digits=%s...\n' %\
sigdigits)
write_netcdf('test.nc',sigdigits)
read_netcdf('test.nc')
# print out size of resulting files with standard quantization.
sys.stdout.write('size of test.nc = %s\n'%repr(os.stat('test.nc').st_size))
sys.stdout.write("testing compression with significant_digits=%s and 'GranularBitRound'...\n" %\
sigdigits)
write_netcdf('test.nc',sigdigits,quantize_mode='GranularBitRound')
read_netcdf('test.nc')
# print out size of resulting files with alternate quantization.
sys.stdout.write('size of test.nc = %s\n'%repr(os.stat('test.nc').st_size))
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