Comparison of ARCSI code with/without parallelisation

gistfile1.py

# Simple test of method used in current ARCSI code (old_method)
# and Py6S parallelisation (new_method)

# Results from running it on my (relatively old, dual-core) MacBook Pro:
# old_method: 21.1s
# new_method: 10.6s
# 
# We get roughly the 2x speed up that you'd expect with two cores.
# 
# Running on my work machine which has 8 cores I get:
# old_method: 11s
# new_method: 3.41s
#
# The speedup isn't anywhere near 8x (so it doesn't scale perfectly)
# but a 3x speedup isn't bad

import Py6S
s = Py6S.SixS()
s.altitudes.set_target_sea_level()
s.altitudes.set_sensor_satellite_level()
s.atmos_corr = Py6S.AtmosCorr.AtmosCorrLambertianFromRadiance(100)


def old_method():
        sixsCoeffs = numpy.zeros((6, 3), dtype=numpy.float32)   
        # Band 1
        s.wavelength = Py6S.Wavelength(Py6S.SixSHelpers.PredefinedWavelengths.LANDSAT_ETM_B1)
        s.run()
        sixsCoeffs[0,0] = float(s.outputs.values['coef_xa'])
        sixsCoeffs[0,1] = float(s.outputs.values['coef_xb'])
        sixsCoeffs[0,2] = float(s.outputs.values['coef_xc'])
        
        # Band 2
        s.wavelength = Py6S.Wavelength(Py6S.SixSHelpers.PredefinedWavelengths.LANDSAT_ETM_B2)
        s.run()
        sixsCoeffs[1,0] = float(s.outputs.values['coef_xa'])
        sixsCoeffs[1,1] = float(s.outputs.values['coef_xb'])
        sixsCoeffs[1,2] = float(s.outputs.values['coef_xc'])
        
        # Band 3
        s.wavelength = Py6S.Wavelength(Py6S.SixSHelpers.PredefinedWavelengths.LANDSAT_ETM_B3)
        s.run()
        sixsCoeffs[2,0] = float(s.outputs.values['coef_xa'])
        sixsCoeffs[2,1] = float(s.outputs.values['coef_xb'])
        sixsCoeffs[2,2] = float(s.outputs.values['coef_xc'])
        
        # Band 4
        s.wavelength = Py6S.Wavelength(Py6S.SixSHelpers.PredefinedWavelengths.LANDSAT_ETM_B4)
        s.run()
        sixsCoeffs[3,0] = float(s.outputs.values['coef_xa'])
        sixsCoeffs[3,1] = float(s.outputs.values['coef_xb'])
        sixsCoeffs[3,2] = float(s.outputs.values['coef_xc'])
        
        # Band 5
        s.wavelength = Py6S.Wavelength(Py6S.SixSHelpers.PredefinedWavelengths.LANDSAT_ETM_B5)
        s.run()
        sixsCoeffs[4,0] = float(s.outputs.values['coef_xa'])
        sixsCoeffs[4,1] = float(s.outputs.values['coef_xb'])
        sixsCoeffs[4,2] = float(s.outputs.values['coef_xc'])
        
        # Band 7
        s.wavelength = Py6S.Wavelength(Py6S.SixSHelpers.PredefinedWavelengths.LANDSAT_ETM_B7)
        s.run()
        sixsCoeffs[5,0] = float(s.outputs.values['coef_xa'])
        sixsCoeffs[5,1] = float(s.outputs.values['coef_xb'])
        sixsCoeffs[5,2] = float(s.outputs.values['coef_xc'])
        
        return sixsCoeffs

def new_method():
        sixsCoeffs = numpy.zeros((6, 3), dtype=numpy.float32)   

        wavelengths, results = Py6S.SixSHelpers.Wavelengths.run_landsat_etm(s)
        coef_xa = [getattr(r, 'coef_xa') for r in results]
        coef_xb = [getattr(r, 'coef_xb') for r in results]
        coef_xc = [getattr(r, 'coef_xc') for r in results]

        sixsCoeffs[:, 0] = coef_xa
        sixsCoeffs[:, 1] = coef_xb
        sixsCoeffs[:, 2] = coef_xc

        return sixsCoeffs