Hi I’m writing a code in python able to perform several mapcalc operation on various rasters. I’m using GRASS 7.0.1 and Python 2.7. I’have my files stored in /home/myuser/rasters/ and they are linked to GRASS with r.external. The out put of the operation are going out of GRASS in /home/myuser/tmp/ with r.external.out.
I have written this code from the example provided in (https://grass.osgeo.org/grass70/manuals/libpython/pygrass.modules.interface.html?highlight=parallelmodulequeue#pygrass.modules.interface.module.ParallelModuleQueue) but there is no difference in terms of time between setting nproces=1 or nproces=8. How is possible? How can I achieve improvements?
The task that the code need to do is to read data from a file containing datetime and 2 coefficients k1 and k2. Than need to multiply and sum the input raster as out = input1 * k1 + input2 * k2.
The code that i have written is:
import pandas as pd
import os
import grass.script.setup as gsetup
import grass.script as g
import time
import copy
from grass.pygrass.modules import Module, ParallelModuleQueue
def main():
#set GRASS LOCATION AND MAPSET
gisbase = os.environ[‘GISBASE’] # Grass 7.0svn
gisdbase = os.path.abspath(“/home/myuser/grassData”)
location = ‘mylocation’ # Grass Location.
mapset = ‘mymapset’
gsetup.init(gisbase, gisdbase, location, mapset)
#READ INPUT DATA FOR RASTER CALC
df = pd.read_csv(‘input.csv’, sep=“;”, index_col=‘Date Time’, decimal=‘,’)
df.index = pd.to_datetime(df.index, unit=‘s’)
month={1:‘17’,2:‘47’,3:‘75’,4:‘105’,5:‘135’,6:‘162’,7:‘198’,8:‘228’,9:‘258’,10:‘288’,11:‘318’,12:‘344’}
hour={4:‘04’,5:‘05’,6:‘06’,7:‘07’,8:‘08’,9:‘09’,10:‘10’,11:‘11’,12:‘12’,13:‘13’,14:‘14’,15:‘15’,16:‘16’,17:‘17’,18:‘18’,19:‘19’,20:‘20’,21:‘21’,22:‘22’}
minute={0:‘00’,15:‘15’,30:‘30’,45:‘45’}
directory=‘/home/myuser/raster/’
tmp=‘/home/myuser/tmp/’
g.run_command(‘r.external.out’, directory=tmp, format=“GTiff”)
#MAPCALC
start_time = time.time()
mapcalc_list =
mapcalc = Module(“r.mapcalc”, overwrite=True, run_=False)
queue = ParallelModuleQueue(nprocs=8)
for dfix in df.index:
if 5<=dfix.hour<20:
input1 = ‘input1_’ + month[dfix.month] + ‘’ + hour[dfix.hour] + minute[dfix.minute]
input2 = 'input2’ + month[dfix.month] + ‘’ + hour[dfix.hour] + minute[dfix.minute]
out = ’ " ’ + str(dfix.date()) + '’ + str(dfix.time()) + ’ " ’
new_mapcalc = copy.deepcopy(mapcalc)
mapcalc_list.append(new_mapcalc)
m = new_mapcalc(expression=“%s = %s*%i+%s*%i”%(out,input1,df.ix[dfix,‘k1’],input2,df.ix[dfix,‘k2’]))
queue.put(m)
queue.wait()
print(“— %s seconds —” % (time.time() - start_time))
Best,
Lorenzo