fast map array alternative

map_array_alternative.py

import numpy as np
from skimage.util import map_array
from time import perf_counter
from skimage.util import map_array

shape = (50,1024,1024)
total = shape[0]*shape[1]*shape[2]
NUM_LABELS=total*2
input_data = np.random.randint(NUM_LABELS,size=total).reshape(shape).astype("int64")
from_values = np.arange(NUM_LABELS)
to_values = np.arange(NUM_LABELS)+100
np.random.shuffle(to_values)

def map_array_new(label_image, label_list, predictionlist):
    plist = np.zeros(
        np.max(
        [np.max(label_image),
         np.max(predictionlist)]
        )+1)
    plist[label_list] = predictionlist

    return plist[label_image]
  
def map_array_old(label_image, label_list, predictionlist):
    return map_array(label_image, label_list, predictionlist)

  
t1 = perf_counter()
res_new = map_array_new(input_data, from_values, to_values)
t_new = perf_counter() - t1
print(t_new)


t1 = perf_counter()
res_old = map_array_old(input_data, from_values, to_values)
t_old = perf_counter() - t1
print(t_old)

print(f"Speedup {t_old/t_new}")

np.array_equal(res_new,res_old)