speed up tile download with concurrent processing (#182)

* speed up tile download with concurrent proccessing

* remove time print

* make threadcount optional cli images argument

* clean up

* drop default threads down to 10

* switch to list comprehension, remove prints

* remove time import

Author: Martha Morrissey

label_maker/images.py

@@ -1,14 +1,15 @@
 # pylint: disable=unused-argument
 """Generate an .npz file containing arrays for training machine learning algorithms"""
 
+import concurrent.futures
 from os import makedirs, path as op
 from random import shuffle
 
 import numpy as np
 
 from label_maker.utils import get_image_function
 
-def download_images(dest_folder, classes, imagery, ml_type, background_ratio, imagery_offset=False, **kwargs):
+def download_images(dest_folder, classes, imagery, ml_type, background_ratio, threadcount, imagery_offset=False, **kwargs):
     """Download satellite images specified by a URL and a label.npz file
     Parameters
     ------------
@@ -28,6 +29,8 @@ def download_images(dest_folder, classes, imagery, ml_type, background_ratio, im
     background_ratio: float
         Determines the number of background images to download in single class problems. Ex. A value
         of 1 will download an equal number of background images to class images.
+    threadcount: int
+        Number of threads to use for faster parallel image download
     imagery_offset: list
         An optional list of integers representing the number of pixels to offset imagery. Ex. [15, -5] will
         move the images 15 pixels right and 5 pixels up relative to the requested tile bounds
@@ -72,5 +75,6 @@ def class_test(value):
     image_function = get_image_function(imagery)
     kwargs['imagery_offset'] = imagery_offset
 
-    for tile in tiles:
-        image_function(tile, imagery, tiles_dir, kwargs)
+    with concurrent.futures.ThreadPoolExecutor(max_workers=threadcount) as executor:
+        [executor.submit(image_function, tile, imagery, tiles_dir, kwargs) for tile in tiles]
+        executor.shutdown(wait=True)

label_maker/main.py

@@ -50,7 +50,7 @@ def parse_args(args):
     subparsers.add_parser('download', parents=[pparser], help='', formatter_class=dhf)
     l = subparsers.add_parser('labels', parents=[pparser], help='', formatter_class=dhf)
     p = subparsers.add_parser('preview', parents=[pparser], help='', formatter_class=dhf)
-    subparsers.add_parser('images', parents=[pparser], help='', formatter_class=dhf)
+    i = subparsers.add_parser('images', parents=[pparser], help='', formatter_class=dhf)
     subparsers.add_parser('package', parents=[pparser], help='', formatter_class=dhf)
 
     # labels has an optional parameter
@@ -60,6 +60,10 @@ def parse_args(args):
     p.add_argument('-n', '--number', default=5, type=int,
                    help='number of examples images to create per class')
 
+    #images has optional parameter
+    i.add_argument('-t', '--threadcount', default=10, type=int,
+                    help= 'thread count to use')
+
     # turn namespace into dictinary
     parsed_args = vars(parser.parse_args(args))
 
@@ -109,7 +113,8 @@ def cli():
         number = args.get('number')
         preview(dest_folder=dest_folder, number=number, **config)
     elif cmd == 'images':
-        download_images(dest_folder=dest_folder, **config)
+        threadcount = args.get('threadcount')
+        download_images(dest_folder=dest_folder, threadcount=threadcount, **config)
     elif cmd == 'package':
         package_directory(dest_folder=dest_folder, **config)