wip: run in process pool executor

Author: oesteban

nitransforms/resampling.py

@@ -8,6 +8,7 @@
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 """Resampling utilities."""
 
+from concurrent.futures import ProcessPoolExecutor
 from functools import partial
 from pathlib import Path
 import numpy as np
@@ -159,15 +160,12 @@ def _apply_volume(index, data, transform, targets=None):
             )
             return map_coordinates(data_t, targets)
 
-        # Order F ensures individual volumes are contiguous in memory
-        # Also matches NIfTI, making final save more efficient
-        resampled = np.zeros(
-            (len(ref_ndcoords), len(transform)), dtype=input_dtype, order="F"
-        )
-        for t in range(n_resamplings):
-            # Interpolate
-            resampled[..., t] = _apply_volume(t, data, transform, targets=targets)
-
+        with ProcessPoolExecutor(max_workers=njobs) as executor:
+            results = executor.map(
+                _apply_volume,
+                [(t, data, transform, targets) for t in range(n_resamplings)],
+            )
+            resampled = np.stack(list(results), -1)
     else:
         data = np.asanyarray(spatialimage.dataobj, dtype=input_dtype)