explicitly resize_thread_pool in gridding workers

pfb/operators/gridder.py

@@ -12,6 +12,7 @@
 import dask.array as da
 from ducc0.wgridder.experimental import vis2dirty, dirty2vis
 from ducc0.fft import c2r, r2c, c2c
+from ducc0.misc import resize_thread_pool
 from africanus.constants import c as lightspeed
 from pfb.utils.weighting import counts_to_weights, _compute_counts
 from pfb.utils.beam import eval_beam
@@ -339,7 +340,7 @@ def image_data_products(dsl,
     Assumes all datasets are concatenatable and will compute weighted
     sum of beam
     '''
-
+    resize_thread_pool(nthreads)
     flip_u, flip_v, flip_w, x0, y0 = wgridder_conventions(l0, m0)
 
     # TODO - assign ug,vg-coordinates
@@ -679,6 +680,7 @@ def compute_residual(dsl,
     '''
     Function to compute residual and write it to disk
     '''
+    resize_thread_pool(nthreads)
     # expects a list
     if isinstance(dsl, str):
         dsl = [dsl]