Parallelize pixelize_sph_kernel_* methods. Fixes yt-project#2682

yt/utilities/lib/pixelization_routines.pyx

@@ -1026,13 +1026,14 @@ def pixelize_sph_kernel_projection(
             ih_j2 = 1.0/h_j2
 
             prefactor_j = pmass[j] / pdens[j] / hsml[j]**2
+
             if weight_field is None:
                 prefactor_j *= quantity_to_smooth[j]
             else:
                 prefactor_j *= quantity_to_smooth[j] * _weight_field[j]
 
             # found pixels we deposit on, loop through those pixels
-            for xi in range(x0, x1):
+            for xi in prange(x0, x1, schedule="static"):
                 # we use the centre of the pixel to calculate contribution
                 x = (xi + 0.5) * dx + x_min
 
@@ -1056,6 +1057,7 @@ def pixelize_sph_kernel_projection(
                     # now we just use the kernel projection
                     buff[xi, yi] +=  prefactor_j * itab.interpolate(q_ij2)
 
+
 @cython.boundscheck(False)
 @cython.wraparound(False)
 def interpolate_sph_positions_gather(np.float64_t[:] buff,
@@ -1279,7 +1281,7 @@ def pixelize_sph_kernel_slice(
 
             # Now we know which pixels to deposit onto for this particle,
             # so loop over them and add this particle's contribution
-            for xi in range(x0, x1):
+            for xi in prange(x0, x1, schedule="static"):
                 x = (xi + 0.5) * dx + x_min
 
                 posx_diff = posx[j] - x
@@ -1371,7 +1373,7 @@ def pixelize_sph_kernel_arbitrary_grid(np.float64_t[:, :, :] buff,
 
             # Now we know which voxels to deposit onto for this particle,
             # so loop over them and add this particle's contribution
-            for xi in range(x0, x1):
+            for xi in range(x0, x1, schedule="static"):
                 x = (xi + 0.5) * dx + x_min
 
                 posx_diff = posx[j] - x