sprinkle in some dels

Author: kandersolar

pvlib/bifacial/utils.py

@@ -128,6 +128,12 @@ def _vf_ground_sky_2d(x, rotation, gcr, pitch, height, max_rows=10):
         is the starting angle of each wedge, ``wedge_angles[1,:,:,:]`` is the
         end angle. [degree]
     """
+    # This function creates large float64 arrays of size
+    # (2*len(x)*len(rotation)*len(max_rows)) or ~100 MB for
+    # typical time series inputs.  This function uses `del` to
+    # allow python to recapture intermediate variables and
+    # reduce peak memory usage.
+
     # handle floats:
     x = np.atleast_1d(x)[:, np.newaxis, np.newaxis]
     rotation = np.atleast_1d(rotation)[np.newaxis, :, np.newaxis]
@@ -136,19 +142,30 @@ def _vf_ground_sky_2d(x, rotation, gcr, pitch, height, max_rows=10):
     distance_to_row_centers = (all_k - x) * pitch
     dy = width * sind(rotation)
     dx = width * cosd(rotation)
+
     # angles from x to right edge of each row
     a1 = height + dy
     b1 = distance_to_row_centers + dx
     phi_1 = np.arctan2(a1, b1)  # dimensions: (x, rotation, row)
+    del a1, b1  # reduce max memory usage
+
     # angles from x to left edge of each row
     a2 = height - dy
     b2 = distance_to_row_centers - dx
     phi_2 = np.arctan2(a2, b2)  # dimensions: (x, rotation, row)
+    del a2, b2  # reduce max memory usage
+
     phi = np.stack([phi_1, phi_2])  # dimensions: (row edge, x, rotation, row)
     swap = phi_1 > phi_2
+    del phi_1, phi_2  # reduce max memory usage
+
     # swap where phi_1 > phi_2 so that phi[0,:,:,:] is the lesser angle
     phi = np.where(swap, phi[::-1], phi)
+    del swap  # reduce max memory usage
+
     # right edge of next row - left edge of previous row
     wedge_vfs = 0.5 * (np.cos(phi[1, :, :, 1:]) - np.cos(phi[0, :, :, :-1]))
     vf = np.sum(np.clip(wedge_vfs, a_min=0., a_max=None), axis=-1)
+    del wedge_vfs  # reduce max memory usage
+
     return vf, np.degrees(phi)