allow empty string for transfer_model_from parameter, allow l2reweigh…

…t_dof=0

pfb/operators/gridder.py

@@ -608,12 +608,10 @@ def image_data_products(uvw,
         ressq = (residual_vis*residual_vis.conj()).real
         wcount = mask.sum()
         if wcount:
-            ovar = ressq.sum()/wcount
-            l2wgt = (l2reweight_dof + 1)/(l2reweight_dof + ressq/ovar)/ovar
+            ovar = ressq.sum()/wcount  # use 67% quantile?
+            wgt = (l2reweight_dof + 1)/(l2reweight_dof + ressq/ovar)/ovar
         else:
-            l2wgt = None
-    else:
-        l2wgt = None
+            wgt = None
 
 
     # we usually want to re-evaluate this since the robustness may change
@@ -628,16 +626,7 @@ def image_data_products(uvw,
             nx, ny,
             cellx, celly,
             robustness)
-
-        # this is necessitated by the way the weighting is done i.e.
-        # wgt applied to vis@init so only imwgt*l2wgt needs to be applied
-        if l2wgt is not None:
-            imwgt *= l2wgt
-
-        # wgt*imwgt*l2wgt required for PSF
         wgt *= imwgt
-    else:
-        imwgt = None
 
     if do_weight:
         out_dict['WEIGHT'] = wgt
@@ -650,7 +639,6 @@ def image_data_products(uvw,
         freq=freq,
         vis=vis,
         wgt=wgt,
-        # wgt=imwgt,  # data already naturally weighted
         mask=mask,
         npix_x=nx, npix_y=ny,
         pixsize_x=cellx, pixsize_y=celly,

pfb/workers/grid.py

@@ -291,7 +291,7 @@ def _grid(xdsi=None, **kw):
         print(f'Image space data products will be stored in {dds_name}.', file=log)
 
     # check if model exists
-    if opts.transfer_model_from is not None:
+    if opts.transfer_model_from:
         try:
             mds = xds_from_zarr(opts.transfer_model_from,
                                 chunks={'params':-1, 'comps':-1})[0]
@@ -399,7 +399,7 @@ def _grid(xdsi=None, **kw):
         out_ds = out_ds.assign(**{'BEAM': (('x', 'y'), bvals)})
 
         # get the model
-        if opts.transfer_model_from is not None:
+        if opts.transfer_model_from:
             from pfb.utils.misc import eval_coeffs_to_slice
             model = eval_coeffs_to_slice(
                 ds.time_out,