fixes (I think...)

nifty_gridder.cc

@@ -403,7 +403,7 @@ template<typename T> class Baselines
         auto t = idx(i);
         auto row = t/nchan;
         auto chan = t-row*nchan;
-        ms(row, chan) = vis(i);
+        ms(row, chan) += vis(i);
         }
       }
       return res;
@@ -681,7 +681,6 @@ template<typename T> pyarr_c<complex<T>> vis2grid_c(
   auto grid = res.mutable_data();
   {
   py::gil_scoped_release release;
-  for (size_t i=0; i<nu*nv; ++i) grid[i] = 0.;
   T beta = gconf.Beta();
   size_t w = gconf.W();
 
@@ -737,7 +736,6 @@ template<typename T> pyarr_c<complex<T>> ms2grid_c(
   auto grid = res.mutable_data();
   {
   py::gil_scoped_release release;
-  for (size_t i=0; i<nu*nv; ++i) grid[i] = 0.;
   T beta = gconf.Beta();
   size_t w = gconf.W();
 
@@ -798,7 +796,6 @@ template<typename T> pyarr_c<complex<T>> ms2grid_c_wgt(
   auto grid = res.mutable_data();
   {
   py::gil_scoped_release release;
-  for (size_t i=0; i<nu*nv; ++i) grid[i] = 0.;
   T beta = gconf.Beta();
   size_t w = gconf.W();