code: def precompute(self, cache_dir=None, swath_usage=0, **kwargs):
          
          if kwargs.get('mask') is not None:
              LOG.warning("'mask' parameter has no affect during EWA "
                          "resampling")
  
          del kwargs
          source_geo_def = self.source_geo_def
          target_geo_def = self.target_geo_def
  
          if cache_dir:
              LOG.warning("'cache_dir' is not used by EWA resampling")
  
          # Satpy/PyResample don't support dynamic grids out of the box yet
          lons, lats = source_geo_def.get_lonlats()
          if isinstance(lons, xr.DataArray):
              # get dask arrays
              lons = lons.data
              lats = lats.data
          # we are remapping to a static unchanging grid/area with all of
          # its parameters specified
          chunks = (2,) + lons.chunks
          res = da.map_blocks(self._call_ll2cr, lons, lats,
                              target_geo_def, swath_usage,
                              dtype=lons.dtype, chunks=chunks, new_axis=[0])
          cols = res[0]
          rows = res[1]
  
          # save the dask arrays in the class instance cache
          # the on-disk cache will store the numpy arrays
          self.cache = {
              "rows": rows,
              "cols": cols,
          }
  
          return None
docs: Generate row and column arrays and store it for later use.