off by one error in poisson_grid_fill

From: Andrew Dawson <dawson_at_nyahnyahspammersnyahnyah>
Date: Wed May 29 2013 - 13:20:32 MDT

I think there is a small error in the source for the subroutine poisxy2,
which is called by poisson_grid_fill. The error is only present for cyclic
grids.

Line 118 of fill_msg_grid.f reads:

    if (i.eq.1 .and. gtype.eq.1) im1 = il-1

I think this should be:

    if (i.eq.1 .and. gtype.eq.1) im1 = il

When determining the longitude points contributing to the Laplacian of a
point on the left-most edge of a cyclic grid, the correct points are the
right-most point at the same latitude and the point to the right of the
current one. The code as it stands uses the second right-most value instead
of the right-most value, probably just a typing error. I hope that makes
sense!

I'm currently using a binary version of NCL, will I have to compile the
whole of NCL from source to use this fix?

Thanks,
Andrew

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Received on Wed May 29 13:20:44 2013

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