Comment (by Erik Schnetter):

I see this code:

  for (iy = 0; iy <= ny; iy++)
    for (ix = 0; ix <= nx; ix++)
      integrand_sum += f[idx(ix,iy)];

This double-counts the first/last point on the equator.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2282/gallery-examples-use-low-order-integration