Avoid storing inconsistent sum/sum_sq on summed D1S tallies#3949
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For sum_nuclides=True, apply_time_correction returns a derived tally with the ParentNuclideFilter removed. The previous code left _sum/_sum_sq set to per-parent-nuclide arrays shaped for the pre-removal filter set. These are unreachable through the public Tally.sum/sum_sq accessors (which return None for any derived tally) and are inconsistent with the tally's remaining filters. Set sum/sum_sq to None for the summed result (matching the observable develop behavior, since the accessors already return None) and skip the two full-size array multiplies that are never read. mean/std_dev are unchanged bit-for-bit. This speeds up the summed path by up to ~2.8x for large mesh tallies by not computing the discarded arrays.
jon-proximafusion
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paulromano
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May 30, 2026
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LGTM. Thanks @jon-proximafusion!
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Description
I think we are doing some compute that we don't need to when working with D1S tallies.
For sum_nuclides=True, apply_time_correction returns a derived tally with the ParentNuclideFilter removed. The previous code left _sum/_sum_sq set to per-parent-nuclide arrays shaped for the pre-removal filter set. These are unreachable through the public Tally.sum/sum_sq accessors (which return None for any derived tally) and are inconsistent with the remaining filters, so converting such a tally with Tally.sparse raises a reshape error.
Set sum/sum_sq to None for the summed result (matching the observable develop behavior) and skip the two full-size array multiplies that are never read. mean/std_dev are unchanged bit-for-bit. This fixes Tally.sparse on summed D1S tallies and speeds up the summed path for large mesh tallies by not computing the discarded arrays.
Fixes # (issue)
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