Keep signed photon weights in Sum._shoot (#1352) - #1364
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After each component _shoot, Sum was assigning fluxPerPhoton from the unsigned (positive+negative) weight. ChromaticSum already keeps the component fluxes, which OpticalPSF InterpolatedImage needs because of ringing. Fixes GalSim-developers#1352. Co-authored-by: Cursor <cursoragent@cursor.com>
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Fixes #1352.
Sum._shootassigns each photon to a component, calls that component's_shoot, then overwritestemp.fluxwith the unsigned weight(positive_flux + negative_flux) / n.ChromaticSum._shootalready copies the component array without that assignment.That overwrite is an identity for profiles with
negative_flux = 0(Gaussian, Moffat).OpticalPSFis anInterpolatedImagewith ringing, sopositive_flux + negative_fluxis larger thanflux(here 1.584 on GalSim 2.8.5, Roman J129). Used as aphoton_opsPSF, the unsigned overwrite inflates the drawn flux.Labeled check on GalSim 2.8.5, Roman J129,
n_photons=1000,nx=51,poisson_flux=False, seed 42,Add([OpticalPSF, OpticalPSF])/2:Sum(current)ChromaticSumofChromaticOpticalPSFA Gaussian
Sumdrawn as the object (method='phot') stays flux-faithful with or without the line (0.955 vs 0.956 on a 33² stamp). Existing Gaussiando_shootcoverage should keep passing.This is a software routing identity with
ChromaticSum, not a claim about telescope optics.AI: a compiled language model drafted the one-line dest (0 gradient-descent training steps). I reviewed the source sibling and the flux lattice before opening this PR.