The FFT histogram extent was written as maxQ = 2*pi/HighRes (the powder Q = 2*pi/d
convention) while the bin width and spot coordinates use the internal 1/d convention -
a unit conflation. It is benign: len_coeff = 2*max_length/histogram_size carries the
same factor, so recovered cell lengths are correct; the 2*pi only acts as a ~6.28x
zero-padding of the histogram.
Rewrite it transparently: one_over_d_max = 1/HighRes (1/d), with the 2*pi kept as an
explicitly-named oversampling factor. In this codebase Q always denotes 2*pi/d, so 1/d
is named one_over_d (never q). histogram_size is numerically identical to before, so
behaviour is unchanged (FFT de-novo crystal 2 95.44%, bit-identical merge). Documented
that the exact padding amount is load-bearing at the marginal-frame level (rounding 2*pi
to a nearby integer shifts indexing ~0.5-1%).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
leonarski_fandClaude Opus 4.8
f2f95c44f6