[RF] Let RooGenericPdf/RooFormulaVar declare a piecewise-flat binning#22708
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A RooGenericPdf or RooFormulaVar that is constant within bins of an
observable (a step function) was always integrated with the generic
adaptive numeric integrator, which is needlessly expensive: for a flat
distribution the integral is just the sum of each bin's value times its
width.
Add RooGenericPdf::setBinning() and RooFormulaVar::setBinning(),
which take a RooAbsBinning for an observable and declare the function to be
flat within those bins. Once set:
* isBinnedDistribution() reports the observable as binned, so
RooRealIntegral selects the fast RooBinIntegrator;
* binBoundaries() and plotSamplingHint() expose the bins so that
integration covers exactly the range and plotting draws crisp steps.
A binning can be registered for several observables (e.g. for a
multi-dimensional flat distribution). By default the function is sampled
inside each bin to verify that it really is flat, and the binning is
rejected with an error otherwise; pass checkFlatness=false to skip this.
The binnings are stored in a std::map keyed by the observable's index in
the internal variable list, so they survive renaming of a variable or a
server redirection, and a RooUniformBinning keeps the storage compact even
for many bins. Lookups resolve the observable by name, so a same-named
stand-in (e.g. one read back separately from a file) is accepted too.
The shared flatness check and bin-boundary helpers live in RooHelpers.
The persistent schema version of both classes is bumped to 2.
dpiparo
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Jul 16, 2026
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thanks, looks good! |
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/backport to 6.40 |
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Preparing to backport PR #22708 to branch 6.40 requested by guitargeek |
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Something went wrong when assigning the PR or setting labels @guitargeek please see the logs |
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This PR has been backported to branch 6.40: #22838 |
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A RooGenericPdf or RooFormulaVar that is constant within bins of an
observable (a step function) was always integrated with the generic
adaptive numeric integrator, which is needlessly expensive: for a flat
distribution the integral is just the sum of each bin's value times its
width.
Add RooGenericPdf::setBinning() and RooFormulaVar::setBinning(),
which take a RooAbsBinning for an observable and declare the function to be
flat within those bins. Once set:
RooRealIntegral selects the fast RooBinIntegrator;
integration covers exactly the range and plotting draws crisp steps.
A binning can be registered for several observables (e.g. for a
multi-dimensional flat distribution). By default the function is sampled
inside each bin to verify that it really is flat, and the binning is
rejected with an error otherwise; pass checkFlatness=false to skip this.
The binnings are stored in a std::map keyed by the observable's index in
the internal variable list, so they survive renaming of a variable or a
server redirection, and a RooUniformBinning keeps the storage compact even
for many bins. Lookups resolve the observable by name, so a same-named
stand-in (e.g. one read back separately from a file) is accepted too.
The shared flatness check and bin-boundary helpers live in RooHelpers.
The persistent schema version of both classes is bumped to 2.