[6.40] [RF] Speed up CodegenContext::beginLoop() with single graph traversal - #23326
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guitargeek merged 1 commit intoSep 9, 2026
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To figure out which vector observables to loop over, beginLoop() called RooAbsArg::dependsOn() once per vector observable. These dependsOn() walks don't deduplicate visited nodes, so their cost scales with the number of paths in the computation graph instead of the number of nodes, which gets very expensive for large models with many shared nodes. Replace the per-observable walks with a single depth-first traversal that visits every node only once and collects the reachable vector observables, which is equivalent. For the ATLAS VHbb benchmark workspace from rootbench, this reduces the "Function JIT time" of the codegen backend (which includes the code generation itself) from 9.4 s to 5.3 s. 🤖 Done with the help of AI (cherry picked from commit 76babf1)
Test Results 22 files 22 suites 3d 11h 10m 7s ⏱️ Results for commit 2f76bed. |
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Backport of #23313, requested by @guitargeek.