[treeplayer] Fix precision loss in TTree::Scan for 64-bit integers#22600
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guitargeek wants to merge 1 commit into
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[treeplayer] Fix precision loss in TTree::Scan for 64-bit integers#22600guitargeek wants to merge 1 commit into
guitargeek wants to merge 1 commit into
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Test Results 22 files 22 suites 3d 18h 31m 58s ⏱️ Results for commit c281308. |
jblomer
reviewed
Jun 14, 2026
| // The "long long" Scan/Draw column format is evaluated through `long double` | ||
| // (see TTreeFormula::PrintValue), so exact 64-bit integer output is only | ||
| // possible where `long double` has more mantissa bits than `double`. That is | ||
| // the case on x86-64 (80-bit, 64-bit mantissa) but not, e.g., on macOS ARM |
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Should we conversely test that the problem persists on macOS?
Perhaps (for a future PR), can we try to avoid floating point conversion at all when printing integers? For this we may want to leave the issue open.
| } redirectFile{"tree_7844_regression_redirect.txt"}; | ||
| treePlayer->SetScanRedirect(true); | ||
| treePlayer->SetScanFileName(redirectFile.fPath); | ||
| // The "lld" format without an embedded size (the size is given |
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What would be an example for a format with an embedded size? Should we test this, too?
The `"lld"` column format passed without an embedded size (e.g. via `"colsize=N col=lld"`) was not recognized as a `"long long"` modifier in **TTreeFormula::PrintValue**, so 64-bit integer branches (e.g. `ULong64_t`) were evaluated as double and rounded above 2^53. This commit fixes a off-by-one problem in the length-modifier detection to address the issue, adding also a regression test. Closes root-project#7844. 🤖 Done with the help of [Claude Code](https://claude.com/claude-code) (Claude Opus 4.8)
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The
"lld"column format passed without an embedded size (e.g. via"colsize=N col=lld") was not recognized as a"long long"modifier in TTreeFormula::PrintValue, so 64-bit integer branches (e.g.ULong64_t) were evaluated as double and rounded above 2^53.This commit fixes a off-by-one problem in the length-modifier detection to address the issue, adding also a regression test.
Closes #7844.
🤖 Done with the help of Claude Code (Claude Opus 4.8)