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A rational writes its decimal out again in a precision other than the one it kept - #1869
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Rafael-SOWNet merged 3 commits intoOct 13, 2026
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… one it kept Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_012sonx8iAspMiwRwokT1Ura
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Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_012sonx8iAspMiwRwokT1Ura
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Fixes #1868.
Rational.EDecimalwas written out once, in the precision current the first time it was read, and kept from then on. Under a higherDecimalPrecisionContextthe rational still answered about a hundred digits, and so did every value computed from it. The integrator checks its answers at the default precision, so every rational in an antiderivative was affected: differentiating a right answer back at 300 or 2,000 digits left the same1e-102residual at both precisions. mpmath agrees with the answer to1e-322.The cache now holds the context it was written in and is written again under any other context. It is keyed by context instance, as the library's constant cache is. The holder is a struct equal to every other, like the caches on
Entity, so two equal rationals stay equal whichever one has been written out.Rational.Create(128, 12167).EDecimalread at the default precision, then under 300 digitssqrt(46) * 128/12167under 300 digits, with that rational4.7e-1014.1e-1012.5.0 wrote the decimal out when the rational was made, and master when it was first read; both kept it.
The new test in
HighPrecisionFunctionsTest, next to the same test fore(#1367), fails on master and passes here.Rubi corpus (pocket of all of 1.2.1.5, plus every family): identical on both arms, 0 moves and 0 wrong, as a precision fix should be. The allocation gate passed. The suite passed: 15,303 passed, 0 failed. Master 7ca5b88 is merged in, and the build passes for every target framework.
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