3 Commits

Author	SHA1	Message	Date
Yoctopuce dev	dbbaa959c8	py/formatfloat: Improve accuracy of float formatting code. ... Following discussions in PR #16666, this commit updates the float formatting code to improve the `repr` reversibility, i.e. the percentage of valid floating point numbers that do parse back to the same number when formatted by `repr` (in CPython it's 100%). This new code offers a choice of 3 float conversion methods, depending on the desired tradeoff between code size and conversion precision: - BASIC method is the smallest code footprint - APPROX method uses an iterative method to approximate the exact representation, which is a bit slower but but does not have a big impact on code size. It provides `repr` reversibility on >99.8% of the cases in double precision, and on >98.5% in single precision (except with REPR_C, where reversibility is 100% as the last two bits are not taken into account). - EXACT method uses higher-precision floats during conversion, which provides perfect results but has a higher impact on code size. It is faster than APPROX method, and faster than the CPython equivalent implementation. It is however not available on all compilers when using FLOAT_IMPL_DOUBLE. Here is the table comparing the impact of the three conversion methods on code footprint on PYBV10 (using single-precision floats) and reversibility rate for both single-precision and double-precision floats. The table includes current situation as a baseline for the comparison: PYBV10 REPR_C FLOAT DOUBLE current = 364688 12.9% 27.6% 37.9% basic = 364812 85.6% 60.5% 85.7% approx = 365080 100.0% 98.5% 99.8% exact = 366408 100.0% 100.0% 100.0% Signed-off-by: Yoctopuce dev <dev@yoctopuce.com>	2025-08-01 00:47:33 +10:00
Damien George	3695211576	tests/float/float_format_ints.py: Put power-of-10 test in separate file. ... This test doesn't pass on builds with 30-bit floats (object repr C). Signed-off-by: Damien George <damien@micropython.org>	2023-09-29 12:00:15 +10:00
Dan Ellis	f9cbe6bc47	py/formatfloat: Format all whole-number floats exactly. ... Formerly, py/formatfloat would print whole numbers inaccurately with nonzero digits beyond the decimal place. This resulted from its strategy of successive scaling of the argument by 0.1 which cannot be exactly represented in floating point. The change in this commit avoids scaling until the value is smaller than 1, so all whole numbers print with zero fractional part. Fixes issue #4212. Signed-off-by: Dan Ellis dan.ellis@gmail.com	2022-07-26 22:23:47 +10:00