6 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
Dan Ellis	6f4d424f46	py/formatfloat: Use pow(10, e) instead of pos/neg_pow lookup tables. ... Rework the conversion of floats to decimal strings so it aligns precisely with the conversion of strings to floats in parsenum.c. This is to avoid rendering 1eX as 9.99999eX-1 etc. This is achieved by removing the power- of-10 tables and using pow() to compute the exponent directly, and that's done efficiently by first estimating the power-of-10 exponent from the power-of-2 exponent in the floating-point representation. Code size is reduced by roughly 100 to 200 bytes by this commit. Signed-off-by: Dan Ellis <dan.ellis@gmail.com>	2022-08-12 23:53:34 +10:00
David Lechner	3dc324d3f1	tests: Format all Python code with black, except tests in basics subdir. ... This adds the Python files in the tests/ directory to be formatted with ./tools/codeformat.py. The basics/ subdirectory is excluded for now so we aren't changing too much at once. In a few places `# fmt: off`/`# fmt: on` was used where the code had special formatting for readability or where the test was actually testing the specific formatting.	2020-03-30 13:21:58 +11:00
Damien George	955ee6477f	py/formatfloat: Fix case where floats could render with negative digits. ... Prior to this patch, some architectures (eg unix x86) could render floats with "negative" digits, like ")". For example, '%.23e' % 1e-80 would come out as "1.0000000000000000/)/(,*0e-80". This patch fixes the known cases.	2018-03-01 17:00:02 +11:00
Damien George	7b050fa76c	py/formatfloat: Fix case where floats could render with a ":" character. ... Prior to this patch, some architectures (eg unix x86) could render floats with a ":" character in them, eg 1e+39 would come out as ":e+38" (":" is just after "9" in ASCII so this is like 10e+38). This patch fixes some of these cases.	2018-03-01 16:02:59 +11:00
Damien George	bc12eca461	py/formatfloat: Fix rounding of %f format with edge-case FP values. ... Prior to this patch the %f formatting of some FP values could be off by up to 1, eg '%.0f' % 123 would return "122" (unix x64). Depending on the FP precision (single vs double) certain numbers would format correctly, but others wolud not. This patch should fix all cases of rounding for %f.	2018-03-01 15:51:03 +11:00