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| author | Raymond Hettinger <rhettinger@users.noreply.github.com> | 2020-09-19 00:57:28 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-09-19 00:57:28 (GMT) |
| commit | ec8a15b034124f3b58d1addda789fa4c20313006 (patch) | |
| tree | 1905da0b22010602db49bac20141ca9f0d6f5e63 | |
| parent | 8394500cca56490cc347604d39ca40abcdce46c3 (diff) | |
| download | cpython-ec8a15b034124f3b58d1addda789fa4c20313006.zip cpython-ec8a15b034124f3b58d1addda789fa4c20313006.tar.gz cpython-ec8a15b034124f3b58d1addda789fa4c20313006.tar.bz2 | |
Make fractional value accumulation consistent inside and outside the loop. (GH-22315)
| -rw-r--r-- | Modules/mathmodule.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c index ecd291e..935759e 100644 --- a/Modules/mathmodule.c +++ b/Modules/mathmodule.c @@ -2550,8 +2550,7 @@ vector_norm(Py_ssize_t n, double *vec, double max, int found_nan) assert(csum + lo * lo == csum); frac_lo += lo * lo; } - frac += frac_lo + frac_mid; - h = sqrt(csum - 1.0 + frac); + h = sqrt(csum - 1.0 + (frac_lo + frac_mid + frac)); x = h; t = x * T27; @@ -2569,15 +2568,15 @@ vector_norm(Py_ssize_t n, double *vec, double max, int found_nan) assert(fabs(csum) >= fabs(x)); oldcsum = csum; csum += x; - frac += (oldcsum - csum) + x; + frac_mid += (oldcsum - csum) + x; x = -lo * lo; assert(fabs(csum) >= fabs(x)); oldcsum = csum; csum += x; - frac += (oldcsum - csum) + x; + frac_lo += (oldcsum - csum) + x; - x = csum - 1.0 + frac; + x = csum - 1.0 + (frac_lo + frac_mid + frac); return (h + x / (2.0 * h)) / scale; } /* When max_e < -1023, ldexp(1.0, -max_e) overflows. |