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bpo-41513: Improve order of adding fractional values. Improve variable names. (GH-22368)

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Raymond Hettinger 2020-09-22 20:01:12 -07:00 committed by GitHub
parent d986d1657e
commit 438e9fc66f
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1 changed files with 12 additions and 12 deletions
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Modules/mathmodule.c
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@ -2503,7 +2503,7 @@ static inline double
vector_norm(Py_ssize_t n, double *vec, double max, int found_nan) vector_norm(Py_ssize_t n, double *vec, double max, int found_nan)
{ {
const double T27 = 134217729.0; /* ldexp(1.0, 27) + 1.0) */ const double T27 = 134217729.0; /* ldexp(1.0, 27) + 1.0) */
double x, csum = 1.0, oldcsum, scale, frac=0.0, frac_mid=0.0, frac_lo=0.0; double x, scale, oldcsum, csum = 1.0, frac1 = 0.0, frac2 = 0.0, frac3 = 0.0;
double t, hi, lo, h; double t, hi, lo, h;
int max_e; int max_e;
Py_ssize_t i; Py_ssize_t i;
@ -2539,18 +2539,18 @@ vector_norm(Py_ssize_t n, double *vec, double max, int found_nan)
assert(fabs(csum) >= fabs(x)); assert(fabs(csum) >= fabs(x));
oldcsum = csum; oldcsum = csum;
csum += x; csum += x;
frac += (oldcsum - csum) + x; frac1 += (oldcsum - csum) + x;
x = 2.0 * hi * lo; x = 2.0 * hi * lo;
assert(fabs(csum) >= fabs(x)); assert(fabs(csum) >= fabs(x));
oldcsum = csum; oldcsum = csum;
csum += x; csum += x;
frac_mid += (oldcsum - csum) + x; frac2 += (oldcsum - csum) + x;
assert(csum + lo * lo == csum); assert(csum + lo * lo == csum);
frac_lo += lo * lo; frac3 += lo * lo;
} }
h = sqrt(csum - 1.0 + (frac_lo + frac_mid + frac)); h = sqrt(csum - 1.0 + (frac1 + frac2 + frac3));
x = h; x = h;
t = x * T27; t = x * T27;
@ -2562,21 +2562,21 @@ vector_norm(Py_ssize_t n, double *vec, double max, int found_nan)
assert(fabs(csum) >= fabs(x)); assert(fabs(csum) >= fabs(x));
oldcsum = csum; oldcsum = csum;
csum += x; csum += x;
frac += (oldcsum - csum) + x; frac1 += (oldcsum - csum) + x;
x = -2.0 * hi * lo; x = -2.0 * hi * lo;
assert(fabs(csum) >= fabs(x)); assert(fabs(csum) >= fabs(x));
oldcsum = csum; oldcsum = csum;
csum += x; csum += x;
frac_mid += (oldcsum - csum) + x; frac2 += (oldcsum - csum) + x;
x = -lo * lo; x = -lo * lo;
assert(fabs(csum) >= fabs(x)); assert(fabs(csum) >= fabs(x));
oldcsum = csum; oldcsum = csum;
csum += x; csum += x;
frac_lo += (oldcsum - csum) + x; frac3 += (oldcsum - csum) + x;
x = csum - 1.0 + (frac_lo + frac_mid + frac); x = csum - 1.0 + (frac1 + frac2 + frac3);
return (h + x / (2.0 * h)) / scale; return (h + x / (2.0 * h)) / scale;
} }
/* When max_e < -1023, ldexp(1.0, -max_e) overflows. /* When max_e < -1023, ldexp(1.0, -max_e) overflows.
@ -2591,9 +2591,9 @@ vector_norm(Py_ssize_t n, double *vec, double max, int found_nan)
assert(fabs(csum) >= fabs(x)); assert(fabs(csum) >= fabs(x));
oldcsum = csum; oldcsum = csum;
csum += x; csum += x;
frac += (oldcsum - csum) + x; frac1 += (oldcsum - csum) + x;
} }
return max * sqrt(csum - 1.0 + frac); return max * sqrt(csum - 1.0 + frac1);
} }
#define NUM_STACK_ELEMS 16 #define NUM_STACK_ELEMS 16