From 7148a38f948f3c6a1af855601e51862f1bd81eac Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <raymond.hettinger@gmail.com>
Date: Mon, 21 Sep 2020 00:14:51 -0700
Subject: [PATCH] Improve order of adding fractional values. Improve variable
names.
---
Modules/mathmodule.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 935759ec671ca5..5cd31b7dd4acfb 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -2502,8 +2502,8 @@ exactly equal) was verified for 1 billion random inputs with n=5. [7]
static inline double
vector_norm(Py_ssize_t n, double *vec, double max, int found_nan)
{
- 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;
+ const double T27 = 134217729.0; /* ldexp(1.0, 27) + 1.0) */
+ double x, scale, oldcsum, csum = 1.0, frac1 = 0.0, frac2 = 0.0, frac3 = 0.0;
double t, hi, lo, h;
int max_e;
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));
oldcsum = csum;
csum += x;
- frac += (oldcsum - csum) + x;
+ frac1 += (oldcsum - csum) + x;
x = 2.0 * hi * lo;
assert(fabs(csum) >= fabs(x));
oldcsum = csum;
csum += x;
- frac_mid += (oldcsum - csum) + x;
+ frac2 += (oldcsum - csum) + x;
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;
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));
oldcsum = csum;
csum += x;
- frac += (oldcsum - csum) + x;
+ frac1 += (oldcsum - csum) + x;
x = -2.0 * hi * lo;
assert(fabs(csum) >= fabs(x));
oldcsum = csum;
csum += x;
- frac_mid += (oldcsum - csum) + x;
+ frac2 += (oldcsum - csum) + x;
x = -lo * lo;
assert(fabs(csum) >= fabs(x));
oldcsum = csum;
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;
}
/* 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));
oldcsum = csum;
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