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Re: [PATCH] Remove unnecessary factorial array
On Wed, Feb 13, 2013 at 12:38:56PM +0100, Andreas Jaeger wrote:
> Yes, this is fine - but please change the comment "n! is pre-computed",
> it's wrong now,
>
Done, this is what I finally committed,
Thanks,
Siddhesh
diff --git a/sysdeps/ieee754/dbl-64/mpexp.c b/sysdeps/ieee754/dbl-64/mpexp.c
index 35c4e80..5b3ff04 100644
--- a/sysdeps/ieee754/dbl-64/mpexp.c
+++ b/sysdeps/ieee754/dbl-64/mpexp.c
@@ -50,14 +50,6 @@ __mpexp (mp_no *x, mp_no *y, int p)
6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 8
};
- /* Factorials for the values of np above. */
- static const double nfa[33] =
- {
- 1.0, 1.0, 1.0, 1.0, 6.0, 6.0, 24.0, 24.0, 120.0, 24.0, 24.0,
- 120.0, 120.0, 120.0, 720.0, 720.0, 720.0, 720.0, 720.0, 720.0,
- 720.0, 720.0, 720.0, 720.0, 5040.0, 5040.0, 5040.0, 5040.0,
- 40320.0, 40320.0, 40320.0, 40320.0, 40320.0
- };
static const int m1p[33] =
{
0, 0, 0, 0,
@@ -130,7 +122,8 @@ __mpexp (mp_no *x, mp_no *y, int p)
e^x = 1 + (x * n!/1! + x^2 * n!/2! + x^3 * n!/3!) / n!
= 1 + (x * (n!/1! + x * (n!/2! + x * (n!/3! + x ...)))) / n!
- n! is pre-computed and saved while k! is computed on the fly. */
+ k! is computed on the fly as KF and at the end of the polynomial loop, KF
+ is n!, which can be used directly. */
__cpy (&mps, &mpt2, p);
double kf = 1.0;
@@ -145,7 +138,7 @@ __mpexp (mp_no *x, mp_no *y, int p)
__add (&mpt2, &mpk, &mpt1, p);
__mul (&mps, &mpt1, &mpt2, p);
}
- __dbl_mp (nfa[p], &mpk, p);
+ __dbl_mp (kf, &mpk, p);
__dvd (&mpt2, &mpk, &mpt1, p);
__add (&mpone, &mpt1, &mpt2, p);