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Remove unnecessary factorial array 

kf is n! at the end of the loop, so storing the values is unnecessary.
This commit is contained in:
Siddhesh Poyarekar 2013-02-13 17:19:06 +05:30
parent 4e92d59e26
commit c2af38aa76
2 changed files with 5 additions and 10 deletions
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2
ChangeLog
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@ -1,5 +1,7 @@
2013-02-13 Siddhesh Poyarekar <siddhesh@redhat.com> 2013-02-13 Siddhesh Poyarekar <siddhesh@redhat.com>
* sysdeps/ieee754/dbl-64/mpexp.c (__mpexp): Remove NFA.
* sysdeps/ieee754/dbl-64/mpexp.c (__mpexp): Faster polynomial * sysdeps/ieee754/dbl-64/mpexp.c (__mpexp): Faster polynomial
evaluation. evaluation.

13
sysdeps/ieee754/dbl-64/mpexp.c
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@ -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 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] = static const int m1p[33] =
{ {
0, 0, 0, 0, 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! 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! = 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); __cpy (&mps, &mpt2, p);
double kf = 1.0; double kf = 1.0;
@ -145,7 +138,7 @@ __mpexp (mp_no *x, mp_no *y, int p)
__add (&mpt2, &mpk, &mpt1, p); __add (&mpt2, &mpk, &mpt1, p);
__mul (&mps, &mpt1, &mpt2, p); __mul (&mps, &mpt1, &mpt2, p);
} }
__dbl_mp (nfa[p], &mpk, p); __dbl_mp (kf, &mpk, p);
__dvd (&mpt2, &mpk, &mpt1, p); __dvd (&mpt2, &mpk, &mpt1, p);
__add (&mpone, &mpt1, &mpt2, p); __add (&mpone, &mpt1, &mpt2, p);