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authorTavian Barnes <tavianator@gmail.com>2010-11-18 18:48:22 -0500
committerTavian Barnes <tavianator@gmail.com>2010-11-18 18:48:22 -0500
commit17e517be54922a848a4e79394d0969d57e5b3b9e (patch)
tree3b80b4a02bdb5209c7f9023011a90189d350f3af /libdimension
parenta69a062b31a26f04699315179ed1026d9cfedf5e (diff)
downloaddimension-17e517be54922a848a4e79394d0969d57e5b3b9e.tar.xz
A couple polynomial.c improvements.
Diffstat (limited to 'libdimension')
-rw-r--r--libdimension/polynomial.c18
1 files changed, 5 insertions, 13 deletions
diff --git a/libdimension/polynomial.c b/libdimension/polynomial.c
index 09a2bb0..0c4168d 100644
--- a/libdimension/polynomial.c
+++ b/libdimension/polynomial.c
@@ -69,17 +69,9 @@ dmnsn_eliminate_zero_roots(double poly[], size_t *degree)
static inline size_t
dmnsn_descartes_rule(const double poly[], size_t degree)
{
- int lastsign = 0;
- size_t i;
- for (i = 0; i <= degree; ++i) {
- if (fabs(poly[i]) >= dmnsn_epsilon) {
- lastsign = dmnsn_signbit(poly[i]);
- break;
- }
- }
-
size_t changes = 0;
- for (++i; i <= degree; ++i) {
+ int lastsign = dmnsn_signbit(poly[degree]);
+ for (size_t i = degree; i-- > 0;) {
int sign = dmnsn_signbit(poly[i]);
if (fabs(poly[i]) >= dmnsn_epsilon && sign != lastsign) {
lastsign = sign;
@@ -209,15 +201,15 @@ dmnsn_uspensky_bounds(const double poly[], size_t degree, double bounds[][2],
}
}
-/** Calculate a finite upper bound for the roots of \p poly[]. */
+/** Calculate a finite upper bound for the roots of the normalized polynomial
+ \p poly[]. */
static inline double
-dmnsn_root_bound(double poly[], size_t degree)
+dmnsn_root_bound(const double poly[], size_t degree)
{
double bound = 0.0;
for (size_t i = 0; i < degree; ++i) {
bound = dmnsn_max(bound, fabs(poly[i]));
}
- bound /= fabs(poly[degree]);
bound += 1.0;
return bound;
}