Module: ppl/ppl Branch: master Commit: b98bfa9b31c0861653c862e025372ccf5f44ae21 URL: http://www.cs.unipr.it/git/gitweb.cgi?p=ppl/ppl.git;a=commit;h=b98bfa9b31c08...

Author: Abramo Bagnara abramo.bagnara@gmail.com Date: Sat Mar 28 13:59:39 2009 +0100

Documented rational sqrt precision and implemented a more precise variant for numbers < 1.

---

TODO | 2 ++ src/Init.cc | 4 ++-- src/checked_mpq.inlines.hh | 27 +++++++++++++++++---------- 3 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/TODO b/TODO index 98df6e6..0cff626 100644 --- a/TODO +++ b/TODO @@ -12,6 +12,8 @@ Enhancements for PPL 0.10.1 or later versions Enhancements for PPL 0.11 or later versions ===========================================

+- Rename set_rational_sqrt_precision_parameter to + set_irrational_precision and make it available on all interfaces. - Intervals are best instantiated with checked numbers with particular policies: review all the interfaced boxes, augment the testsuite, and update the documentation. diff --git a/src/Init.cc b/src/Init.cc index 373ed36..dce7393 100644 --- a/src/Init.cc +++ b/src/Init.cc @@ -86,8 +86,8 @@ PPL::Init::Init() { old_rounding_direction = fpu_get_rounding_direction(); fpu_set_rounding_direction(round_fpu_dir(ROUND_DIRECT)); #endif - // FIXME(0.10.1): is 3200 a magic number? - set_rational_sqrt_precision_parameter(3200); + // FIXME(0.10.1): choose a better default + set_rational_sqrt_precision_parameter(128); } }

diff --git a/src/checked_mpq.inlines.hh b/src/checked_mpq.inlines.hh index d613489..c4bfef2 100644 --- a/src/checked_mpq.inlines.hh +++ b/src/checked_mpq.inlines.hh @@ -386,16 +386,22 @@ inline Result sqrt_mpq(mpq_class& to, const mpq_class& from, Rounding_Dir dir) { if (CHECK_P(To_Policy::check_sqrt_neg, from < 0)) return assign_special<To_Policy>(to, V_SQRT_NEG, ROUND_IGNORE); - const unsigned long k = rational_sqrt_precision_parameter; - mpz_class& to_num = to.get_num(); - mul2exp<To_Policy, From_Policy>(to_num, from.get_num(), 2*k, dir); + if (from == 0) { + to = 0; + return V_EQ; + } + bool gt1 = from.get_num() > from.get_den(); + const mpz_class& from_a = gt1 ? from.get_num() : from.get_den(); + const mpz_class& from_b = gt1 ? from.get_den() : from.get_num(); + mpz_class& to_a = gt1 ? to.get_num() : to.get_den(); + mpz_class& to_b = gt1 ? to.get_den() : to.get_num(); + Rounding_Dir rdir = gt1 ? dir : inverse(dir); + mul2exp<To_Policy, From_Policy>(to_a, from_a, 2*rational_sqrt_precision_parameter, ROUND_IGNORE); Result rdiv - = div<To_Policy, To_Policy, To_Policy>(to_num, - to_num, from.get_den(), dir); - Result rsqrt = sqrt<To_Policy, To_Policy>(to_num, to_num, dir); - mpz_class& to_den = to.get_den(); - to_den = 1; - mul2exp<To_Policy, To_Policy>(to_den, to_den, k, dir); + = div<To_Policy, To_Policy, To_Policy>(to_a, to_a, from_b, rdir); + Result rsqrt = sqrt<To_Policy, To_Policy>(to_a, to_a, rdir); + to_b = 1; + mul2exp<To_Policy, To_Policy>(to_b, to_b, rational_sqrt_precision_parameter, ROUND_IGNORE); to.canonicalize(); return rdiv != V_EQ ? rdiv : rsqrt; } @@ -456,7 +462,8 @@ rational_sqrt_precision_parameter() { }

//! Sets the precision parameter used for rational square root calculations. -/*! +/*! The lesser between numerator and denominator is limited to 2**\p p. + If \p p is less than or equal to <CODE>INT_MAX</CODE>, sets the precision parameter used for rational square root calculations to \p p.