Module: ppl/ppl Branch: floating_point Commit: 5a827fc7a229ed6474101c2d951da3aa14c2d358 URL: http://www.cs.unipr.it/git/gitweb.cgi?p=ppl/ppl.git;a=commit;h=5a827fc7a229e...
Author: Fabio Bossi bossi@cs.unipr.it Date: Wed Jul 28 11:51:32 2010 +0200
Avoid dangerous casts when computing errors.
---
src/Float.templates.hh | 12 ++++++------ src/Linear_Form.templates.hh | 8 +++++--- 2 files changed, 11 insertions(+), 9 deletions(-)
diff --git a/src/Float.templates.hh b/src/Float.templates.hh index a784723..6b911ac 100644 --- a/src/Float.templates.hh +++ b/src/Float.templates.hh @@ -109,12 +109,12 @@ const FP_Interval_Type& compute_absolute_error(
PPL_ASSERT(to_compute != NULL);
- // FIXME: the inner cast may be dangerous. - analyzer_format omega = std::max( - static_cast<analyzer_format>(pow(f_base, - static_cast<analyzer_format>(1) - - f_exponent_bias - f_mantissa_bits)), - std::numeric_limits<analyzer_format>::denorm_min()); + // We assume that f_base is a power of 2. + analyzer_format omega; + int power = static_cast<int>(log2(f_base)) * + (1 - f_exponent_bias - f_mantissa_bits); + omega = std::max(static_cast<analyzer_format>(ldexpl(1.0, power)), + std::numeric_limits<analyzer_format>::denorm_min());
to_compute->build(i_constraint(GREATER_OR_EQUAL, -omega), i_constraint(LESS_OR_EQUAL, omega)); diff --git a/src/Linear_Form.templates.hh b/src/Linear_Form.templates.hh index fcb57c7..5bb64c0 100644 --- a/src/Linear_Form.templates.hh +++ b/src/Linear_Form.templates.hh @@ -418,9 +418,11 @@ Linear_Form<C>::relative_error( }
C error_propagator; - // FIXME: this cast may be dangerous. - analyzer_format lb = -pow(f_base, - -static_cast<analyzer_format>(f_mantissa_bits)); + // We assume that f_base is a power of 2. + int power = static_cast<int>(log2(f_base)) * + (-f_mantissa_bits); + analyzer_format lb = -static_cast<analyzer_format>(ldexpl(1.0, power)); + error_propagator.build(i_constraint(GREATER_OR_EQUAL, lb), i_constraint(LESS_OR_EQUAL, -lb));