[Boost-bugs] [Boost C++ Libraries] #8692: setting mpfr precision uses wrong precision and trashes value

Subject: [Boost-bugs] [Boost C++ Libraries] #8692: setting mpfr precision uses wrong precision and trashes value
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-06-13 15:45:42

#8692: setting mpfr precision uses wrong precision and trashes value
-------------------------------------+----------------------------
 Reporter:  claude@…                 |      Owner:  johnmaddock
     Type:  Bugs                     |     Status:  new
Milestone:  To Be Determined         |  Component:  multiprecision
  Version:  Boost Development Trunk  |   Severity:  Problem
 Keywords:                           |
-------------------------------------+----------------------------
 http://svn.boost.org/svn/boost/trunk/boost/multiprecision/mpfr.hpp

 Two bugs in boost/multiprecision/mpfr.hpp:920-923

 1. set_prec trashes the value, should use prec_round
 2. precision is converted from bits to digits10, should be from digits10
 to bits

 {{{
 void precision(unsigned digits10) BOOST_NOEXCEPT
 {
   mpfr_set_prec(this->m_data,
 multiprecision::detail::digits2_2_10((digits10)));
 }
 }}}

 should be more like

 {{{
 void precision(unsigned digits10) BOOST_NOEXCEPT
 {
   mpfr_prec_round(this->m_data,
 multiprecision::detail::digits10_2_2((digits10)), GMP_RNDN);
 }
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8692>
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