id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
12625	multiprecision acos() sometimes does not return	steve@…	John Maddock	"Thibaut Paumard reported the following bug to Debian as https://bugs.debian.org/844495

Some inputs cause multiprecision acos() to hang.  The following example hangs on s390x:

{{{
#include <boost/multiprecision/cpp_dec_float.hpp>

int main(int argc, char** argv) {

  boost::multiprecision::cpp_dec_float_100 alpha100, a, b;
  alpha100=5.9839860068377014046259e-02;
  b=cos(alpha100);
  a=acos(b);

  return 0;
}
}}}


Known affected architectures include arm64 armel armhf mips64el mipsel ppc64el s390x powerpc ppc64.  It's not clear to me whether the value of alpha100 needs to be adjusted to trigger the bug on different architectures.

Thibaut has proposed the attached patch.  Would appreciate knowing the maintainer's thoughts about the patch.




"	Bugs	closed	To Be Determined	multiprecision	Boost 1.62.0	Problem	fixed		steve@… thibaut@…