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Fix rare bug that breaks invariants in exp.

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jzmaddock
2014-10-09 16:41:21 +01:00
parent 63f53c48f3
commit 55bbda0c31
1 changed files with 6 additions and 1 deletions
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7
include/boost/multiprecision/cpp_bin_float/transcendental.hpp
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@@ -103,7 +103,12 @@ void eval_exp(cpp_bin_float<Digits, DigitBase, Allocator, Exponent, MinE, MaxE>
eval_multiply(t, n, default_ops::get_constant_ln2<cpp_bin_float<Digits, DigitBase, Allocator, Exponent, MinE, MaxE> >());
eval_subtract(t, arg);
t.negate();
BOOST_ASSERT(t.compare(limb_type(0)) >= 0);
if(eval_get_sign(t) < 0)
{
// There are some very rare cases where arg/ln2 is an integer, and the subsequent multiply
// rounds up, in that situation t ends up negative at this point which breaks our invariants below:
t = limb_type(0);
}
BOOST_ASSERT(t.compare(default_ops::get_constant_ln2<cpp_bin_float<Digits, DigitBase, Allocator, Exponent, MinE, MaxE> >()) < 0);
Exponent k, nn;