------- Comment #4 from aph at gcc dot gnu dot org 2006-02-14 15:45 ------- A bit more explanation.
The problem is caused by the fact that 9007199254740994.0 + 0.9999847412109375 is carried out in extended precision, and the result is rounded to 9007199254740995. In double precision, the result of this calculation is rounded to 9007199254740994. When the extended-precision value is rounded to double for storing, it is rounded (again) to 9007199254740996. So, double rounding leads gij to return a value of d that is 2.0, whereas it should be 0.0. Note however, that the true accurate value for d, calculated at infinite precision, is 1-(2^-16). So, the absolute error for gcj is 1+(2^-16) and the absolute error with correct rounding is 1-(2^-16). (I'm not surprised this hasn't been reported as a problem with any real applications!) It might be worth setting the floating-point precision of gcj to double, but that would only fix the double-precision case, and I presume we'd still have the same double rounding problem for floats. And in any case, I do not know if libcalls would be affected by being entered with the FPU in round-to-double mode. We might end up breaking things. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16122 ------- You are receiving this mail because: ------- You reported the bug, or are watching the reporter. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
