Norman Vine wrote:
>
> Curtis L.Olson writes:
> >
> >Norman Vine writes:
> >> another problem is in simgear / sky / cloud.cxx
> >>
> >> bool SGCloudLayer::reposition( sgVec3 p, sgVec3 up, double
> >lon, double lat,
> >> double alt )
> >> {
> >> ....
> >> // now calculate update texture coordinates
> >> if ( last_lon < -900 ) {
> >> cout << "last_lon < -900" << endl;
> >> last_lon = lon;
> >> last_lat = lat;
> >> }
> >> // change if( lon - lat_lon != 0 || lat-last_lat != 0 ) to
> >> if ( fabs(lon-last_lon) > FLT_EPSILON || fabs(lat-last_lat) >
> >> FLT_EPSILON ) {
> >> ...
> >> }
> >
> >Norman, can you provide any further information as to how this change
> >eliminates problems on the windows side?
>
> when there is no change there is a floating point exception in
> calc_gc_course_dist(). I tied this with both the original and the
> optimized versions.
>
> >I understand that in general with floating point compares you want to
> >test if the absolute value of the difference is < some epsilon,
> >however, in this case I think I'm justified with my code. The current
> >code is actually:
> >
> > if ( lon != last_lon || lat != last_lat ) {
> >
>
Great! After applying that fix I'm able to run FGFS with LaRCsim again!!
> Better yet enable FPE exception reporting
>
> // I think this is correct for Linux
> [...]
I haven't tried how that affects MSVC, but if it enables floating point
error checking it's a very important addition that should be enabled
during every debug build.
I strongly vote for including that, too.
CU,
Christian
--
The idea is to die young as late as possible. -- Ashley Montague
Whoever that is/was; (c) by Douglas Adams would have been better...
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