Thanks for your explanation, Einar. Michal On 20 November 2011 17:24, Einar Rünkaru <eina...@smail.ee> wrote: > On Sun, Nov 20, 2011 at 3:53 PM, Michal Fapso <michal.fa...@gmail.com> wrote: >> Hi Hannes, I am really confused now. I tried to isolate the problem, >> so I created a small C test program (it is attached to this mail). It >> simulates the interpolation between frames 0 and 71 for only 2 frames >> (#2 which works fine and #3 which shows the rounding error). The main >> problem seems to come from this: >> >> double next_scale_prev_scale = next_scale * prev_scale; >> >> ...but then, interestingly (next_scale_prev_scale != next_scale * >> prev_scale). Can someone explain that? Maybe I am missing something >> obvious here. >> > Floating point calculation is not exact. This means if you try to > compare to fp variables the result of == and != is not what you > expect. If you use exact comparision in a program it is a bug. > > Regarding > ext_scale_prev_scale != next_scale * prev_scale: > > FP processor calculates some bits more, than stored in memory. The > exessive bits are thown away while storing. Immediatly after > mutiplication there are some bits more than in result stored somwhere. > If these bits are not zero the memory variant is not equal to just > calculated result. > > Einar > > _______________________________________________ > Cinelerra mailing list > Cinelerra@skolelinux.no > https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra >
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