2013/6/24 Tobias Pietzsch <pietz...@mpi-cbg.de> > > > First regarding the slow (feel free to skip to this paragraph...). I > played with unsigned short to ARGB conversion and noticed that it divides > by scale factor for every pixel. > I thought that maybe we could speed it up a little by replacing that with > a multiplication. Amazingly even in a language as Java that is seemingly > far removed from the CPU this actually matters. >
Just wanted to point out that this particular surprise with division, in Java, I've run into before. Another aspect of it: for whatever reason the compiler or JIT are unable to map divisions by powers of two to a bit shift. For example: int d = 16; int a = 4096 / d; ... is about substantially slower (15 to 50%) than: int s = 4; int a = 4096 >> s; ... to the same result. Albert http://albert.rierol.net http://www.ini.uzh.ch/~acardona/
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