On Sep 23, 2010, at 9:46 PM, John Clements wrote: > > On Sep 23, 2010, at 8:16 PM, Matthew Flatt wrote: > >> One more thought: Do you get to pick whether you use 16-bit integers or >> 64-bit floating-point numbers? The `flvector-' and `f64vector-' >> operations are inlined by the JIT and recognized for unboxing, so using >> flonum vectors and operations could be much faster than using raw >> pointers and 16-bit integers. > > Well, that's an option, albeit a somewhat unappetizing one; as the 44100 in > my code no doubt signaled, I'm reading and writing sound data here, and both > 16-bit ints and 32-bit floats are fairly common. 64-bit floats will be > another factor of 2 in memory, for a total of 42 megabytes per minute. > > I ran some tests, using flvectors and unsafe operations everywhere. (Code > below.)
Update before going to bed; re-running the C tests with doubles everywhere and the same setup (simply adding together two big buffers) took about half a second, so in fact in this instance Racket is less that 10x slower, which is as fast as I would expect it to be. So basically, it sounds like the flvectors are the way to go, if I can stomach the memory usage. Thanks again, John
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