On Mon, Nov 9, 2009 at 10:09 AM, Emil Axelsson
Nice!
One of our project members has been looking at Atom, not for numerical computations, but for real-time scheduling (which Feldspar should deal with eventually).
What kind of code (in terms of efficiency) does the above description compile to?
Here's and example: module Main (main) where import Language.Atom main :: IO () main = do compile "filter" defaults design return () design :: Atom () design = atom "filter" $ do input <- float' "input" output <- float' "output" x <- iirFilter "filter" 1 [(2,3), (4,5)] (value input) output <== x -- | IIR filter implemented using direct form 2. iirFilter :: Name -> Float -> [(Float, Float)] -> E Float -> Atom (E Float) iirFilter name b0 coeffs x = do -- Create the filter taps. vs <- mapM (\ i -> float (name ++ show i) 0) [1 .. length coeffs] -- Cascade the filter taps together. mapM_ (\ (vA, vB) -> vA <== value vB) $ zip (tail vs) vs -- Calculate the input to the chain of taps. let w0 = sum ( x : [ (value v) * Const (-a) | (v, (a, _)) <- zip vs coeffs ]) bs = b0 : (snd $ unzip coeffs) ws = w0 : map value vs us = [ w * Const b | (w, b) <- zip ws bs ] head vs <== w0 -- Return the output. return $ sum us Here's the generated C. Note the filter calculation is done entirely by function __r0: static unsigned long long __global_clock = 0; static const unsigned long __coverage_len = 1; static unsigned long __coverage[1] = {0}; static unsigned long __coverage_index = 0; static float __v1 = 0; /* filter.filter.filter2 */ static float __v0 = 0; /* filter.filter.filter1 */ /* filter.filter */ static void __r0(void) { unsigned char __0 = 1; float __1 = 0.0; float __2 = input; float __3 = __1 + __2; float __4 = __v0 /* filter.filter.filter1 */ ; float __5 = -2.0; float __6 = __4 * __5; float __7 = __3 + __6; float __8 = __v1 /* filter.filter.filter2 */ ; float __9 = -4.0; float __10 = __8 * __9; float __11 = __7 + __10; float __12 = 1.0; float __13 = __11 * __12; float __14 = __1 + __13; float __15 = 3.0; float __16 = __4 * __15; float __17 = __14 + __16; float __18 = 5.0; float __19 = __8 * __18; float __20 = __17 + __19; if (__0) { __coverage[0] = __coverage[0] | (1 << 0); } output = __20; __v0 /* filter.filter.filter1 */ = __11; __v1 /* filter.filter.filter2 */ = __4; } void filter(void) { { static unsigned char __scheduling_clock = 0; if (__scheduling_clock == 0) { __r0(); /* filter.filter */ __scheduling_clock = 0; } else { __scheduling_clock = __scheduling_clock - 1; } } __global_clock = __global_clock + 1; }