Floating point performance

[Julian Seward (Intl Vendor)]

I tried this, with ghc-4.08.1 -O both with and without
profiling, on a Sparc box of I believe around 300 MHz,
and I can't reproduce it at all.  Without profiling, 
it allocates about 505 k of heap and runs in 0.02
seconds.

Ummm ?

J

| -----Original Message-----
| From: Jan Kort [mailto:kort@wins.uva.nl]
| Sent: Friday, January 26, 2001 4:40 PM
| To: glasgow-haskell-users@haskell.org
| Subject: Floating point performance
| 
| 
| Hi,
| I noticed ghc (version 4.08.1) floating point performance is
| really slow on my computer: a 270Mhz sun ultra5. The program
| below does 1 milion floating point multiplications and takes
| 2 seconds to run. I made a profile and it says most of the
| time (93%) is spent in the function bar. Any idea what is
| going on ?
| 
| Regards,
|   Jan
| 
| module Main where
| 
| foo :: Double -> [Double]
| foo 0 = [1]
| foo n = bar n:foo (n-1)
| 
| bar :: Double -> Double
| bar n = n*1*1*1*1*1*1*1*1*1*1
|          *1*1*1*1*1*1*1*1*1*1
|          *1*1*1*1*1*1*1*1*1*1
|          *1*1*1*1*1*1*1*1*1*1
|          *1*1*1*1*1*1*1*1*1*1
|          *1*1*1*1*1*1*1*1*1*1
|          *1*1*1*1*1*1*1*1*1*1
|          *1*1*1*1*1*1*1*1*1*1
|          *1*1*1*1*1*1*1*1*1*1
|          *1*1*1*1*1*1*1*1*1*1
| 
| foldl'           :: (a -> b -> a) -> a -> [b] -> a
| foldl' _ a []     = a
| foldl' f a (x:xs) = (foldl' f $! f a x) xs
| 
| main :: IO()
| main = putStrLn (show (foldl' (+) 0 (foo 10000)))
| 
| ---------------------------
| Profile:
| 
|         total time  =        2.60 secs   (130 ticks @ 20 ms)
|         total alloc =  24,845,828 bytes  (excludes profiling 
| overheads)
| 
| COST CENTRE          MODULE     %time %alloc
| 
| bar                  Main        93.1   96.1
| foo                  Main         3.1    2.4
| foldl'               Main         3.1    1.4
| 
| 
|                                               individual     inherited
| COST CENTRE              MODULE     entries  %time %alloc   
| %time %alloc
| 
| MAIN                     MAIN             0    0.0   0.0    
| 100.0 100.0
|  main                    Main             0    0.0   0.0      
| 0.0   0.0
|  CAF                     PrelShow         1    0.0   0.0      
| 0.0   0.0
|  CAF                     PrelFloat        3    0.0   0.0      
| 0.0   0.0
|  CAF                     PrelHandle       3    0.0   0.0      
| 0.0   0.0
|  CAF                     Main             9    0.0   0.0    
| 100.0 100.0
|   main                   Main             1    0.8   0.0    
| 100.0 100.0
|    foo                   Main         10001    3.1   2.4     
| 96.2  98.5
|     bar                  Main         10000   93.1  96.1     
| 93.1  96.1
|    foldl'                Main         10002    3.1   1.4      
| 3.1   1.4
| 
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