I investigated accelerate
and accelerate-cuda
and put some debug code to measure a time both under ghci and in a compiled, optimised version.
Results are below, you can see stack trace and execution times.
ghci run
$ ghc -O2 -dynamic -c -threaded Main.hs && ghci
GHCi, version 7.8.3: http://www.haskell.org/ghc/ :? for help
…
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Ok, modules loaded: Main.
Prelude Main> Loading package transformers-0.3.0.0 ... linking ... done.
…
Loading package array-0.5.0.0 ... linking ... done.
(...)
Loading package accelerate-cuda-0.15.0.0 ... linking ... done.
>>>>> run
>>>>> runAsyncIn.execute
>>>>> runAsyncIn.seq ctx
<<<<< runAsyncIn.seq ctx: 4.1609e-2 CPU 0.041493s TOTAL
>>>>> runAsyncIn.seq a
<<<<< runAsyncIn.seq a: 1.0e-6 CPU 0.000001s TOTAL
>>>>> runAsyncIn.seq acc
>>>>> convertAccWith True
<<<<< convertAccWith: 0.0 CPU 0.000017s TOTAL
<<<<< runAsyncIn.seq acc: 2.68e-4 CPU 0.000219s TOTAL
>>>>> evalCUDA
>>>>> push
<<<<< push: 0.0 CPU 0.000002s TOTAL
>>>>> evalStateT
>>>>> runAsyncIn.compileAcc
>>>>> compileOpenAcc
>>>>> compileOpenAcc.traveuseAcc.Alet
>>>>> compileOpenAcc.traveuseAcc.Use
>>>>> compileOpenAcc.traveuseAcc.use3
>>>>> compileOpenAcc.traveuseAcc.use1
<<<<< compileOpenAcc.traveuseAcc.use1: 0.0 CPU 0.000001s TOTAL
>>>>> compileOpenAcc.traveuseAcc.use2
>>>>> compileOpenAcc.traveuseAcc.seq arr
<<<<< compileOpenAcc.traveuseAcc.seq arr: 0.105716 CPU 0.105501s TOTAL
>>>>> useArrayAsync
<<<<< useArrayAsync: 1.234e-3 CPU 0.001505s TOTAL
<<<<< compileOpenAcc.traveuseAcc.use2: 0.108012 CPU 0.108015s TOTAL
<<<<< compileOpenAcc.traveuseAcc.use3: 0.108539 CPU 0.108663s TOTAL
<<<<< compileOpenAcc.traveuseAcc.Use: 0.109375 CPU 0.109005s TOTAL
>>>>> compileOpenAcc.traveuseAcc.Fold1
>>>>> compileOpenAcc.traveuseAcc.Avar
<<<<< compileOpenAcc.traveuseAcc.Avar: 0.0 CPU 0.000001s TOTAL
>>>>> compileOpenAcc.traveuseAcc.Avar
<<<<< compileOpenAcc.traveuseAcc.Avar: 0.0 CPU 0s TOTAL
>>>>> compileOpenAcc.traveuseAcc.Avar
<<<<< compileOpenAcc.traveuseAcc.Avar: 0.0 CPU 0.000001s TOTAL
>>>>> compileOpenAcc.traveuseAcc.Avar
<<<<< compileOpenAcc.traveuseAcc.Avar: 0.0 CPU 0s TOTAL
<<<<< compileOpenAcc.traveuseAcc.Fold1: 2.059e-3 CPU 0.002384s TOTAL
<<<<< compileOpenAcc.traveuseAcc.Alet: 0.111434 CPU 0.112034s TOTAL
<<<<< compileOpenAcc: 0.11197 CPU 0.112615s TOTAL
<<<<< runAsyncIn.compileAcc: 0.11197 CPU 0.112833s TOTAL
>>>>> runAsyncIn.dumpStats
<<<<< runAsyncIn.dumpStats: 2.0e-6 CPU 0.000001s TOTAL
>>>>> runAsyncIn.executeAcc
>>>>> executeAcc
<<<<< executeAcc: 8.96e-4 CPU 0.00049s TOTAL
<<<<< runAsyncIn.executeAcc: 9.36e-4 CPU 0.0007s TOTAL
>>>>> runAsyncIn.collect
<<<<< runAsyncIn.collect: 0.0 CPU 0.000027s TOTAL
<<<<< evalStateT: 0.114156 CPU 0.115327s TOTAL
>>>>> pop
<<<<< pop: 0.0 CPU 0.000002s TOTAL
>>>>> performGC
<<<<< performGC: 5.7246e-2 CPU 0.057814s TOTAL
<<<<< evalCUDA: 0.17295 CPU 0.173943s TOTAL
<<<<< runAsyncIn.execute: 0.215475 CPU 0.216563s TOTAL
<<<<< run: 0.215523 CPU 0.216771s TOTAL
Array (Z) [1000001.0]
0.217148s
Prelude Main> Leaving GHCi.
compiled code run
$ ghc -O2 -threaded Main.hs && ./Main
[1 of 1] Compiling Main ( Main.hs, Main.o )
Linking Main ...
>>>>> run
>>>>> runAsyncIn.execute
>>>>> runAsyncIn.seq ctx
<<<<< runAsyncIn.seq ctx: 4.0639e-2 CPU 0.041498s TOTAL
>>>>> runAsyncIn.seq a
<<<<< runAsyncIn.seq a: 1.0e-6 CPU 0.000001s TOTAL
>>>>> runAsyncIn.seq acc
>>>>> convertAccWith True
<<<<< convertAccWith: 1.2e-5 CPU 0.000005s TOTAL
<<<<< runAsyncIn.seq acc: 1.15e-4 CPU 0.000061s TOTAL
>>>>> evalCUDA
>>>>> push
<<<<< push: 2.0e-6 CPU 0.000002s TOTAL
>>>>> evalStateT
>>>>> runAsyncIn.compileAcc
>>>>> compileOpenAcc
>>>>> compileOpenAcc.traveuseAcc.Alet
>>>>> compileOpenAcc.traveuseAcc.Use
>>>>> compileOpenAcc.traveuseAcc.use3
>>>>> compileOpenAcc.traveuseAcc.use1
<<<<< compileOpenAcc.traveuseAcc.use1: 0.0 CPU 0.000001s TOTAL
>>>>> compileOpenAcc.traveuseAcc.use2
>>>>> compileOpenAcc.traveuseAcc.seq arr
<<<<< compileOpenAcc.traveuseAcc.seq arr: 3.6651e-2 CPU 0.03712s TOTAL
>>>>> useArrayAsync
<<<<< useArrayAsync: 1.427e-3 CPU 0.001427s TOTAL
<<<<< compileOpenAcc.traveuseAcc.use2: 3.8776e-2 CPU 0.039152s TOTAL
<<<<< compileOpenAcc.traveuseAcc.use3: 3.8794e-2 CPU 0.039207s TOTAL
<<<<< compileOpenAcc.traveuseAcc.Use: 3.8808e-2 CPU 0.03923s TOTAL
>>>>> compileOpenAcc.traveuseAcc.Fold1
>>>>> compileOpenAcc.traveuseAcc.Avar
<<<<< compileOpenAcc.traveuseAcc.Avar: 2.0e-6 CPU 0.000001s TOTAL
>>>>> compileOpenAcc.traveuseAcc.Avar
<<<<< compileOpenAcc.traveuseAcc.Avar: 2.0e-6 CPU 0.000001s TOTAL
>>>>> compileOpenAcc.traveuseAcc.Avar
<<<<< compileOpenAcc.traveuseAcc.Avar: 0.0 CPU 0.000001s TOTAL
>>>>> compileOpenAcc.traveuseAcc.Avar
<<<<< compileOpenAcc.traveuseAcc.Avar: 0.0 CPU 0.000001s TOTAL
<<<<< compileOpenAcc.traveuseAcc.Fold1: 1.342e-3 CPU 0.001284s TOTAL
<<<<< compileOpenAcc.traveuseAcc.Alet: 4.0197e-2 CPU 0.040578s TOTAL
<<<<< compileOpenAcc: 4.0248e-2 CPU 0.040895s TOTAL
<<<<< runAsyncIn.compileAcc: 4.0834e-2 CPU 0.04103s TOTAL
>>>>> runAsyncIn.dumpStats
<<<<< runAsyncIn.dumpStats: 0.0 CPU 0s TOTAL
>>>>> runAsyncIn.executeAcc
>>>>> executeAcc
<<<<< executeAcc: 2.87e-4 CPU 0.000403s TOTAL
<<<<< runAsyncIn.executeAcc: 2.87e-4 CPU 0.000488s TOTAL
>>>>> runAsyncIn.collect
<<<<< runAsyncIn.collect: 9.2e-5 CPU 0.000049s TOTAL
<<<<< evalStateT: 4.1213e-2 CPU 0.041739s TOTAL
>>>>> pop
<<<<< pop: 0.0 CPU 0.000002s TOTAL
>>>>> performGC
<<<<< performGC: 9.41e-4 CPU 0.000861s TOTAL
<<<<< evalCUDA: 4.3308e-2 CPU 0.042893s TOTAL
<<<<< runAsyncIn.execute: 8.5154e-2 CPU 0.084815s TOTAL
<<<<< run: 8.5372e-2 CPU 0.085035s TOTAL
Array (Z) [1000001.0]
0.085169s
As we can see there are two major problems: evaluation of fromList (Z:.1000000) [1..1000000] :: Vector Double
which takes 69 ms extra under ghci (106ms – 37ms), and performGC
call which takes 57 ms extra (58 ms – 1 ms). These two sum up to the difference between execution under ghci and in a compiled version.
I suppose, that in compiled program, RTS manage memory in a different way than in ghci, so allocation and gc can be faster. We can also test only this part evaluating below code (it does not require CUDA at all):
import Data.Array.Accelerate.Array.Sugar
import Data.Time.Clock (diffUTCTime, getCurrentTime)
import System.Mem (performGC)
main :: IO ()
main = do
measure $ seq (fromList (Z:.1000000) [1..1000000] :: Vector Double) $ return ()
measure $ performGC
measure action = do
start <- getCurrentTime
action
end <- getCurrentTime
print $ diffUTCTime end start
Results:
- evaluating vector takes 0.121653s under ghci and 0.035162s in
a compiled version - performGC takes 0.044876s under ghci and
0.00031s in a compiled version.
This could be another question, but maybe someone know: Can we tune somehow garbage collector to work faster under ghci?