Pass Zeiger auf ein Array in Haskell zu einer C-Funktion

Question

Ich habe den folgende C-Code:

#include <sys/times.h> 
#include <time.h> 


float etime_(float *tarray) 
{ struct tms buf; 

    times(&buf); 

    tarray[0] = 1.0 * buf.tms_utime/CLOCKS_PER_SEC; 
    tarray[1] = 1.0 * buf.tms_stime/CLOCKS_PER_SEC; 

    return tarray[0] + tarray[1]; 
} 

diesen Fortran-Code zu Haskell zu Port Versuch:

PROGRAM Test 
    IMPLICIT NONE 

    REAL t, ta(2), etime 

    INTEGER i 
    DOUBLE PRECISION x 

    do i = 1, 10000 
     x = sin(cos(i * 1.0 d0)) 
     print *, x 
    enddo 

    ta(1) = 0.0d0 
    ta(2) = 0.0d0 

    t = etime(ta)  

    PRINT *, 'user time: ', ta(1) 
    PRINT *, 'system time: ', ta(2) 
    PRINT *, 'process time: ', t 

    END 

Wie kann ich Array definieren und ! oder !!! für den folgenden Code zu arbeiten?

module Main where 

import GHC.Ptr 
import GHC.Prim 
import System.IO.Unsafe 
import Control.Monad 

foreign import ccall etime_ :: Ptr Double → IO Double 
etime = etime_ 

main :: IO Int 
main = do 
    mapM_ (print . sin . cos . (* (1.0 :: Double)) . fromIntegral) [1..10000 :: Int] 
    ta ← array 2 
    t ← etime ta 
    putStrLn $ "user time: " ++ show (ta !!! 0) 
    putStrLn $ "system time: " ++ show (ta !!! 1) 
    putStrLn $ "process time: " ++ show t 
    return 0 

array :: Int → IO (Ptr a) 
array size = undefined 

(!) :: Ptr a → Int → IO a 
(!) = undefined 

(!!!) :: Ptr a → Int → a 
(!!!) = undefined 

Answer 1

Ich schlage vor, diese:

{-# LANGUAGE ForeignFunctionInterface #-} 

import Foreign.Marshal.Array (allocaArray, peekArray) 
import Foreign.Ptr (Ptr) 

foreign import ccall etime_ :: Ptr Float -> IO Float 

main :: IO() 
main = do 
    mapM_ (print . sin . cos . (* (1.0 :: Double)) . fromIntegral) [1..10000 :: Int] 
    allocaArray 2 $ \ta -> do 
    ptime <- etime_ ta 
    [utime, stime] <- peekArray 2 ta 
    putStrLn $ "user time: " ++ show utime 
    putStrLn $ "system time: " ++ show stime 
    putStrLn $ "process time: " ++ show ptime 

aber, spezifische Fragen zu beantworten:

array :: Storable a => Int -> IO (Ptr a) 
array = mallocArray 

(!) :: Storable a => Ptr a -> Int -> IO a 
(!) = peekElemOff 

(!!!) :: Storable a => Ptr a -> Int -> a 
(!!!) ptr = unsafePerformIO . peekElemOff ptr 

Ich schlage vor, die Funktionen zu finden, zu verwenden Hoogle Sie benötigen.

Answer 2

Geben Sie die Summe, die Benutzerzeit und die Systemzeit als Tupel ein. Beachten Sie nimmt, dass etime einen Zeiger zu schweben, nicht zu verdoppeln, so machen Sie Ihre Arten einig:

{-# LANGUAGE ForeignFunctionInterface #-} 

module Main where 

import Foreign (Ptr) 
import Foreign.Marshal.Array (allocaArray,peekArray) 
import Control.Monad (mapM_) 

foreign import ccall etime_ :: Ptr Float -> IO Float 

etime :: IO (Float, Float, Float) 
etime = do 
    allocaArray 2 $ \ta -> do 
    t <- etime_ ta 
    [user,sys] <- peekArray 2 ta 
    return (t,user,sys) 

main :: IO Int 
main = do 
    mapM_ (print . sin . cos . (* (1.0 :: Double)) . fromIntegral) [1..10000 :: Int] 
    (t,user,sys) <- etime 
    putStrLn $ "user time: " ++ show user 
    putStrLn $ "system time: " ++ show sys 
    putStrLn $ "process time: " ++ show t 
    return 0 

Answer 3

die folgenden zusätzlichen Haskell Modul Gegeben:

module AllocSymbols (

    (↑≣), -- mallocArray 
    (≣⊠), -- free 

    (≣→), -- peekElemOff 
    (≣←), -- pokeElemOff 

    (⥱), -- peekElemOff unsafe 

    (⥅), -- advancePtr 

) where 

import GHC.Ptr 
import System.IO.Unsafe 
import Foreign.Storable 
import Foreign.Marshal.Alloc (free) 
import Foreign.Marshal.Array 

(↑≣) :: Storable a ⇒ Int → IO (Ptr a) 
(↑≣) = mallocArray 

(⥱) :: Storable a ⇒ Ptr a → Int → a 
a ⥱ i = unsafePerformIO $ peekElemOff a i 

(≣→) :: Storable a ⇒ Ptr a → Int → IO a 
(≣→) = peekElemOff 

(≣←) :: Storable a ⇒ Ptr a → Int → a → IO() 
(≣←) = pokeElemOff 

(⥅) :: Storable a ⇒ Ptr a → Int → Ptr a 
(⥅) = advancePtr 

(≣⊠) :: Ptr a → IO() 
(≣⊠) = Foreign.Marshal.Alloc.free 

---

Und wir können Port dieses Stück Fortran-Code:

PROGRAM Test 
    IMPLICIT NONE 

    REAL t, ta(2), etime 

    INTEGER i 
    DOUBLE PRECISION x 

    do i = 1, 10000 
     x = sin(cos(i * 1.0 d0)) 
     print *, x 
    enddo 

    ta(1) = 0.0d0 
    ta(2) = 0.0d0 

    t = etime(ta)  

    PRINT *, 'user time: ', ta(1) 
    PRINT *, 'system time: ', ta(2) 
    PRINT *, 'process time: ', t 

    END 

Wort für Wort zu Haskell:

module Main where 

import GHC.Ptr 
import AllocSymbols 
import Control.Monad 

foreign import ccall etime_ :: Ptr Float → IO Float 

main :: IO() 
main = do 
    mapM_ (print . sin . cos . (* (1.0 :: Double)) . fromIntegral) [1 .. 10000 :: Int] 

    ta ← (2 ↑≣) -- ta :: Ptr Float 

    (ta ≣← 0) 0.0 
    (ta ≣← 1) 0.0 

    t ← etime_ ta 

    putStrLn $ " user time: " ++ show (ta ⥱ 0) 
    putStrLn $ " system time: " ++ show (ta ⥱ 1) 
    putStrLn $ " process time: " ++ show t 

    (ta ≣⊠) -- optional in this case