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Explicación: por qué wc en Haskell resultó ser "más rápido" que el análogo en C


Después de artículos recientes ( No. 10xd34df00d, №2chapuza, №3picul) comparando la velocidad de las implementaciones de la utilidad wc simplificada , solo tenía una pregunta: ¿cómo resultó una implementación simple en Haskell más rápida que una implementación simple en C ?


2020-02-27 : Los resultados y conclusiones paraghc 8.8.3y sobre los textos de Shakespeare se confirman(al final bajo el spoiler).


Brevemente recuerde TK


Para un archivo de texto de 1.8Gb (1_871_822_210 bytes), debe contar el número de líneas, palabras y caracteres. Con una serie de simplificaciones: solo codificación de caracteres de 8 bits, final de línea solo en estilo Unix, los límites de las palabras son espacios y todos los caracteres son menos Char(14), leyendo solo desde un archivo (la asignación de memoria es aceptable).


Datos de prueba de muestra

Region,Country,Item Type,Sales Channel,Order Priority,Order Date,Order ID,Ship Date,Units Sold,Unit Price,Unit Cost,Total Revenue,Total Cost,Total Profit
Sub-Saharan Africa,South Africa,Fruits,Offline,M,7/27/2012,443368995,7/28/2012,1593,9.33,6.92,14862.69,11023.56,3839.13
Middle East and North Africa,Morocco,Clothes,Online,M,9/14/2013,667593514,10/19/2013,4611,109.28,35.84,503890.08,165258.24,338631.84
Australia and Oceania,Papua New Guinea,Meat,Offline,M,5/15/2015,940995585,6/4/2015,360,421.89,364.69,151880.40,131288.40,20592.00
Sub-Saharan Africa,Djibouti,Clothes,Offline,H,5/17/2017,880811536,7/2/2017,562,109.28,35.84,61415.36,20142.08,41273.28
Europe,Slovakia,Beverages,Offline,L,10/26/2016,174590194,12/4/2016,3973,47.45,31.79,188518.85,126301.67,62217.18
Asia,Sri Lanka,Fruits,Online,L,11/7/2011,830192887,12/18/2011,1379,9.33,6.92,12866.07,9542.68,3323.39
Sub-Saharan Africa,Seychelles ,Beverages,Online,M,1/18/2013,425793445,2/16/2013,597,47.45,31.79,28327.65,18978.63,9349.02
Sub-Saharan Africa,Tanzania,Beverages,Online,L,11/30/2016,659878194,1/16/2017,1476,47.45,31.79,70036.20,46922.04,23114.16
Sub-Saharan Africa,Ghana,Office Supplies,Online,L,3/23/2017,601245963,4/15/2017,896,651.21,524.96,583484.16,470364.16,113120.00
Sub-Saharan Africa,Tanzania,Cosmetics,Offline,L,5/23/2016,739008080,5/24/2016,7768,437.20,263.33,3396169.60,2045547.44,1350622.16
Asia,Taiwan,Fruits,Offline,M,2/9/2014,732588374,2/23/2014,8034,9.33,6.92,74957.22,55595.28,19361.94
Middle East and North Africa,Algeria,Cosmetics,Online,M,2/18/2011,761723172,2/24/2011,9669,437.20,263.33,4227286.80,2546137.77,1681149.03
Asia,Singapore,Snacks,Online,C,1/28/2013,176461303,2/7/2013,7676,152.58,97.44,1171204.08,747949.44,423254.64
Australia and Oceania,Papua New Guinea,Clothes,Offline,L,6/20/2011,647164094,7/14/2011,9092,109.28,35.84,993573.76,325857.28,667716.48
Asia,Vietnam,Personal Care,Online,M,4/4/2010,314505374,5/6/2010,7984,81.73,56.67,652532.32,452453.28,200079.04
Sub-Saharan Africa,Uganda,Personal Care,Online,M,6/19/2014,539471471,7/21/2014,451,81.73,56.67,36860.23,25558.17,11302.06
Sub-Saharan Africa,Zimbabwe,Office Supplies,Offline,C,3/28/2011,953361213,4/8/2011,9623,651.21,524.96,6266593.83,5051690.08,1214903.75
Sub-Saharan Africa,Ethiopia,Cosmetics,Online,M,7/7/2011,807785928,7/25/2011,662,437.20,263.33,289426.40,174324.46,115101.94
Europe,France,Cosmetics,Online,M,12/7/2015,324669444,1/18/2016,5758,437.20,263.33,2517397.60,1516254.14,1001143.46


Resultados anteriores


"" , . i7-4600U CPU @ 2.10GHz. — . , /dev/shm/ (tmpfs).


" ", Haskell- ( , CPU):


wc-19.416
Haskellghc 8.0.2, -O22.811
gcc 8, -Ofast3.067
gcc 8, -Ofast0.637

, () - Haskell. - "". ghc (2.811 < 3.067), Haskell 2:3 Haskell. .


, . , AVX2:


Haskellghc 8.0.2, -O2 -mavx22,789
gcc 8, -Ofast -march=haswell2.914
clang 8, -Ofast -march=haswell1.124
gcc 8, -Ofast -march=haswell0.634
AVX2gcc 8, -Ofast -march=haswell0.269

, AVX2 Haskell, clang ( CompilerExplorer), . , AVX2 .


- Haskell


. , .


, -ddump-asm. wc.hs 24 . - , grep cmp : cmpq $33,%rbx; cmpq $32,%rbx; cmpq $10,%rbx; cmpb $4,%bl. .


- . C:


static _Bool process_chunk(const unsigned char *text, const size_t bytes,
                           _Bool prev) {
  result.chars += bytes;
  for (size_t i = 0; i < bytes;) {
    if (text[i] > ' ') {
      // -  ""
      result.words += !prev;
      prev = 1;
      while (++i < bytes && text[i] > ' ')
        ;
    } else {
      // -  
      prev = 0;
      do {
        _Bool non_space = text[i] != ' ' && text[i] - 9 > 4;
        result.words += !prev && non_space;
        result.lines += text[i] == '\n';
        prev = non_space;
      }
      while (++i < bytes && text[i] <= ' ');
    }
  }
  return prev;
}

Haskell-, . , "" :


Haskellgcc 8, -Ofast1.331
Haskellghc 8.0.2, -O22.811
gcc 8, -Ofast3.067
gcc 8, -Ofast0.637

"" Haskell- , ! , , ghc .


Haskell C, ( ):


  • ghc decision tree , . -: " " " ".
  • - " " , -. , , "" 1.8 ;)
  • , . , "" - ( ). — .

, 1871822210 / 44774631 = 41.8 , 44774631 / 15000000 = 2.98 .
-. - , . ?


1.8 (3068561 * 610 = 1871822210):


$ dd if=/dev/urandom of=/dev/shm/rand.dat bs=3068561 count=610

, " " , "" . 1871822210 / 210195110 = 8.9, . , "" . , "" 41 . "" :


Haskellgcc 8, -Ofast1.331 => 3.532
Haskellghc 8.0.2, -O22.811 => 4.812
gcc 8, -Ofast3.062 => 3.071

- — . , C. .


Haskell "" , . , , C - ;)


ghc 8.8.3 (2020-02-27)

:


  1. - LLVM.
  2. gcc clang.
  3. , .
  4. , "" Haskell () .
  5. wc .

. i7-7820HQ CPU @ 2.90GHz 64- Fedora 31.


5_777_367 . " " 1.8:


$ wget http://www.gutenberg.org/files/100/100-0.txt
$ for i in `seq 1 333`; do cat 100-0.txt >> test.txt; done

1_923_863_211 . C :


wc-12.687
Haskellgcc 9.2.1, -Ofast4.947
Haskellclang 9.0.1, -Ofast4.689
Haskellghc 8.8.3, -O36.339 (!)
Haskellghc 8.8.3, -O3 -fllvm4.893 (!)
gcc 9.2.1, -Ofast2.445
clang 9.0.1, -Ofast2.347

/dev/urandom 1_871_822_210 :


wc-16.878
Haskellgcc 9.2.1, -Ofast3.322
Haskellclang 9.0.1, -Ofast3.344
Haskellghc 8.8.3, -O33.976
Haskellghc 8.8.3, -O3 -fllvm2.513
gcc 9.2.1, -Ofast2.376
clang 9.0.1, -Ofast2.244

ghc 8.8.3 8.0.2, LLVM ( 9.0.1) . , C - , . " " /dev/urandom, .


, 0xd34df00d, Haskell . , .


, , .


!

: "" "" C ( ), : "" . , zero cost abstraction , zero cost abstraction .

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