RTS option

ghcで生成した実行ファイルを実行する時に指定する

実行時の統計を出力する

使っている例

code:hs

module Bar where

main :: IO ()

main = print $ fib 40

fib n = if n < 2 then 1 else fib (n - 1) + fib (n - 2)

$ stack ghc -- -main-is Bar src/Bar.hs -O2

$ ./Bar +RTS -s

code:result

λ ./src/Bar +RTS -s

165580141

7,947,930,784 bytes allocated in the heap

2,144,192 bytes copied during GC

44,376 bytes maximum residency (2 sample(s))

29,352 bytes maximum slop

2 MiB total memory in use (0 MB lost due to fragmentation)

Tot time (elapsed) Avg pause Max pause

Gen 0 7578 colls, 0 par 0.017s 0.034s 0.0000s 0.0000s

Gen 1 2 colls, 0 par 0.000s 0.000s 0.0001s 0.0001s

INIT time 0.000s ( 0.003s elapsed)

MUT time 4.288s ( 4.314s elapsed)

GC time 0.017s ( 0.034s elapsed)

EXIT time 0.000s ( 0.007s elapsed)

Total time 4.306s ( 4.358s elapsed)

%GC time 0.0% (0.0% elapsed)

Alloc rate 1,853,399,829 bytes per MUT second

Productivity 99.6% of total user, 99.0% of total elapsed