Seqs in nim have value type semantics. Your inner loop ( for d in Directions)
actually assigns Directions[...] to d on every iteration which involves full
copy of the seq. Here's the patched version. I have also preallocated result
seq.
import times, os
var board: seq[char] = @['0', 'p', '.', 'p', 'P', '.', 'p', 'P', '.', 'p',
'.', 'p', 'P', '.', 'p']
const NE: seq[int] = @[8, 2, 13, 4, 5, 7, 8, 3, 9, 12, 7, 8, 3, 9, 12]
const Directions = [NE, NE, NE, NE] # for short: in real application the
array elements differ
proc do_something(board: openarray[char]): seq[char] =
result = newSeq[char](board.len * Directions.len)
var ir = 0
for i, p in board:
for d in 0 ..< Directions.len:
result[ir] = board[Directions[d][i]]
inc ir
let t0 = cpuTime()
var res: seq[char]
let count = 100000
for i in 1..count:
res = do_something(board)
let t1 = cpuTime()
echo "***** Time elapsed for Nim: ", $(t1 - t0), " Counts: ", $count
