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Editorial Team
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Asked: 2026-06-14T10:03:17+00:00

After profiling my haskell program, I’ve found that 66% of the time in the

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After profiling my haskell program, I’ve found that 66% of the time in the program is spent indexing into lists. The solution seems to be using Data.Vector, but I’m having trouble converting: when I change the code to use a Vector it uses tons and tons of memory, and hangs so badly I can’t even profile it. What could cause this?

Here is the file I would like to convert: https://github.com/drew-gross/Blokus-AI/blob/master/Grid.hs

and my attempt at converting it: https://github.com/drew-gross/Blokus-AI/blob/convert-to-vector/Grid.hs

Any ideas what I am doing wrong? Or at least, where to look?

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1 Answer

  1. Editorial Team
    makeEmptyGrid width height defaultCell = Grid (Data.Vector.take arraySize $ fromList $ repeat defaultCell) width height

    That’s a killer right there. fromList converts an entire list to a Vector, but repeat defaultCell is an infinite list.

    makeEmptyGrid width height defaultCell = Grid (fromListN arraySize $ repeat defaultCell) width height

    or

    makeEmptyGrid width height defaultCell = Grid (fromList $ replicate arraySize defaultCell) width height

    would fix that.

    A cursory look over the rest didn’t result in further obvious traps, but I may easily have overlooked some.

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