[GHC] #9120: Cache intermediate powers

[GHC]

#9120: Cache intermediate powers
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              Reporter:  basvandijk  |            Owner:  ekmett
                  Type:  feature     |           Status:  new
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.8.2
             Component:  Core        |         Keywords:
  Libraries                          |     Architecture:  Unknown/Multiple
            Resolution:              |       Difficulty:  Unknown
      Operating System:              |       Blocked By:
  Unknown/Multiple                   |  Related Tickets:
       Type of failure:  Runtime     |
  performance bug                    |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by ekmett):

 This seems pretty straight forward and the code looks correct to me.

 The main cost being borne right now is that rather than being `O(n)` to
 compute the array it is `O(n log n)`.

 With `n` bounded above by `1100`, and it only hitting you while you force
 these constants the first time it'll be hard to find a benchmark
 materially affected, as they 'warm up' more or less instantly.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9120#comment:7>
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