[Haskell-cafe] performance issues with popCount
johan.tibell at gmail.com
Sat Sep 8 00:55:43 CEST 2012
On Fri, Sep 7, 2012 at 4:54 AM, Nicolas Trangez <nicolas at incubaid.com> wrote:
> On Thu, 2012-09-06 at 12:07 -0700, Johan Tibell wrote:
>> Have a look at the popCount implementation for e.g. Int, which are
>> written in C and called through the FFI:
> Out of interest: isn't this compiled into the popCnt# primop (and popcnt
> instruction on SSE4.2)?
It's the other way around the popCnt# primop is compiled into either
calls to these C functions or into the popcnt instruction, if -msse4.2
> I recently noticed Data.IntSet also contains a fairly basic "bitcount"
> implementation . Is this kept as-is for a reason, instead of using
> popCount from Data.Bits?
I don't think so, except that we want to support the last 3 released
versions of GHC so we need to have a fallback if Data.Bits.popCount
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