[MLton-user] timing anomoly

[Matthew Fluet]

Good point.  Due to prompting from a user ;-), MLton carefully doesn't do 
constant folding or common subexpression elimination on floating point 
operations, since that wouldn't respect the rounding mode.  (Actually, in 
this situation we could do better, since it would be acceptable to do CSE 
on the straight-line code where there are no intervening calls to change 
the program rounding mode state.)

On Tue, 4 Dec 2007, Sean McLaughlin wrote:
> Oh, I'm sorry!  Thanks for this.  It was keeping me up at night.
>
> On Dec 4, 2007 2:12 PM, Vesa Karvonen <vesa.a.j.k at gmail.com> wrote:
>> On Dec 4, 2007 6:48 PM, Sean McLaughlin <seanmcl at gmail.com> wrote:
>>> Fair enough :)
>>>
>>> However, is it possible to make this code run faster?  It currently runs
>>> over 3X slower than the equivalent C program:
>> [...]
>>
>> I compiled the code snippets with both MLton and gcc (-O2) and
>> inspected the generated assembly code.  What is happening here is that
>> gcc eliminates most of the floating point computation.  Note that all
>> of your "x" variables are constants.  You should read the "x" values
>> from some run-time input for a more meaningful benchmark.
>>
>> -Vesa Karvonen
>>
>
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