Implementing isFinite by looking at the exponent field would avoid the 
creation of a transient floating point number.

On 12/21/14 13:11 , Eliot Miranda wrote:
> Hi Levente,
>
>      please rewrite using a temp to hold the raw bits, a class var to hold the float array and hexadecimal.  Then one can understand much easier.  Also is inlining isFinite that important for performance?
>
> rawBits := FloatArrayBuffer at: 1 put: self; basicAt: 1
> etc...
>
>
> Eliot (phone hence not writing the full method)
>
> On Dec 20, 2014, at 7:27 PM, Levente Uzonyi <leves at elte.hu> wrote:
>
>> On Sat, 20 Dec 2014, Chris Muller wrote:
>>
>>> On Fri, Dec 19, 2014 at 4:01 PM, Louis LaBrunda
>>> <Lou at keystone-software.com> wrote:
>>>> Hi Chris,
>>>>
>>>> Is this any faster?
>>>>
>>>> Float>>#hashKey32
>>>>
>>>> ^self isFinite ifTrue: [
>>>>         self negative ifTrue: [4286578688 - self asIEEE32BitWord] ifFalse: [self
>>>> asIEEE32BitWord + 2147483651]
>>>> ] ifFalse: [self negative ifTrue: [0] ifFalse: [4294967294]].
>>>
>>> About the same, but I think I like your code better.  Thanks.
>>
>> Dave has already suggested to use a FloatArray for conversion instead of #asIEEE32BitWord. We use this technique in various network protocol implementations, and it works great.
>>
>> Here's a significantly faster, optimized version:
>>
>> hashKey32: aFloatArray
>>
>>     self - self = 0.0 ifTrue: [
>>         self < 0.0 ifTrue: [ ^4286578688 - (aFloatArray at: 1 put: self; basicAt: 1) ].
>>         ^2147483651 + (aFloatArray at: 1 put: self; basicAt: 1) ].
>>     self < 0.0 ifTrue: [ ^0 ].
>>     ^4294967294
>>
>> The argument is any FloatArray instance with at least one slot.
>>
>>
>> Levente
>>
>>
>
>