Re: memory pool algorithms

You still pay the cost for a variable shift when setting a bit on some platforms.

MSN
-----Original Message-----
From: Alan Latham [mailto:[email protected]]
Sent: Friday, April 24, 2009 9:53 AM
To: Game Development Algorithms
Subject: Re: [Algorithms] memory pool algorithms

unless you add hierarchy to the bit-vector..

----- Original Message -----
From: "Tom Plunket" <[email protected]>
To: "Game Development Algorithms" <[email protected]>
Sent: Saturday, April 25, 2009 2:09 AM
Subject: Re: [Algorithms] memory pool algorithms


>>> then clearly moving things around shouldn't be too terrible.  I believe
>>> keeping a parallel bitfield would be more straight forward than an
>>> unsorted array of free elements.
>>
>> So with the parallel bit-field, each bit indicates whether the element
>> has
>> been allocated, and when you iterate over all elements you skip elements
>> without a set bit?
>
> That was my thinking, with the 30 seconds I spent on the problem.  ;)
>
> I'm not sure if it's ideal, and I'm sure its power would show off
> differently in sparse vs. not allocation patterns, but compared to an
> array of integers that would require traversing the allocations in
> arbitrary order I think it would considerably outperform this.  However,
> I'm also aware that setting bits in bitfields is horrifically slow on some
> platforms, so you'd probably want to write whatever your solution was in
> assembler so that you could optimally schedule memory reads and writes.
> (I did battle with a certain compiler this week on just this front, but my
> solution was to remove the need for the set bits at all.)
>
> -tom!
>
> --
>
>
>
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