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Re: abundant memory?
From: |
Jim Meyering |
Subject: |
Re: abundant memory? |
Date: |
Thu, 24 Jul 2008 11:21:55 +0200 |
Bruno Haible <address@hidden> wrote:
> Jim Meyering wrote:
>> This sounds like an obvious win for linkedhash-list, in these days of
>> inexpensive RAM and the 8GB hobby system. Back when I wrote hash.c,
>> data structure size was the primary constraint in the computational
>> geometry applications I cared about.
>
> Small data structure sizes are still important, because of memory caches:
> There is usually a level-1 cache near the CPU, then a level-2 cache, and then
> only comes the main memory measured in gigabytes. The level-1 cache is often
And then there's L3 cache, and maybe even flash-based cache
before you get to "disk".
No argument from me.
> only a few kilobytes large. You can consider that a memory access to an
> uncached memory location is about 6-8 times slower than a memory access to
> cached memory. (*)
>
> So, the smaller the data structures, the faster your program will be.
> Bit fields are *not* outdated!
Of course not ;-)
My point was that with our much larger RAM sizes today,
the "right" balance for hash.c may now involve using more
memory to save processing time.
Of course, I don't really expect anyone to make changes to
hash.c and to find time to perform all the profiling that'd
be required for justification.