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Searching arrays in X86 assembler with a bloom filter pt 3

Started by phildawes · 9 months ago

Continuing on from yesterday evening, I had a bit of time tonight in front of the telly so I implemented the rest of the fast-search functionality in factor using the assembler code from the previous post.
The first step was to create the simple bloom filter for sending to the assember code. To ... Continue reading »

4 comments

  • Anonymous

    10 months ago

    You can shift by the contents of the CL register, e.g. shl %cl, %eax .
    reply
  • Asm

    10 months ago

    Variable shifts have the count in %cl.

    But why bother? bt r,r and bt r,i are only 1 uop on a Core2. Check the instruction timings here: http://www.agner.org/optimize/

    Use mov (%eax,%edi,4), %edi and drop the shl $0x2, %edi.
    reply
  • Phil Dawes

    10 months ago

    @Asm - thanks for the link, that's a handy resource
    reply
  • Phil Dawes

    10 months ago

    Slava Pestov wrote:
    > Hi Phil,
    >
    > I couldn't post a comment on your blog for some reason so I'm posting
    > this to the list instead.
    >
    > The seq>hash word you write already exists in the sets vocabulary, its
    > called unique.
    >
    > And (prepare-filter) looks nicer if you use fry:
    >
    > : (prepare-filter) ( filter seq -- )
    > '[ 1048576 mod _ set-bit ] each ;
    >
    > Slava
    reply

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