Re: About the Amdahl law

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From	Ramine <ramine@1.1>
Newsgroups	comp.programming
Subject	Re: About the Amdahl law
Date	Sat, 15 Nov 2014 15:38:04 -0800
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On 11/15/2014 3:36 PM, Ramine wrote:
>
> Hello,
>
>
> I think that the Amdahl law is very important, cause it permits
> us to understand better multicore programming and distributed
> programming, for example when you are doing a parallel matrix
> multiplication, you have to move two doubles and you have also to
> multiply them, an the act to multiplying them inside your computers will
> tale around 8 clocks if we don't use SIMD instructions, and the act to


around 8 clocks on x86 computers i mean.

> move the two doubles from the memory to the CPU will take around 1
> clock, so the parallel matrix multiplication will not scale more than 8X
> and that's what the Amdahl lawsays, and that's because of contention on
> the memory bus that must serialize the accesses to the memomoy , for the
> concurrent hashtable that's the same , if the data on the corresponding
> keys of the hashtable are more bigger so the data moving from the memory
> to the CPU will take much more CPU clocks and this will make the serial
> part of the Amdahl equation bigger , so this will make the concurrent
> hashtable to scale less and less, and that's also the Amdahl equation
> that says that... for databases systems such us Oracle they don't scale
> well on multicore systems, cause they are memory bound, so this is why
> you have to scale them by distributing your database on many computers
> and this will make the memory system and hardisk system truly parallel
> for the read transations and this is much better and that's also the
> Amdahl equation who says that, so all in all the Amdahl equation is a
> good tool that that modifies our perception on parallel programming and
> that permit us to undertand better the inner side of parallel programming.
>
>
>
> Thank you,
> Amine Moulay Ramdane.
>
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About the Amdahl law Ramine <ramine@1.1> - 2014-11-15 15:36 -0800
  Re: About the Amdahl law Ramine <ramine@1.1> - 2014-11-15 15:38 -0800

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