Parallelization on muli-CPU hardware?

Steve Holden steve at holdenweb.com
Thu Oct 7 00:40:26 CEST 2004


Neil Hodgson wrote:

> Steve Holden:
> 
> 
>>Until that time I hadn't realized that the laptop was built on a
>>multi-core processor.
> 
> 
>    It is more likely you had a machine that featured 'hyperthreading' which
> is much less than multiple cores. Somewhere between two sets of registers
> and two processors.
> 
Aah, the penny drops and I realize you are indeed correct. It's  using 
hyperthreading.
> 
>>Fortunately the task was easily partitioned into
>>two independent processes, each dealing with a separate set of database
>>rows, so the run completed well under the necessary 24 hours.
> 
> 
>    Did you measure a real performance increase, that is, elapsed time to
> completion of job? Many benchmarks show minimal or even negative performance
> improvements for hyperthreading. Relying on secondary indicators such as CPU
> busyness can be misleading.
> 

No, I *was* actually measuring elapsed time to completion, and I was 
surprised that the speedup was indeed just about linear. Not often you 
come across a task that can be cleanly partitioned in that way.

regards
  Steve
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