Re: [boost] [Endian] Performance

Subject: Re: [boost] [Endian] Performance
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2011-09-08 09:33:36

On 07/09/2011 21:03, Phil Endecott wrote:

> Increasing the block size doesn't make any significant difference;
> reducing it below 4096 bytes does slow it down.
>
> So the overhead of byteswapping compared to I/O - for a file cached in
> memory - is between about 25% (case 3) and 150% (case 4) on this system.

So std::reverse is six times slower than std::transform in that benchmark.
Not entirely unexpected, especially on ARM.

> So as expected the amount of CPU time used scales approximately as
> before, but the elapsed time doesn't change as it's limited by the SATA
> interface or SSD to around 50 MB/sec.
>
> Personally I think these savings are worthwhile, and I believe that a
> library developer should normally assume that potential users of a
> library will have applications that need optimal performance, even if
> the developer is happy with something more modest.

The conclusion seems to be "doesn't matter for bandwidth, but does for 
latency".

I take it that high-speed trading stuff needs the lowest latency possible?