Re: glibc on ARM Processor

[Andreas Jaeger]

"Robert Couse" <address@hidden> writes:

> Mr. Jaeger,
> We are currently working on some C++ software that runs under VxWorks and we
> will be eventually porting it to Linux. The project is an embedded ARM 7
> network IC and we are doing our development work on the ARM Integrator Board
> with a ARM7TDMI. Both VxWorks/Tornado ( WindRiver ) and, of course, Linux
> uses the GNU compiler and the glibc library. We ran into some timing issues
> and, after an investigation, we found out that the issues are in the
> floating point library. We created a benchmark and compared it to our
> previous platform - i960 processor and with the library that is shipped by
> ARM in their Developer Suite. We have also compared it to Newlib with
> comparable results.
> 
> Here is a comparison of running the attached sample code:
> 
> Platform              Tool Vendor     Loop count  Time (seconds)
> -----------------------------------------------------
> i960jx 33mhz          Tornado (gnu)   100,000     8

> ARM7TDMI 20 Mhz       Tornado (gnu)     1,000     13
> ARM7TDMI 20 Mhz       ARM             100,000     23

Can you interpret those values for me - which one is using glibc
(which version)?

> My questions are:
> 1. Are you aware of the speed differences between the ARM and glibc speeds?

I personally not but I hope others will chime in.

> 2. Are there any glibc options or new releases which will speed up the
> library?

Which glibc version are you using? 

> 3. Do you know of any alternatives to glibc which are faster?

No.

Please note that your test uses float variables for the test and uses:
        val = (10*log10(power/(fsc * fsc))-(46*3.01)-3.65-powerCutBack + 
initGain - gain);

Please use log10f so that the calculations is done in float and not in
double.  Does this help?

Andreas
-- 
 Andreas Jaeger
  SuSE Labs address@hidden
   private address@hidden
    http://www.suse.de/~aj