Re: [ECOS] libc-time-clock test doesn't seem to be written correctly??

[Jonathan Larmour <jifl at eCosCentric dot com>]

Brij Bihari Pandey wrote:
> Hi Jonathan,
>
> [snip] 
>
> > > 40%,  because err(100*(3-2)/2) > TOLERANCE(40).
> >
> > [snip]
> > I suppose it's possible with small values, although I've never seen a port 
> > do this in practice - the processor would have to be slow and the clock 
> > rate fast.
>
> Sure. Had there been some port like that in practice, someone should have
> surely mentioned that on the list. I pointed out issues with test so that
> newbies on hardwares don't break their heads looking for problems, perturbed by
> test FAIL messages. Possibly I would have - how could there be problem with the
> test, wouldn't anyone on list have mentioned it earlier, if it was so?

Not necessarily I suppose. But there would probably have been something in 
the wide variety of hardware that used to exist in the Red Hat test farm.

> > I would accept a patch on those lines; or more precisely, something that 
> > checks for the %tolerance, and then checks if the difference is greater 
> > than an absolute amount. A fudge factor really :-). That will allow minor 
> > anomalies to pass, as well as small values.
> >
> > Send me a patch like that and I'll review it.
>
> Will do as you ask for. It looks like maximum 2-3 lines of code insertion.
> Plain diff of patched code vs original code will do?

cvs diff -u5 -p is preferred. Mail it to ecos-patches@sources.redhat.com

> > If the underlying clock is correctly periodic, the return value of clock() 
> > should change similarly periodically. And counting how long it takes to do 
> > this in a for loop in a consistent way should therefore result in similar 
> > numbers.
>
> Do you mean to say that the time taken between 1st iteration of for-loop in two
> consecutive calls of clock_loop in the test will be same or is it something
> different that I am not getting here? First one is obvious enough, always
> supposed to happen.

The for loop counts how long it takes for the return value of clock() to 
change, that's all. Since the code is looped over in a consistent way, how 
far the for loop counts should be roughly the same if you run it again and 
again.

Jifl
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