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,
>
> I have few doubts about
> packages/language/c/libc/time/current/tests/clock.c Doesn't look like
> that this test will function correctly (as desired by test writers).
>
> - It is quite possible that clock_loop returns "0", as the code there
> breaks out in the first iteration of for-loop and it happens more or
> less consistently in all the calls to clock_loop. In this case, the
> mean value in main will turn out to be zero causing division-by-zero in
> err calculation.

It's true that there does seem to be an assumption there, although that 
assumption has been right before because each call to clock_loop will 
follow the previous one faster than clock() will increment on virtually 
all processors. I'll fix it with:
        // use mean+1 as divisor to avoid div-by-zero
        err = (100 * my_abs(ctrs[i]-mean)) / (mean+1);

> Another related thought - shouldn't the analysis of going through valid
>  results and comparing against average -- be done using floating point
>  arithmetic for mean/err computation and comparision?

Why bother?

> - Should test fail on first err value, that is not within TOLERANCE? It
> may be better if failure-tolerance (another parameter) is taken on 
> number-of-samples not within TOLERANCE limit, to decide the
> test-failure.

If the system disappears into the middle of nowhere for a long time before 
coming back even once, then something needs investigating. It may be 
alright, but that's not up to this test to know.

> What I gather from the comments in the test, that it tests -
> - if clock is working or not, 
> - if it is stable (PASS message) or not.
>
> Am I right in my understading the purpose of this test?

Yes.

> Though I don't quite get - - What is meant by stability of clock? - In
> what way the nature of test ensures it is testing stability of clock?

Roughly equal period between clock increments.

Jifl
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