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[Frama-c-discuss] [Jessie] loop invariant

Hi,

We have run the example as suggested by Claude
(http://proval.lri.fr/gallery/ScalarProduct.en.html).

We used the example annotations in our code (attached) and the all VCs
were proved.

However, we have some doubts:

1. We have used the lemma bound_int_to_real but we did not understand
how it works.
Why the define NMAXR is used?

2. The variable j used in the loop was global in the legacy source
code. However, the loop invariant  was not proved (loop invariant
\abs(p - sum(x,j)) <= j * BOUND).
  We changed the variable j to local and the loop invariant was proved.
  Does not the loop invariant work with global variable?

Best regards,
Nanci, Luciana e Rovedy




2013/9/7 Claude Marche <Claude.Marche at inria.fr>
>
>
>
> On 09/07/2013 10:56 AM, Claude Marche wrote:
>>>
>>> Alternatively, you can force the computation into float in sum
>>> by modifying your axiom:
>>>    @   axiom sum2{L} :
>>>    @     \forall float *t, integer i, j;
>>>    @       sum(t,i,j+1) == (float)(sum(t,i,j) + t[j]);
>>> But this is not a very good idea IMHO: as floating point addition is
>
>
> A very bad idea indeed.
>
> - claude
>
>
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