Frama-C-discuss mailing list archives

This page gathers the archives of the old Frama-C-discuss archives, that was hosted by Inria's gforge before its demise at the end of 2020. To search for mails newer than September 2020, please visit the page of the new mailing list on Renater.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Frama-c-discuss] floating-point examples

I'm looking for some simple, interesting floating-point examples that can be proved with Frama-C+Jessie.  Here is a good example from the ACSL manual:

/*@ requires \abs(\exact(x)) <= 0x1p-5;
  @ requires \round_error(x) <= 0x1p-20;
  @ ensures \abs(\exact(\result) - \cos(\exact(x))) <= 0x1p-24;
  @ ensures \round_error(\result) <= \round_error(x) + 0x3p-24;
  @*/
float cosine(float x) {
  return 1.0f - x * x * 0.5f;
}

However, I can't get any of the theorem provers (CVC3, Z3, Alt-Ergo, Gappa, Simplify) to prove either of the generated VCs.  (For all I know, the function may not even satisfy the contract.)  Does anyone know of any examples similar to this that can be proved, or have ideas on how to handle this example?
Thanks in advance!