--- layout: fc_discuss_archives title: Message 32 from Frama-C-discuss on February 2014 ---
Hello, > Is there any possibility to make this program verifiable with Alt-Ergo? Yes ... with option *-max-split -1* More precisely, the decision procedure of linear integer arithmetic in Alt-Ergo uses bounds inference and interval calculus [1]. It is based on the following claims: (a) If all the affine forms of the problem are unbounded, we are sure that this problem has a solution. (b) If some affine form has a lower (integer) bound *L* and an upper bound *U*, Alt-Ergo may try all the possible integer values in [| L , U|] to see if there exists a solution that satisfies these bounds. In practice, when the intervals *[| L , U|]* are huge, Alt-Ergo may spend a lot of time in (b), which makes it "unfair". So, we put a "max-split" limit in this part of Alt-Ergo to prevent it from "diverging". The option -max-split -1 deactivates this limit. [1] A Simplex-Based Extension of Fourier-Motzkin for Solving Linear Integer Arithmetic: F. Bobot, S. Conchon, E. Contejean, M. Iguernelala, A. Mahboubi, A. Mebsout, G. Melquiond - Mohamed. ---- Senior R&D Engineer, OCamlPro Research Associate, VALS team, LRI. http://www.iguer.info Le 16/02/2014 22:01, Dharmalingam Ganesan a ?crit : > Hi, > > For the attached program, all the properties were proved by Z3 but Alt-Ergo timeout/Unknown for loop invariants. > > If I replace UINT_MAX by a small constant, say 100, then Alt-Ergo was also able to prove if I substitute UINT_MAX by 1000. > > Is there any possibility to make this program verifiable with Alt-Ergo? > > Here is my log for Z3 and Alt-Ergo: > > > [formal_verification]$ frama-c -wp -wp-rte -pp-annot -wp-timeout 25 -wp-proof=z3 c_nullify.c > [kernel] preprocessing with "gcc -C -E -I. -dD c_nullify.c" > [wp] Running WP plugin... > [wp] Collecting axiomatic usage > [rte] annotating function C_nullify > [rte] annotating function main > [wp] 13 goals scheduled > [wp] [Qed] Goal typed_C_nullify_loop_inv_established : Valid > [wp] [Qed] Goal typed_C_nullify_loop_assign_part1 : Valid > [wp] [Z3] Goal typed_C_nullify_assert_rte_unsigned_overflow : Valid (10ms) > [wp] [Z3] Goal typed_C_nullify_assert_rte_mem_access : Valid (10ms) > [wp] [Z3] Goal typed_C_nullify_loop_inv_preserved : Valid (10ms) > [wp] [Z3] Goal typed_C_nullify_loop_assign_part2 : Valid (10ms) > [wp] [Qed] Goal typed_C_nullify_assign_part1 : Valid > [wp] [Qed] Goal typed_C_nullify_loop_term_decrease : Valid > [wp] [Qed] Goal typed_C_nullify_loop_term_positive : Valid > [wp] [Qed] Goal typed_main_call_C_nullify_pre : Valid > [wp] [Qed] Goal typed_main_call_C_nullify_pre_2 : Valid > [wp] [Z3] Goal typed_C_nullify_assign_part2 : Valid > [wp] [Z3] Goal typed_C_nullify_loop_assign_part3 : Valid (20ms) > > > > [formal_verification]$ frama-c -wp -wp-rte -pp-annot -wp-timeout 100 -wp-proof=alt-ergo c_nullify.c > [kernel] preprocessing with "gcc -C -E -I. -dD c_nullify.c" > [wp] Running WP plugin... > [wp] Collecting axiomatic usage > [rte] annotating function C_nullify > [rte] annotating function main > [wp] 13 goals scheduled > [wp] [Qed] Goal typed_C_nullify_loop_inv_established : Valid > [wp] [Qed] Goal typed_C_nullify_loop_assign_part1 : Valid > [wp] [Alt-Ergo] Goal typed_C_nullify_assert_rte_unsigned_overflow : Valid (13) > [wp] [Alt-Ergo] Goal typed_C_nullify_assert_rte_mem_access : Valid (20ms) (22) > [wp] [Qed] Goal typed_C_nullify_assign_part1 : Valid > [wp] [Alt-Ergo] Goal typed_C_nullify_loop_assign_part2 : Valid (20ms) (23) > [wp] [Qed] Goal typed_C_nullify_loop_term_decrease : Valid > [wp] [Alt-Ergo] Goal typed_C_nullify_loop_assign_part3 : Valid (Qed:4ms) (24ms) (31) > [wp] [Qed] Goal typed_C_nullify_loop_term_positive : Valid > [wp] [Alt-Ergo] Goal typed_C_nullify_assign_part2 : Valid (16ms) (16) > [wp] [Qed] Goal typed_main_call_C_nullify_pre : Valid > [wp] [Qed] Goal typed_main_call_C_nullify_pre_2 : Valid > [wp] [Alt-Ergo] Goal typed_C_nullify_loop_inv_preserved : Unknown (Qed:4ms) (12s) > > > > Thanks, > Dharma > > > _______________________________________________ > Frama-c-discuss mailing list > Frama-c-discuss at lists.gforge.inria.fr > http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/frama-c-discuss -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.gforge.inria.fr/pipermail/frama-c-discuss/attachments/20140217/eb1588ad/attachment.html>