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smtbmc: Add --track-assumes and --minimize-assumes options

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The --track-assumes option makes smtbmc keep track of which assumptions
were used by the solver when reaching an unsat case and to output that
set of assumptions. This is particularly useful to debug PREUNSAT
failures.

The --minimize-assumes option can be used in addition to --track-assumes
which will cause smtbmc to spend additional solving effort to produce a
minimal set of assumptions that are sufficient to cause the unsat
result.
This commit is contained in:
Jannis Harder 2024-03-07 13:27:03 +01:00
parent e4f11eb0a0
commit 42122e240e
3 changed files with 219 additions and 24 deletions
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87
backends/smt2/smtbmc.py
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@ -57,6 +57,8 @@ keep_going = False
check_witness = False
detect_loops = False
incremental = None
track_assumes = False
minimize_assumes = False
so = SmtOpts()
@ -189,6 +191,15 @@ def help():
--incremental
run in incremental mode (experimental)
--track-assumes
track individual assumptions and report a subset of used
assumptions that are sufficient for the reported outcome. This
can be used to debug PREUNSAT failures as well as to find a
smaller set of sufficient assumptions.
--minimize-assumes
when using --track-assumes, solve for a minimal set of sufficient assumptions.
""" + so.helpmsg())
def usage():
@ -200,7 +211,8 @@ try:
opts, args = getopt.getopt(sys.argv[1:], so.shortopts + "t:higcm:", so.longopts +
["help", "final-only", "assume-skipped=", "smtc=", "cex=", "aig=", "aig-noheader", "yw=", "btorwit=", "presat",
"dump-vcd=", "dump-yw=", "dump-vlogtb=", "vlogtb-top=", "dump-smtc=", "dump-all", "noinfo", "append=",
"smtc-init", "smtc-top=", "noinit", "binary", "keep-going", "check-witness", "detect-loops", "incremental"])
"smtc-init", "smtc-top=", "noinit", "binary", "keep-going", "check-witness", "detect-loops", "incremental",
"track-assumes", "minimize-assumes"])
except:
usage()
@ -289,6 +301,10 @@ for o, a in opts:
elif o == "--incremental":
from smtbmc_incremental import Incremental
incremental = Incremental()
elif o == "--track-assumes":
track_assumes = True
elif o == "--minimize-assumes":
minimize_assumes = True
elif so.handle(o, a):
pass
else:
@ -447,6 +463,9 @@ def get_constr_expr(db, state, final=False, getvalues=False, individual=False):
smt = SmtIo(opts=so)
if track_assumes:
smt.smt2_options[':produce-unsat-assumptions'] = 'true'
if noinfo and vcdfile is None and vlogtbfile is None and outconstr is None:
smt.produce_models = False
@ -1497,6 +1516,44 @@ def get_active_assert_map(step, active):
return assert_map
assume_enables = {}
def declare_assume_enables():
def recurse(mod, path, key_base=()):
for expr, desc in smt.modinfo[mod].assumes.items():
enable = f"|assume_enable {len(assume_enables)}|"
smt.smt2_assumptions[(expr, key_base)] = enable
smt.write(f"(declare-const {enable} Bool)")
assume_enables[(expr, key_base)] = (enable, path, desc)
for cell, submod in smt.modinfo[mod].cells.items():
recurse(submod, f"{path}.{cell}", (mod, cell, key_base))
recurse(topmod, topmod)
if track_assumes:
declare_assume_enables()
def smt_assert_design_assumes(step):
if not track_assumes:
smt_assert_consequent("(|%s_u| s%d)" % (topmod, step))
return
if not assume_enables:
return
def expr_for_assume(assume_key, base=None):
expr, key_base = assume_key
expr_prefix = f"(|{expr}| "
expr_suffix = ")"
while key_base:
mod, cell, key_base = key_base
expr_prefix += f"(|{mod}_h {cell}| "
expr_suffix += ")"
return f"{expr_prefix} s{step}{expr_suffix}"
for assume_key, (enable, path, desc) in assume_enables.items():
smt_assert_consequent(f"(=> {enable} {expr_for_assume(assume_key)})")
states = list()
asserts_antecedent_cache = [list()]
@ -1651,6 +1708,13 @@ def smt_check_sat(expected=["sat", "unsat"]):
smt_forall_assert()
return smt.check_sat(expected=expected)
def report_tracked_assumptions(msg):
if track_assumes:
print_msg(msg)
for key in smt.get_unsat_assumptions(minimize=minimize_assumes):
enable, path, descr = assume_enables[key]
print_msg(f" In {path}: {descr}")
if incremental:
incremental.mainloop()
@ -1664,7 +1728,7 @@ elif tempind:
break
smt_state(step)
smt_assert_consequent("(|%s_u| s%d)" % (topmod, step))
smt_assert_design_assumes(step)
smt_assert_antecedent("(|%s_h| s%d)" % (topmod, step))
smt_assert_antecedent("(not (|%s_is| s%d))" % (topmod, step))
smt_assert_consequent(get_constr_expr(constr_assumes, step))
@ -1707,6 +1771,7 @@ elif tempind:
else:
print_msg("Temporal induction successful.")
report_tracked_assumptions("Used assumptions:")
retstatus = "PASSED"
break
@ -1732,7 +1797,7 @@ elif covermode:
while step < num_steps:
smt_state(step)
smt_assert_consequent("(|%s_u| s%d)" % (topmod, step))
smt_assert_design_assumes(step)
smt_assert_antecedent("(|%s_h| s%d)" % (topmod, step))
smt_assert_consequent(get_constr_expr(constr_assumes, step))
@ -1753,6 +1818,7 @@ elif covermode:
smt_assert("(distinct (covers_%d s%d) #b%s)" % (coveridx, step, "0" * len(cover_desc)))
if smt_check_sat() == "unsat":
report_tracked_assumptions("Used assumptions:")
smt_pop()
break
@ -1761,13 +1827,14 @@ elif covermode:
print_msg("Appending additional step %d." % i)
smt_state(i)
smt_assert_antecedent("(not (|%s_is| s%d))" % (topmod, i))
smt_assert_consequent("(|%s_u| s%d)" % (topmod, i))
smt_assert_design_assumes(i)
smt_assert_antecedent("(|%s_h| s%d)" % (topmod, i))
smt_assert_antecedent("(|%s_t| s%d s%d)" % (topmod, i-1, i))
smt_assert_consequent(get_constr_expr(constr_assumes, i))
print_msg("Re-solving with appended steps..")
if smt_check_sat() == "unsat":
print("%s Cannot appended steps without violating assumptions!" % smt.timestamp())
report_tracked_assumptions("Conflicting assumptions:")
found_failed_assert = True
retstatus = "FAILED"
break
@ -1823,7 +1890,7 @@ else: # not tempind, covermode
retstatus = "PASSED"
while step < num_steps:
smt_state(step)
smt_assert_consequent("(|%s_u| s%d)" % (topmod, step))
smt_assert_design_assumes(step)
smt_assert_antecedent("(|%s_h| s%d)" % (topmod, step))
smt_assert_consequent(get_constr_expr(constr_assumes, step))
@ -1853,7 +1920,7 @@ else: # not tempind, covermode
if step+i < num_steps:
smt_state(step+i)
smt_assert_antecedent("(not (|%s_is| s%d))" % (topmod, step+i))
smt_assert_consequent("(|%s_u| s%d)" % (topmod, step+i))
smt_assert_design_assumes(step + i)
smt_assert_antecedent("(|%s_h| s%d)" % (topmod, step+i))
smt_assert_antecedent("(|%s_t| s%d s%d)" % (topmod, step+i-1, step+i))
smt_assert_consequent(get_constr_expr(constr_assumes, step+i))
@ -1867,7 +1934,8 @@ else: # not tempind, covermode
print_msg("Checking assumptions in steps %d to %d.." % (step, last_check_step))
if smt_check_sat() == "unsat":
print("%s Assumptions are unsatisfiable!" % smt.timestamp())
print_msg("Assumptions are unsatisfiable!")
report_tracked_assumptions("Conficting assumptions:")
retstatus = "PREUNSAT"
break
@ -1920,13 +1988,14 @@ else: # not tempind, covermode
print_msg("Appending additional step %d." % i)
smt_state(i)
smt_assert_antecedent("(not (|%s_is| s%d))" % (topmod, i))
smt_assert_consequent("(|%s_u| s%d)" % (topmod, i))
smt_assert_design_assumes(i)
smt_assert_antecedent("(|%s_h| s%d)" % (topmod, i))
smt_assert_antecedent("(|%s_t| s%d s%d)" % (topmod, i-1, i))
smt_assert_consequent(get_constr_expr(constr_assumes, i))
print_msg("Re-solving with appended steps..")
if smt_check_sat() == "unsat":
print("%s Cannot append steps without violating assumptions!" % smt.timestamp())
print_msg("Cannot append steps without violating assumptions!")
report_tracked_assumptions("Conflicting assumptions:")
retstatus = "FAILED"
break
print_anyconsts(step)