qbfsat: Add bisection mode and make it the default.
authorAlberto Gonzalez <boqwxp@airmail.cc>
Sat, 25 Apr 2020 04:12:02 +0000 (04:12 +0000)
committerAlberto Gonzalez <boqwxp@airmail.cc>
Sat, 23 May 2020 00:53:09 +0000 (00:53 +0000)
Also adds `-nooptimize` and reorganizes `qbfsat.cc` a bit.

passes/sat/qbfsat.cc

index d99ca1b533eb3c11dc1b682df04620073b611f61..0484b57b321aaf69e717a701f3b203c2707210f4 100644 (file)
@@ -19,6 +19,7 @@
 
 #include "kernel/yosys.h"
 #include "kernel/celltypes.h"
+#include "kernel/consteval.h"
 #include "kernel/log.h"
 #include "kernel/rtlil.h"
 #include "kernel/register.h"
@@ -43,13 +44,13 @@ struct QbfSolutionType {
        dict<std::string, std::string> hole_to_value;
        bool sat;
        bool unknown; //true if neither 'sat' nor 'unsat'
-       bool success; //true if exit code 0
 
-       QbfSolutionType() : sat(false), unknown(true), success(false) {}
+       QbfSolutionType() : sat(false), unknown(true) {}
 };
 
 struct QbfSolveOptions {
        bool specialize, specialize_from_file, write_solution, nocleanup, dump_final_smt2, assume_outputs, assume_neg;
+       bool nooptimize, nobisection;
        bool sat, unsat, show_smtbmc;
        std::string specialize_soln_file;
        std::string write_soln_soln_file;
@@ -57,12 +58,14 @@ struct QbfSolveOptions {
        size_t argidx;
        QbfSolveOptions() : specialize(false), specialize_from_file(false), write_solution(false),
                        nocleanup(false), dump_final_smt2(false), assume_outputs(false), assume_neg(false),
-                       sat(false), unsat(false), show_smtbmc(false), argidx(0) {};
+                       nooptimize(false), nobisection(false), sat(false), unsat(false), show_smtbmc(false),
+                       argidx(0) {};
 };
 
 void recover_solution(QbfSolutionType &sol) {
        YS_REGEX_TYPE sat_regex = YS_REGEX_COMPILE("Status: PASSED");
        YS_REGEX_TYPE unsat_regex = YS_REGEX_COMPILE("Solver Error.*model is not available");
+       YS_REGEX_TYPE memout_regex = YS_REGEX_COMPILE("Solver Error:.*error \"out of memory\"");
        YS_REGEX_TYPE hole_value_regex = YS_REGEX_COMPILE_WITH_SUBS("Value for anyconst in [a-zA-Z0-9_]* \\(([^:]*:[^\\)]*)\\): (.*)");
 #ifndef NDEBUG
        YS_REGEX_TYPE hole_loc_regex = YS_REGEX_COMPILE("[^:]*:[0-9]+.[0-9]+-[0-9]+.[0-9]+");
@@ -86,6 +89,10 @@ void recover_solution(QbfSolutionType &sol) {
                        sat_regex_found = true;
                else if (YS_REGEX_NS::regex_search(x, unsat_regex))
                        unsat_regex_found = true;
+               else if (YS_REGEX_NS::regex_search(x, memout_regex)) {
+                       sol.unknown = true;
+                       log_warning("solver ran out of memory\n");
+               }
        }
 #ifndef NDEBUG
        log_assert(!sol.unknown && sol.sat? sat_regex_found : true);
@@ -107,6 +114,40 @@ dict<std::string, std::string> get_hole_loc_name_map(RTLIL::Module *module, cons
        return hole_loc_to_name;
 }
 
+pool<std::string> validate_design_and_get_inputs(RTLIL::Module *module, const QbfSolveOptions &opt) {
+       bool found_input = false;
+       bool found_hole = false;
+       bool found_1bit_output = false;
+       bool found_assert_assume = false;
+       pool<std::string> input_wires;
+       for (auto wire : module->wires()) {
+               if (wire->port_input) {
+                       found_input = true;
+                       input_wires.insert(wire->name.str());
+               }
+               if (wire->port_output && wire->width == 1)
+                       found_1bit_output = true;
+       }
+       for (auto cell : module->cells()) {
+               if (cell->type == "$allconst")
+                       found_input = true;
+               if (cell->type == "$anyconst")
+                       found_hole = true;
+               if (cell->type.in("$assert", "$assume"))
+                       found_assert_assume = true;
+       }
+       if (!found_input)
+               log_cmd_error("Can't perform QBF-SAT on a miter with no inputs!\n");
+       if (!found_hole)
+               log_cmd_error("Did not find any existentially-quantified variables. Use 'sat' instead.\n");
+       if (!found_1bit_output && !found_assert_assume)
+               log_cmd_error("Did not find any single-bit outputs or $assert/$assume cells. Is this a miter circuit?\n");
+       if (!found_assert_assume && !opt.assume_outputs)
+               log_cmd_error("Did not find any $assert/$assume cells. Single-bit outputs were found, but `-assume-outputs` was not specified.\n");
+
+       return input_wires;
+}
+
 void write_solution(RTLIL::Module *module, const QbfSolutionType &sol, const std::string &file) {
        std::ofstream fout(file.c_str());
        if (!fout)
@@ -164,7 +205,7 @@ void specialize_from_file(RTLIL::Module *module, const std::string &file) {
        }
 }
 
-void specialize(RTLIL::Module *module, const QbfSolutionType &sol) {
+void specialize(RTLIL::Module *module, const QbfSolutionType &sol, bool quiet = false) {
        dict<std::string, std::string> hole_loc_to_name = get_hole_loc_name_map(module, sol);
        pool<RTLIL::Cell *> anyconsts_to_remove;
        for (auto cell : module->cells())
@@ -189,7 +230,8 @@ void specialize(RTLIL::Module *module, const QbfSolutionType &sol) {
                log_assert(wire->width > 0 && GetSize(hole_value) == wire->width);
 #endif
 
-               log("Specializing %s with %s = %d'b%s.\n", module->name.c_str(), hole_name.c_str(), wire->width, hole_value.c_str());
+               if (!quiet)
+                       log("Specializing %s with %s = %d'b%s.\n", module->name.c_str(), hole_name.c_str(), wire->width, hole_value.c_str());
                std::vector<RTLIL::SigBit> value_bv;
                value_bv.reserve(wire->width);
                for (char c : hole_value)
@@ -219,7 +261,6 @@ void dump_model(RTLIL::Module *module, const QbfSolutionType &sol) {
                        value_bv.emplace_back(c == '1'? RTLIL::S1 : RTLIL::S0);
                std::reverse(value_bv.begin(), value_bv.end());
        }
-
 }
 
 void allconstify_inputs(RTLIL::Module *module, const pool<std::string> &input_wires) {
@@ -280,84 +321,153 @@ void assume_miter_outputs(RTLIL::Module *module, const QbfSolveOptions &opt) {
        module->addAssume("$assume_qbfsat_miter_outputs", wires_to_assume[0], RTLIL::S1);
 }
 
-QbfSolutionType qbf_solve(RTLIL::Module *mod, const QbfSolveOptions &opt) {
+QbfSolutionType call_qbf_solver(RTLIL::Module *mod, const QbfSolveOptions &opt, const std::string &tempdir_name, const bool quiet = false, const int iter_num = 0) {
+       //Execute and capture stdout from `yosys-smtbmc -s z3 -t 1 -g --binary [--dump-smt2 <file>]`
        QbfSolutionType ret;
        const std::string yosys_smtbmc_exe = proc_self_dirname() + "yosys-smtbmc";
+       const std::string smt2_command = "write_smt2 -stbv -wires " + tempdir_name + "/problem" + (iter_num != 0? stringf("%d", iter_num) : "") + ".smt2";
+       const std::string smtbmc_cmd = yosys_smtbmc_exe + " -s z3 -t 1 -g --binary " + (opt.dump_final_smt2? "--dump-smt2 " + opt.dump_final_smt2_file + " " : "") + tempdir_name + "/problem" + (iter_num != 0? stringf("%d", iter_num) : "") + ".smt2 2>&1";
        const std::string smtbmc_warning = "z3: WARNING:";
        const bool show_smtbmc = opt.show_smtbmc;
 
-       const std::string tempdir_name = make_temp_dir("/tmp/yosys-z3-XXXXXX");
-       const std::string smt2_command = "write_smt2 -stbv -wires " + tempdir_name + "/problem.smt2";
-#ifndef NDEBUG
-       log_assert(mod->design != nullptr);
-#endif
        Pass::call(mod->design, smt2_command);
-       log_header(mod->design, "Solving QBF-SAT problem.\n");
 
-       //Execute and capture stdout from `yosys-smtbmc -s z3 -t 1 -g --binary [--dump-smt2 <file>]`
-       {
-               const std::string cmd = yosys_smtbmc_exe + " -s z3 -t 1 -g --binary " + (opt.dump_final_smt2? "--dump-smt2 " + opt.dump_final_smt2_file + " " : "") + tempdir_name + "/problem.smt2 2>&1";
-               auto process_line = [&ret, &smtbmc_warning, &show_smtbmc](const std::string &line) {
-                       ret.stdout_lines.push_back(line.substr(0, line.size()-1)); //don't include trailing newline
-                       auto warning_pos = line.find(smtbmc_warning);
-                       if (warning_pos != std::string::npos)
-                               log_warning("%s", line.substr(warning_pos + smtbmc_warning.size() + 1).c_str());
-                       else
-                               if (show_smtbmc)
-                                       log("smtbmc output: %s", line.c_str());
-               };
-
-               log("Launching \"%s\".\n", cmd.c_str());
-               int retval = run_command(cmd, process_line);
-               if (retval == 0) {
-                       ret.sat = true;
-                       ret.unknown = false;
-               } else if (retval == 1) {
-                       ret.sat = false;
-                       ret.unknown = false;
-               }
+       auto process_line = [&ret, &smtbmc_warning, &show_smtbmc, &quiet](const std::string &line) {
+               ret.stdout_lines.push_back(line.substr(0, line.size()-1)); //don't include trailing newline
+               auto warning_pos = line.find(smtbmc_warning);
+               if (warning_pos != std::string::npos)
+                       log_warning("%s", line.substr(warning_pos + smtbmc_warning.size() + 1).c_str());
+               else
+                       if (show_smtbmc && !quiet)
+                               log("smtbmc output: %s", line.c_str());
+       };
+       log_header(mod->design, "Solving QBF-SAT problem.\n");
+       if (!quiet) log("Launching \"%s\".\n", smtbmc_cmd.c_str());
+       int retval = run_command(smtbmc_cmd, process_line);
+       if (retval == 0) {
+               ret.sat = true;
+               ret.unknown = false;
+       } else if (retval == 1) {
+               ret.sat = false;
+               ret.unknown = false;
        }
 
-       if(!opt.nocleanup)
-               remove_directory(tempdir_name);
-
        recover_solution(ret);
-
        return ret;
 }
 
-pool<std::string> validate_design_and_get_inputs(RTLIL::Module *module, const QbfSolveOptions &opt) {
-       bool found_input = false;
-       bool found_hole = false;
-       bool found_1bit_output = false;
-       bool found_assert_assume = false;
-       pool<std::string> input_wires;
-       for (auto wire : module->wires()) {
-               if (wire->port_input) {
-                       found_input = true;
-                       input_wires.insert(wire->name.str());
-               }
-               if (wire->port_output && wire->width == 1)
-                       found_1bit_output = true;
+QbfSolutionType qbf_solve(RTLIL::Module *mod, const QbfSolveOptions &opt) {
+       QbfSolutionType ret, best_soln;
+       const std::string tempdir_name = make_temp_dir("/tmp/yosys-z3-XXXXXX");
+       RTLIL::Module *module = mod;
+       RTLIL::Design *design = module->design;
+       std::string module_name = module->name.str();
+       RTLIL::Wire *wire_to_optimize = nullptr;
+       RTLIL::IdString wire_to_optimize_name;
+       bool maximize = false;
+       log_assert(module->design != nullptr);
+
+       Pass::call(design, "design -push-copy");
+
+       //Replace input wires with wires assigned $allconst cells:
+       pool<std::string> input_wires = validate_design_and_get_inputs(module, opt);
+       allconstify_inputs(module, input_wires);
+       if (opt.assume_outputs)
+               assume_miter_outputs(module, opt);
+
+       //Find the wire to be optimized, if any:
+       for (auto wire : module->wires())
+               if (wire->get_bool_attribute("\\maximize") || wire->get_bool_attribute("\\minimize"))
+                       wire_to_optimize = wire;
+       if (wire_to_optimize != nullptr) {
+               wire_to_optimize_name = wire_to_optimize->name;
+               maximize = wire_to_optimize->get_bool_attribute("\\maximize");
        }
-       for (auto cell : module->cells()) {
-               if (cell->type == "$allconst")
-                       found_input = true;
-               if (cell->type == "$anyconst")
-                       found_hole = true;
-               if (cell->type.in("$assert", "$assume"))
-                       found_assert_assume = true;
+
+       if (opt.nobisection || opt.nooptimize) {
+               if (wire_to_optimize != nullptr && opt.nooptimize) {
+                       wire_to_optimize->set_bool_attribute("\\maximize", false);
+                       wire_to_optimize->set_bool_attribute("\\minimize", false);
+               }
+               ret = call_qbf_solver(module, opt, tempdir_name, false, 0);
+       } else {
+               //Do the iterated bisection method:
+               unsigned int iter_num = 1;
+               unsigned int success = 0;
+               unsigned int failure = 0;
+               unsigned int cur_thresh = 0;
+
+               log_assert(wire_to_optimize != nullptr);
+               log("%s wire \"%s\".\n", (maximize? "Maximizing" : "Minimizing"), log_signal(wire_to_optimize));
+
+               //If maximizing, grow until we get a failure.  Then bisect success and failure.
+               while (failure == 0 || success - failure > 1) {
+                       Pass::call(design, "design -push-copy");
+                       log_header(design, "Preparing QBF-SAT problem.\n");
+
+                       if (cur_thresh != 0) {
+                               //Add thresholding logic (but not on the initial run when we don't have a sense of where to start):
+                               RTLIL::SigSpec comparator = maximize? module->Ge(NEW_ID, module->wire(wire_to_optimize_name), RTLIL::Const(cur_thresh), false)
+                                                                   : module->Le(NEW_ID, module->wire(wire_to_optimize_name), RTLIL::Const(cur_thresh), false);
+
+                               module->addAssume(wire_to_optimize_name.str() + "__threshold", comparator, RTLIL::Const(1, 1));
+                               log("Trying to solve with %s %s %d.\n", wire_to_optimize_name.c_str(), (maximize? ">=" : "<="), cur_thresh);
+                       }
+
+                       ret = call_qbf_solver(module, opt, tempdir_name, false, iter_num);
+                       Pass::call(design, "design -pop");
+                       module = design->module(module_name);
+
+                       if (!ret.unknown && ret.sat) {
+                               Pass::call(design, "design -push-copy");
+                               specialize(module, ret, true);
+
+                               RTLIL::SigSpec wire, value, undef;
+                               RTLIL::SigSpec::parse_sel(wire, design, module, wire_to_optimize_name.str());
+
+                               ConstEval ce(module);
+                               value = wire;
+                               if (!ce.eval(value, undef))
+                                       log_cmd_error("Failed to evaluate signal %s: Missing value for %s.\n", log_signal(wire), log_signal(undef));
+                               log_assert(value.is_fully_const());
+                               success = value.as_const().as_int();
+                               best_soln = ret;
+                               log("Problem is satisfiable with %s = %d.\n", wire_to_optimize_name.c_str(), success);
+                               Pass::call(design, "design -pop");
+                               module = design->module(module_name);
+
+                               //sometimes this happens if we get an 'unknown' or timeout
+                               if (!maximize && success < failure)
+                                       break;
+                               else if (maximize && success > failure)
+                                       break;
+                       } else {
+                               //Treat 'unknown' as UNSAT
+                               failure = cur_thresh;
+                               if (failure == 0) {
+                                       log("Problem is NOT satisfiable.\n");
+                                       break;
+                               }
+                               else
+                                       log("Problem is NOT satisfiable with %s %s %d.\n", wire_to_optimize_name.c_str(), (maximize? ">=" : "<="), failure);
+                       }
+
+                       iter_num++;
+                       cur_thresh = (maximize && failure == 0)? 2 * success //growth
+                                                              : (success + failure) / 2; //bisection
+               }
+               if (success != 0 || failure != 0) {
+                       log("Wire %s is %s at %d.\n", wire_to_optimize_name.c_str(), (maximize? "maximized" : "minimized"), success);
+                       ret = best_soln;
+               }
        }
-       if (!found_input)
-               log_cmd_error("Can't perform QBF-SAT on a miter with no inputs!\n");
-       if (!found_hole)
-               log_cmd_error("Did not find any existentially-quantified variables. Use 'sat' instead.\n");
-       if (!found_1bit_output && !found_assert_assume)
-               log_cmd_error("Did not find any single-bit outputs or $assert/$assume cells. Is this a miter circuit?\n");
-       if (!found_assert_assume && !opt.assume_outputs)
-               log_cmd_error("Did not find any $assert/$assume cells. Single-bit outputs were found, but `-assume-outputs` was not specified.\n");
 
-       return input_wires;
+       if(!opt.nocleanup)
+               remove_directory(tempdir_name);
+
+       Pass::call(design, "design -pop");
+
+       return ret;
 }
 
 QbfSolveOptions parse_args(const std::vector<std::string> &args) {
@@ -379,6 +489,14 @@ QbfSolveOptions parse_args(const std::vector<std::string> &args) {
                        opt.assume_neg = true;
                        continue;
                }
+               else if (args[opt.argidx] == "-nooptimize") {
+                       opt.nooptimize = true;
+                       continue;
+               }
+               else if (args[opt.argidx] == "-nobisection") {
+                       opt.nobisection = true;
+                       continue;
+               }
                else if (args[opt.argidx] == "-sat") {
                        opt.sat = true;
                        continue;
@@ -477,6 +595,17 @@ struct QbfSatPass : public Pass {
                log("        negative polarity signals and should always be low, for example like the\n");
                log("        miters created with the `miter` command.\n");
                log("\n");
+               log("    -nooptimize\n");
+               log("        Ignore \"\\minimize\" and \"\\maximize\" attributes, do not emit \"(maximize)\" or\n");
+               log("        \"(minimize)\" in the SMTLIBv2, and generally make no attempt to optimize anything.\n");
+               log("\n");
+               log("    -nobisection\n");
+               log("        If a wire is marked with the \"\\minimize\" or \"\\maximize\" attribute, do not\n");
+               log("        attempt to optimize that value with the default iterated solving and threshold\n");
+               log("        bisection approach. Instead, have yosys-smtbmc emit a \"(minimize)\" or \"(maximize)\"\n");
+               log("        command in the SMTLIBv2 output and hope that the solver supports optimizing\n");
+               log("        quantified bitvector problems.\n");
+               log("\n");
                log("    -sat\n");
                log("        Generate an error if the solver does not return \"sat\".\n");
                log("\n");
@@ -519,26 +648,16 @@ struct QbfSatPass : public Pass {
                if (!opt.specialize_from_file) {
                        //Save the design to restore after modiyfing the current module.
                        std::string module_name = module->name.str();
-                       Pass::call(design, "design -push-copy");
-
-                       //Replace input wires with wires assigned $allconst cells.
-                       pool<std::string> input_wires = validate_design_and_get_inputs(module, opt);
-                       allconstify_inputs(module, input_wires);
-                       if (opt.assume_outputs)
-                               assume_miter_outputs(module, opt);
 
                        QbfSolutionType ret = qbf_solve(module, opt);
-                       Pass::call(design, "design -pop");
                        module = design->module(module_name);
-
-                       if (ret.unknown)
+                       if (ret.unknown) {
                                log_warning("solver did not give an answer\n");
-                       else if (ret.sat)
+                               if (opt.sat || opt.unsat)
+                                       log_cmd_error("expected problem to be %s\n", opt.sat? "SAT" : "UNSAT");
+                       }
+                       else if (ret.sat) {
                                print_qed();
-                       else
-                               print_proof_failed();
-
-                       if(!ret.unknown && ret.sat) {
                                if (opt.write_solution) {
                                        write_solution(module, ret, opt.write_soln_soln_file);
                                }
@@ -550,10 +669,11 @@ struct QbfSatPass : public Pass {
                                if (opt.unsat)
                                        log_cmd_error("expected problem to be UNSAT\n");
                        }
-                       else if (!ret.unknown && !ret.sat && opt.sat)
-                               log_cmd_error("expected problem to be SAT\n");
-                       else if (ret.unknown && (opt.sat || opt.unsat))
-                               log_cmd_error("expected problem to be %s\n", opt.sat? "SAT" : "UNSAT");
+                       else {
+                               print_proof_failed();
+                               if (opt.sat)
+                                       log_cmd_error("expected problem to be SAT\n");
+                       }
                } else
                        specialize_from_file(module, opt.specialize_soln_file);
                log_pop();