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/********************* */
/*! \file bitvectors_and_arrays.cpp
** \verbatim
** Top contributors (to current version):
** Liana Hadarean
** This file is part of the CVC4 project.
** Copyright (c) 2009-2020 by the authors listed in the file AUTHORS
** in the top-level source directory) and their institutional affiliations.
** All rights reserved. See the file COPYING in the top-level source
** directory for licensing information.\endverbatim
**
** \brief A simple demonstration of the solving capabilities of the CVC4
** bit-vector and array solvers.
**
**/
#include <iostream>
#include <cmath>
#include <cvc4/cvc4.h>
using namespace std;
using namespace CVC4;
int main() {
ExprManager em;
SmtEngine smt(&em);
smt.setOption("produce-models", true); // Produce Models
smt.setOption("output-language", "smtlib"); // output-language
smt.setLogic("QF_AUFBV"); // Set the logic
// Consider the following code (where size is some previously defined constant):
//
//
// Assert (current_array[0] > 0);
// for (unsigned i = 1; i < k; ++i) {
// current_array[i] = 2 * current_array[i - 1];
// Assert (current_array[i-1] < current_array[i]);
// }
//
// We want to check whether the assertion in the body of the for loop holds
// throughout the loop.
// Setting up the problem parameters
unsigned k = 4; // number of unrollings (should be a power of 2)
unsigned index_size = log2(k); // size of the index
// Types
Type elementType = em.mkBitVectorType(32);
Type indexType = em.mkBitVectorType(index_size);
Type arrayType = em.mkArrayType(indexType, elementType);
// Variables
Expr current_array = em.mkVar("current_array", arrayType);
// Making a bit-vector constant
Expr zero = em.mkConst(BitVector(index_size, 0u));
// Asserting that current_array[0] > 0
Expr current_array0 = em.mkExpr(kind::SELECT, current_array, zero);
Expr current_array0_gt_0 = em.mkExpr(kind::BITVECTOR_SGT, current_array0, em.mkConst(BitVector(32, 0u)));
smt.assertFormula(current_array0_gt_0);
// Building the assertions in the loop unrolling
Expr index = em.mkConst(BitVector(index_size, 0u));
Expr old_current = em.mkExpr(kind::SELECT, current_array, index);
Expr two = em.mkConst(BitVector(32, 2u));
std::vector<Expr> assertions;
for (unsigned i = 1; i < k; ++i) {
index = em.mkConst(BitVector(index_size, Integer(i)));
Expr new_current = em.mkExpr(kind::BITVECTOR_MULT, two, old_current);
// current[i] = 2 * current[i-1]
current_array = em.mkExpr(kind::STORE, current_array, index, new_current);
// current[i-1] < current [i]
Expr current_slt_new_current = em.mkExpr(kind::BITVECTOR_SLT, old_current, new_current);
assertions.push_back(current_slt_new_current);
old_current = em.mkExpr(kind::SELECT, current_array, index);
}
Expr query = em.mkExpr(kind::NOT, em.mkExpr(kind::AND, assertions));
cout << "Asserting " << query << " to CVC4 " << endl;
smt.assertFormula(query);
cout << "Expect sat. " << endl;
cout << "CVC4: " << smt.checkSat(em.mkConst(true)) << endl;
// Getting the model
cout << "The satisfying model is: " << endl;
cout << " current_array = " << smt.getValue(current_array) << endl;
cout << " current_array[0] = " << smt.getValue(current_array0) << endl;
return 0;
}
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