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/******************************************************************************
* Top contributors (to current version):
* Aina Niemetz, Liana Hadarean, Makai Mann
*
* This file is part of the cvc5 project.
*
* Copyright (c) 2009-2021 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.
* ****************************************************************************
*
* A simple demonstration of the solving capabilities of the cvc5
* bit-vector solver.
*
*/
import io.github.cvc5.api.*;
import java.util.*;
public class BitVectorsAndArrays
{
private static int log2(int n)
{
return (int) Math.round(Math.log(n) / Math.log(2));
}
public static void main(String[] args) throws CVC5ApiException
{
Solver slv = new Solver();
slv.setOption("produce-models", "true"); // Produce Models
slv.setOption("output-language", "smtlib"); // output-language
slv.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
int k = 4; // number of unrollings (should be a power of 2)
int index_size = log2(k); // size of the index
// Sorts
Sort elementSort = slv.mkBitVectorSort(32);
Sort indexSort = slv.mkBitVectorSort(index_size);
Sort arraySort = slv.mkArraySort(indexSort, elementSort);
// Variables
Term current_array = slv.mkConst(arraySort, "current_array");
// Making a bit-vector constant
Term zero = slv.mkBitVector(index_size, 0);
// Asserting that current_array[0] > 0
Term current_array0 = slv.mkTerm(Kind.SELECT, current_array, zero);
Term current_array0_gt_0 =
slv.mkTerm(Kind.BITVECTOR_SGT, current_array0, slv.mkBitVector(32, 0));
slv.assertFormula(current_array0_gt_0);
// Building the assertions in the loop unrolling
Term index = slv.mkBitVector(index_size, 0);
Term old_current = slv.mkTerm(Kind.SELECT, current_array, index);
Term two = slv.mkBitVector(32, 2);
List<Term> assertions = new ArrayList<Term>();
for (int i = 1; i < k; ++i)
{
index = slv.mkBitVector(index_size, i);
Term new_current = slv.mkTerm(Kind.BITVECTOR_MULT, two, old_current);
// current[i] = 2 * current[i-1]
current_array = slv.mkTerm(Kind.STORE, current_array, index, new_current);
// current[i-1] < current [i]
Term current_slt_new_current = slv.mkTerm(Kind.BITVECTOR_SLT, old_current, new_current);
assertions.add(current_slt_new_current);
old_current = slv.mkTerm(Kind.SELECT, current_array, index);
}
Term query = slv.mkTerm(Kind.NOT, slv.mkTerm(Kind.AND, assertions.toArray(new Term[0])));
System.out.println("Asserting " + query + " to cvc5 ");
slv.assertFormula(query);
System.out.println("Expect sat. ");
System.out.println("cvc5: " + slv.checkSatAssuming(slv.mkTrue()));
// Getting the model
System.out.println("The satisfying model is: ");
System.out.println(" current_array = " + slv.getValue(current_array));
System.out.println(" current_array[0] = " + slv.getValue(current_array0));
}
}
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