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https://github.com/AdaCore/cvc5.git
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7d16d25dc9
Fixes #2846. One of the challenges of the Java bindings is that the garbage collector can delete unused objects at any time in any order. This is an issue with CVC4's API because we require all `Expr`s to be deleted before the corresponding `ExprManager`. In the past, we were using `NewGlobalRef`/`DeleteGlobalRef` on the wrapper object of `ExprManager`. The problem is that we can have multiple instances of the wrapper that internally all refer to the same `ExprManager`. This commit implements a different approach where the Java wrappers hold an explicit reference to the `ExprManager`. The commit also removes some unused or unimportant API bits from the bindings.
98 lines
3.7 KiB
Java
98 lines
3.7 KiB
Java
/********************* */
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/*! \file BitVectorsAndArrays.java
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** \verbatim
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** Top contributors (to current version):
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** Morgan Deters, Liana Hadarean, Andres Noetzli
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** This file is part of the CVC4 project.
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** Copyright (c) 2009-2020 by the authors listed in the file AUTHORS
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** in the top-level source directory) and their institutional affiliations.
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** All rights reserved. See the file COPYING in the top-level source
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** directory for licensing information.\endverbatim
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**
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** \brief A simple demonstration of the solving capabilities of the CVC4
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** bit-vector and array solvers.
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**
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**/
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import edu.stanford.CVC4.*;
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import java.util.*;
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public class BitVectorsAndArrays {
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private static int log2(int n) {
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return (int) Math.round(Math.log(n) / Math.log(2));
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}
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public static void main(String[] args) {
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System.loadLibrary("cvc4jni");
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ExprManager em = new ExprManager();
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SmtEngine smt = new SmtEngine(em);
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smt.setOption("produce-models", new SExpr(true)); // Produce Models
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smt.setOption("output-language", new SExpr("smtlib")); // output-language
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smt.setLogic("QF_AUFBV"); // Set the logic
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// Consider the following code (where size is some previously defined constant):
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//
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//
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// Assert (current_array[0] > 0);
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// for (unsigned i = 1; i < k; ++i) {
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// current_array[i] = 2 * current_array[i - 1];
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// Assert (current_array[i-1] < current_array[i]);
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// }
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//
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// We want to check whether the assertion in the body of the for loop holds
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// throughout the loop.
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// Setting up the problem parameters
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int k = 4; // number of unrollings (should be a power of 2)
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int index_size = log2(k); // size of the index
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// Types
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Type elementType = em.mkBitVectorType(32);
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Type indexType = em.mkBitVectorType(index_size);
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Type arrayType = em.mkArrayType(indexType, elementType);
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// Variables
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Expr current_array = em.mkVar("current_array", arrayType);
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// Making a bit-vector constant
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Expr zero = em.mkConst(new BitVector(index_size, 0));
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// Asserting that current_array[0] > 0
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Expr current_array0 = em.mkExpr(Kind.SELECT, current_array, zero);
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Expr current_array0_gt_0 = em.mkExpr(Kind.BITVECTOR_SGT, current_array0, em.mkConst(new BitVector(32, 0)));
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smt.assertFormula(current_array0_gt_0);
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// Building the assertions in the loop unrolling
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Expr index = em.mkConst(new BitVector(index_size, 0));
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Expr old_current = em.mkExpr(Kind.SELECT, current_array, index);
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Expr two = em.mkConst(new BitVector(32, 2));
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vectorExpr assertions = new vectorExpr(em);
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for (int i = 1; i < k; ++i) {
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index = em.mkConst(new BitVector(index_size, new edu.stanford.CVC4.Integer(i)));
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Expr new_current = em.mkExpr(Kind.BITVECTOR_MULT, two, old_current);
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// current[i] = 2 * current[i-1]
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current_array = em.mkExpr(Kind.STORE, current_array, index, new_current);
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// current[i-1] < current [i]
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Expr current_slt_new_current = em.mkExpr(Kind.BITVECTOR_SLT, old_current, new_current);
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assertions.add(current_slt_new_current);
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old_current = em.mkExpr(Kind.SELECT, current_array, index);
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}
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Expr query = em.mkExpr(Kind.NOT, em.mkExpr(Kind.AND, assertions));
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System.out.println("Asserting " + query + " to CVC4 ");
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smt.assertFormula(query);
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System.out.println("Expect sat. ");
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System.out.println("CVC4: " + smt.checkSat(em.mkConst(true)));
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// Getting the model
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System.out.println("The satisfying model is: ");
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System.out.println(" current_array = " + smt.getValue(current_array));
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System.out.println(" current_array[0] = " + smt.getValue(current_array0));
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}
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}
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