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12444c7e8b
* Implement phase saving * Implement signed comparison on BDD vectors * Add fdd::non_zero * Simplify construction of fdds over disjoint variables * Minor changes to adding constraint
76 lines
2.4 KiB
C++
76 lines
2.4 KiB
C++
/*++
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Copyright (c) 2021 Microsoft Corporation
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Module Name:
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dd_fdd
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Abstract:
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Finite domain abstraction for using BDDs as sets of integers, inspired by BuDDy's fdd module.
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Author:
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Nikolaj Bjorner (nbjorner) 2021-04-20
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Jakob Rath 2021-04-20
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--*/
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#pragma once
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#include "math/dd/dd_bdd.h"
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#include "util/vector.h"
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#include "util/rational.h"
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namespace dd {
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enum class find_t { empty, singleton, multiple };
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std::ostream& operator<<(std::ostream& out, find_t x);
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/**
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* Finite domain abstraction over BDDs.
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*/
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class fdd {
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unsigned_vector m_pos2var; // pos -> BDD var
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unsigned_vector m_var2pos; // var -> pos (pos = place number in the bit representation, 0 is LSB's place)
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bdd_manager* m;
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bddv m_var;
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static unsigned_vector seq(unsigned count, unsigned start = 0, unsigned step = 1) {
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unsigned_vector result;
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unsigned k = start;
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for (unsigned i = 0; i < count; ++i, k += step)
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result.push_back(k);
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return result;
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}
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unsigned var2pos(unsigned var) const;
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public:
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/** Initialize FDD using BDD variables from 0 to num_bits-1. */
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fdd(bdd_manager& manager, unsigned num_bits, unsigned start = 0, unsigned step = 1) : fdd(manager, seq(num_bits, start, step)) { }
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fdd(bdd_manager& manager, unsigned_vector const& vars) : fdd(manager, unsigned_vector(vars)) { }
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fdd(bdd_manager& manager, unsigned_vector&& vars);
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unsigned num_bits() const { return m_pos2var.size(); }
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unsigned_vector const& bdd_vars() const { return m_pos2var; }
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bddv const& var() const { return m_var; }
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/** Equivalent to var() != 0 */
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bdd non_zero() const;
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/** Checks whether the integer val is contained in the BDD when viewed as set of integers.
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* Precondition: the bdd only contains variables managed by this fdd.
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*/
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bool contains(bdd b, rational const& val) const;
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/** Returns an integer contained in the BDD, if any, and whether the BDD is a singleton.
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* Precondition: the bdd only contains variables managed by this fdd.
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*/
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find_t find(bdd b, rational& out_val) const;
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/** Like find, but returns hint if it is contained in the BDD. */
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find_t find_hint(bdd b, rational const& hint, rational& out_val) const;
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};
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}
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