Merge branch 'master' of https://github.com/Z3Prover/z3

src/ast/CMakeLists.txt

@@ -23,6 +23,7 @@ z3_add_component(ast
     expr_map.cpp
     expr_stat.cpp
     expr_substitution.cpp
+    factor_equivs.cpp
     for_each_ast.cpp
     for_each_expr.cpp
     format.cpp

src/ast/factor_equivs.cpp

@@ -0,0 +1,109 @@
+/*++
+Copyright (c) 2017 Arie Gurfinkel
+
+Module Name:
+
+    factor_equivs.cpp
+
+Abstract:
+  Factor equivalence classes out of an expression.
+
+  "Equivalence class structure" for objs. Uses a union_find structure internally.
+  Operations are :
+  -Declare a new equivalence class with a single element
+  -Merge two equivalence classes
+  -Retrieve whether two elements are in the same equivalence class
+  -Iterate on all the elements of the equivalence class of a given element
+  -Iterate on all equivalence classes (and then within them)
+
+Author:
+
+    Julien Braine
+    Arie Gurfinkel
+
+Revision History:
+
+*/
+
+#include "ast/factor_equivs.h"
+#include "ast/arith_decl_plugin.h"
+
+/**
+   Factors input vector v into equivalence classes and the rest
+ */
+void factor_eqs(expr_ref_vector &v, expr_equiv_class &equiv) {
+    ast_manager &m = v.get_manager();
+    arith_util arith(m);
+    expr *e1 = 0, *e2 = 0;
+
+    flatten_and(v);
+    unsigned j = 0;
+    for (unsigned i = 0; i < v.size(); ++i) {
+        if (m.is_eq(v.get(i), e1, e2)) {
+            if (arith.is_zero(e1)) {
+                std::swap(e1, e2);
+            }
+
+            // y + -1*x == 0
+            expr* a0 = 0, *a1 = 0, *x = 0;
+            if (arith.is_zero(e2) && arith.is_add(e1, a0, a1)) {
+                if (arith.is_times_minus_one(a1, x)) {
+                    e1 = a0;
+                    e2 = x;
+                }
+                else if (arith.is_times_minus_one(a0, x)) {
+                    e1 = a1;
+                    e2 = x;
+                }
+            }
+            equiv.merge(e1, e2);
+        }
+        else {
+            if (j < i) { 
+                v[j] = v.get(i); 
+            }
+            j++;
+        }
+    }
+    v.shrink(j);
+}
+
+/**
+ * converts equivalence classes to equalities
+ */
+void equiv_to_expr(expr_equiv_class &equiv, expr_ref_vector &out) {
+    ast_manager &m = out.get_manager();
+    for (auto eq_class : equiv) {
+        expr *rep = nullptr;
+        for (expr *elem : eq_class) {
+            if (!m.is_value(elem)) {
+                rep = elem;
+                break;
+            }
+        }
+        SASSERT(rep);
+        for (expr *elem : eq_class) {
+            if (rep != elem) {
+                out.push_back (m.mk_eq (rep, elem));
+            }
+        }
+    }
+}
+
+/**
+ * expands equivalence classes to all derivable equalities
+ */
+bool equiv_to_expr_full(expr_equiv_class &equiv, expr_ref_vector &out) {
+    ast_manager &m = out.get_manager();
+    bool dirty = false;
+    for (auto eq_class : equiv) {
+        for (auto a = eq_class.begin(), end = eq_class.end(); a != end; ++a) {
+            expr_equiv_class::iterator b(a);
+            for (++b; b != end; ++b) {
+                out.push_back(m.mk_eq(*a, *b));
+                dirty = true;
+            }
+        }
+    }
+    return dirty;
+}

src/ast/factor_equivs.h

@@ -0,0 +1,183 @@
+/*++
+Copyright (c) 2017 Arie Gurfinkel
+
+Module Name:
+
+    factor_equivs.h
+
+Abstract:
+  Factor equivalence classes out of an expression.
+
+  "Equivalence class structure" for objs. Uses a union_find structure internally.
+  Operations are :
+  -Declare a new equivalence class with a single element
+  -Merge two equivalence classes
+  -Retrieve whether two elements are in the same equivalence class
+  -Iterate on all the elements of the equivalence class of a given element
+  -Iterate on all equivalence classes (and then within them)
+
+Author:
+
+    Julien Braine
+    Arie Gurfinkel
+
+Revision History:
+
+*/
+
+#ifndef FACTOR_EQUIVS_H_
+#define FACTOR_EQUIVS_H_
+
+#include "util/union_find.h"
+#include "ast/ast_util.h"
+
+///All functions naturally add their parameters to the union_find class
+template<typename OBJ, typename Manager>
+class obj_equiv_class {
+    basic_union_find m_uf;
+    obj_map<OBJ, unsigned> m_to_int;
+    ref_vector<OBJ, Manager> m_to_obj;
+
+    unsigned add_elem_impl(OBJ*o) {
+        unsigned id = m_to_obj.size();
+        m_to_int.insert(o, id);
+        m_to_obj.push_back(o);
+        return id;
+    }
+    unsigned add_if_not_there(OBJ*o) {
+        unsigned id;
+        if(!m_to_int.find(o, id)) {
+            id = add_elem_impl(o);
+        }
+        return id;
+    }
+
+public:
+    class iterator;
+    class equiv_iterator;
+    friend class iterator;
+    friend class equiv_iterator;
+
+    obj_equiv_class(Manager& m) : m_to_obj(m) {}
+
+    void add_elem(OBJ*o) {
+        SASSERT(!m_to_int.find(o));
+        add_elem_impl(o);
+    }
+
+    //Invalidates all iterators
+    void merge(OBJ* a, OBJ* b) {
+        unsigned v1 = add_if_not_there(a);
+        unsigned v2 = add_if_not_there(b);
+        unsigned tmp1 = m_uf.find(v1);
+        unsigned tmp2 = m_uf.find(v2);
+        m_uf.merge(tmp1, tmp2);
+    }
+
+    void reset() {
+        m_uf.reset();
+        m_to_int.reset();
+        m_to_obj.reset();
+    }
+
+    bool are_equiv(OBJ*a, OBJ*b) {
+        unsigned id1 = add_if_not_there(a);
+        unsigned id2 = add_if_not_there(b);
+        return m_uf.find(id1) == m_uf.find(id2);
+    }
+
+    class iterator {
+        friend class obj_equiv_class;
+    private :
+        const obj_equiv_class& m_ouf;
+        unsigned m_curr_id;
+        bool m_first;
+        iterator(const obj_equiv_class& uf, unsigned id, bool f) :
+            m_ouf(uf), m_curr_id(id), m_first(f) {}
+    public :
+        OBJ*operator*() {return m_ouf.m_to_obj[m_curr_id];}
+
+        iterator& operator++() {
+            m_curr_id = m_ouf.m_uf.next(m_curr_id);
+            m_first = false;
+            return *this;
+        }
+        bool operator==(const iterator& o) {
+            SASSERT(&m_ouf == &o.m_ouf);
+            return  m_first == o.m_first && m_curr_id == o.m_curr_id;
+        }
+        bool operator!=(const iterator& o) {return !(*this == o);}
+    };
+
+    iterator begin(OBJ*o) {
+        unsigned id = add_if_not_there(o);
+        return iterator(*this, id, true);
+    }
+    iterator end(OBJ*o) {
+        unsigned id = add_if_not_there(o);
+        return iterator(*this, id, false);
+    }
+
+    class eq_class {
+    private :
+        iterator m_begin;
+        iterator m_end;
+    public :
+        eq_class(const iterator& a, const iterator& b) : m_begin(a), m_end(b) {}
+        iterator begin() {return m_begin;}
+        iterator end() {return m_end;}
+    };
+
+    class equiv_iterator {
+        friend class obj_equiv_class;
+    private :
+        const obj_equiv_class& m_ouf;
+        unsigned m_rootnb;
+        equiv_iterator(const obj_equiv_class& uf, unsigned nb) :
+            m_ouf(uf), m_rootnb(nb) {
+            while(m_rootnb != m_ouf.m_to_obj.size() &&
+                  m_ouf.m_uf.is_root(m_rootnb) != true)
+            { m_rootnb++; }
+        }
+    public :
+        eq_class operator*() {
+            return eq_class(iterator(m_ouf, m_rootnb, true),
+                            iterator(m_ouf, m_rootnb, false));
+        }
+        equiv_iterator& operator++() {
+            do {
+                m_rootnb++;
+            } while(m_rootnb != m_ouf.m_to_obj.size() &&
+                    m_ouf.m_uf.is_root(m_rootnb) != true);
+            return *this;
+        }
+        bool operator==(const equiv_iterator& o) {
+            SASSERT(&m_ouf == &o.m_ouf);
+            return m_rootnb == o.m_rootnb;
+        }
+        bool operator!=(const equiv_iterator& o) {return !(*this == o);}
+    };
+
+    equiv_iterator begin() {return equiv_iterator(*this, 0);}
+    equiv_iterator end() {return equiv_iterator(*this, m_to_obj.size());}
+};
+
+typedef obj_equiv_class<expr, ast_manager> expr_equiv_class;
+
+
+/**
+ *  Factors input vector v into equivalence classes and the rest
+ */
+void factor_eqs(expr_ref_vector &v, expr_equiv_class &equiv);
+/**
+ * converts equivalence classes to equalities
+ */
+void equiv_to_expr(expr_equiv_class &equiv, expr_ref_vector &out);
+
+/**
+ * expands equivalence classes to all derivable equalities
+ */
+bool equiv_to_expr_full(expr_equiv_class &equiv, expr_ref_vector &out);
+
+
+#endif