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CUDD Overview

CUDD Overview. DoRon Motter July 31, 2001. CUDD. CU Decision Diagram Package Written by Fabio Somenzi at Univ. Colorado Able to create/manipulate BDDs, ZDDs, ADDs. Data Structures. Nodes (DdNode *) Reference Count, T-Edge, E-Edge, Variable Index, (value) Manager (DdManager *)

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CUDD Overview

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  1. CUDD Overview DoRon Motter July 31, 2001

  2. CUDD • CU Decision Diagram Package • Written by Fabio Somenzi at Univ. Colorado • Able to create/manipulate BDDs, ZDDs, ADDs

  3. Data Structures • Nodes (DdNode *) • Reference Count, T-Edge, E-Edge, Variable Index, (value) • Manager (DdManager *) • Encapsulates initialization and uniqueness of a DD • Cache • Memoizes results of recursive computation

  4. Uniqueness of Nodes • Nodes are requested (only) via Unique Table • Hashes T-Edge, E-Edge, index • DdNode * cuddUniqueInter( DdManager * DD, int index, DdNode * T, DdNode * E ) • If a node already exists, return that node. • Otherwise create new node. • Nodes only shared within the same manager

  5. Memory Management • Each node has a reference count • When a BDD is no longer needed, it is recursively dereferenced • N->ref--; if(N->ref == 0) { free(N); Cudd_RecursiveDeref(DD, cuddT(N)); Cudd_RecursiveDeref(DD, cuddE(N)); }

  6. Creating BDDs • BDD Variables can be created by DdNode * Cudd_bddIthVar( DdManager * dd, int i ) • Retrieves the BDD variable with index i if it already exists, or creates a new BDD variable.

  7. Manipulating BDDs • DdNode * Cudd_bddIte( DdManager * dd, DdNode * f, DdNode * g, DdNode * h ) • Cudd_bddAnd, Cudd_bddOr, Cudd_bddXor, Cudd_bddNand, Cudd_bddXnor, …

  8. f = x0'x1'x2'x3'. • f = Cudd_ReadOne(manager); Cudd_Ref(f); for (i = 3; i >= 0; i--) { var = Cudd_bddIthVar(manager,i); tmp = Cudd_bddAnd(manager, Cudd_Not(var),f); Cudd_Ref(tmp); Cudd_RecursiveDeref(manager,f); f = tmp; }

  9. Reordering Variables • Variable ordering in DD’s influences size • CUDD provides methods for reordering variables • void Cudd_AutodynEnable( DdManager * unique, Cudd_ReorderingType method ) • Sifting, Random, Converging Sift, Symmetric Sift, Random Pivot, None…

  10. Debugging CUDD • Most important topic! • CUDD can print the DD to stdout. • int Cudd_PrintDebug( DdManager * dd, DdNode * f, int n, int pr ) • CUDD can also redirect stdout, etc. • CUDD can dump DD’s to .dot, .blif • Often DD’s are too large to be processed by GraphViz • Often DD’s are too large to be dumped to stdout!

  11. CUDD .dot output

  12. Questions?

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