77 lines
2.1 KiB
C++
77 lines
2.1 KiB
C++
/* This program creates a transition relation for a finite state machine.
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* This transition relation is then used to find the reachable statespace
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* of the state machine. The state machine has 8 states with state 0 being
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* the initial state. The transitions form a ring:
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*
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* 0 -> 1 -> 2 -> 3 -> 4 -> 5 -> -> 7 -> 0
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*/
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#include "fdd.h"
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/* Use the transition relation "transRel" to iterate through the statespace
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*/
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void findStateSpace(bdd transRel)
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{
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/* Create a new pair for renaming the next-state variables to
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* current-state variables */
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bddPair *p = bdd_newpair();
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fdd_setpair(p,1,0);
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/* Get a BDD that represents all the current-state variables */
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bdd currentStateVar = fdd_ithset(0);
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/* Start with the initial state */
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bdd reachedStates = fdd_ithvar(0,0);
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bdd tmp = bddfalse;
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/* Repeat until no new states are found */
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do
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{
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tmp = reachedStates;
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/* Calculate: Newset = (exists V_cur. transRel & Reached)[cur/next] */
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bdd newset;
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newset = reachedStates & transRel;
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newset = bdd_exist(newset, currentStateVar);
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newset = bdd_replace(newset, p);
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cout << "Front: " << (newset - reachedStates) << endl;
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/* Add the new states to the found states */
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reachedStates = reachedStates | newset;
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}
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while (tmp != reachedStates);
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}
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main()
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{
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/* Initialize BuDDy and declare two interleaved FDD variable blocks
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* with the domain [0..7] */
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int domain[2] = {8,8};
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bdd_init(100,100);
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fdd_extdomain(domain, 2);
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/* Initialize the transition relation with no transitions */
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bdd T = bddfalse;
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/* Add all the transitions (from state 'i' to state 'i+1') */
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for (int i=0 ; i<8 ; i++)
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{
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/* Set the current state to be state 'i' */
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bdd current = fdd_ithvar(0,i);
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/* Set the next state to be state 'i+1' */
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bdd next = fdd_ithvar(1, (i+1) % 8);
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/* Add the transition */
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T = T | (current & next);
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}
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cout << fddset << "Transition relation: " << T << endl << endl;
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/* Calculate the reachable statespace */
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findStateSpace(T);
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}
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