Abstract: The amount of analysis performed in determining the validity of a property of a digital circuit is measured concurrent with performance of the analysis, and provided as an output when a true/false answer cannot be provided e.g. when stopped due to resource constraints. In some embodiments, a measure of value N indicates that a given property that is being checked will not be violated within a distance N from an initial state from which the analysis started. Therefore, in such embodiments, a measure of value N indicates that the analysis has implicitly or explicitly covered every possible excursion of length N from the initial state, and formally proved that no counter-example is possible within this length N.

Abstract: A programmed computer searches for functional defects in a description of a circuit undergoing functional verification in the following manner. The programmed computer simulates the functional behavior of the circuit in response to a test vector, automatically restores the state of the simulation without causing the simulation to pass through a reset state, and then simulates the functional behavior of the circuit in response to another test vector. A predetermined rule can be used to identify test vectors to be simulated, and the predetermined rule can depend upon a measure of functional verification, including the number of times during simulation when a first state transition is performed by a first-controller at the same time as a second state transition is performed by a second controller. During simulation of the test vectors, manually generated tests or automatically generated checkers can monitor portions of the circuit for defective behavior.

Abstract: The amount of analysis performed in determining the validity of a property of a digital circuit is measured concurrent with performance of the analysis, and provided as an output when a true/false answer cannot be provided e.g. when stopped due to resource constraints. In some embodiments, a measure of value N indicates that a given property that is being checked will not be violated within a distance N from an initial state from which the analysis started. Therefore, in such embodiments, a measure of value N indicates that the analysis has implicitly or explicitly covered every possible excursion of length N from the initial state, and formally proved that no counter-example is possible within this length N.