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Bounded Sequential Equivalence Checking with Range-Equivalent Circuit, Node Merging , and NAR. Speaker : Chih-Chung Wang Adviser: Chun-Yao Wang. Outline. Problem Formulation Introduction BSEC Node merging NAR Range-equivalent circuit Simple Flowchart and Discussion
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Bounded Sequential Equivalence Checking with Range-Equivalent Circuit, Node Merging, and NAR Speaker: Chih-Chung Wang Adviser: Chun-Yao Wang
Outline • Problem Formulation • Introduction • BSEC • Node merging • NAR • Range-equivalent circuit • Simple Flowchart and Discussion • Problems and Solutions • Future Work
Problem Formulation • Given: • Two boundedsequentialcircuits • A bound timeframe k where it will take much time while using node merging and NAR optimizing BSEC, and the timeframe k-1 has been checked equivalent • Goal: • Bounded sequential equivalence checking (BSEC) at timeframe koptimized by range-equivalent circuit replacement, node merging, and NAR without spending so much time
Bounded Sequential Equivalence Checking (BSEC) • Bounded: timeframe k • Typical BSEC • Miter construction • Unroll • Sequential → Combinational
Speeding Up • Circuit optimization • Node merging • Node addition and removal (NAR)
Speeding Up • Range-equivalent circuit • Range • Range-equivalent • Circuit of timeframe 0 to k-1 replacement
Discussion • Range-equivalent circuit creating function would have runtime error if the input of the circuit whose timeframe is from 0 to k-1 is too big • Segmentation fault • Also taking too much time to run • Using a smaller timeframe n to create range-equivalent circuit • Replacing the circuit 0 to n, and then connecting to the next timeframe n+1 • Repeatedly running until n is equal to k
Resyn2 Original Optimized Construct miter pMiter Resyn2 Optimize NAR pMiterOpt timeframe: 1 Resyn2 Unroll k times pFrame Resyn2 Optimize NAR pFrameOpt timeframe: k Resyn2 SAT solver
Resyn2 Original Optimized Construct miter pMiter Resyn2 NAR Optimize pMiterOpt timeframe: 1 Resyn2 k-1 times Unroll pFramePre Range-equivalent circuit replacement pRange timeframe: k-1 Combine “0tok-1”and “1” pFrame Resyn2 Optimize NAR pFrameOpt timeframe: k Resyn2 SAT solver
Resyn2 Original Optimized Construct miter pMiter Resyn2 NAR Optimize pMiterOpt timeframe: 1 Resyn2 n times, n < k Unroll pFramePre Range-equivalent circuit replacement pRange timeframe: n Combine “0ton”and “1” no n = k ? yes pFrame Optimize NAR Resyn2 pFrameOpt timeframe: k Resyn2 SAT solver
Conclusion • Smaller input circuits for the range-equivalent circuits producing function • Decreasing the runtime error cases • Much more faster • Functions should be modified
Range-equivalent circuits only created by combinational circuits
Problem • Abc’saddframe cannot run because it only accepts sequential circuits as input • While optimizing by range-equivalent circuit, the number of PIs usually decreases
Problem (Cont.) • When repeatedly creating range-equivalent circuits and combining with a new timeframe, the circuits should always be combinational • Modifying the functions of replacing circuit with range-equivalent one and other relating functions
Future Work • Rewriting the functions for combinational circuits • Range-equivalent circuit replacement • Adding a timeframe • Debugging • Experiment result