Error detection in arrays via dependency graphs

This paper describes a methodology based on dependency graphs for doing concurrent run-time error detection in systolic arrays and wavefront processors. It combines the projection method of deriving systolic arrays from dependency graphs with the idea of input-triggered testing. We call the method ITRED, for Input-driven Time-Redundancy Error Detection. Tests are triggered by inserting special symbols in the input, and so the approach gives the user flexibility in trading off throughput for error coverage. Correctness of timing is proved at the dependency graph level. The method requires no extra PEs and little extra hardware. We propose several variations of the general approach and derive corresponding constraints on the modified dependency graphs that guarantee correctness. One variation performs run-time error correction using majority voting. Examples are given, including a dynamic programming algorithm, convolution, and matrix multiplication.