Comments on "A method of fault simulation based on stem regions

For the original article see ibid., vol.9, no.2, p.212-20 (1990). The commenters show a counterexample for the region extraction algorithm given in the above-mentioned work by F. Maamari and J. Rajski. A four-step region extraction algorithm was given to extract the exit lines of each stem. In steps 1 and 2, primary reconvergent gates (PRGs) and secondary reconvergent gates (SRGs) of the stem are identified. In steps 3 and 4, closing reconvergent gates (CRGs) and exit lines are computed. In step 2, the algorithm does not identify some SRGs which could be exit lines of the stem. As a result, the fault simulation may be incorrect for some faults. The commenters show this case using an example circuit.<>