More evidence that SRHD-SGI produces hard SAT instances

In this paper we test whether the properties of the SAT encoded SRHD-SGI instances are independent of the encoding scheme. We selected for our experiments several SAT solvers that won medals at the last SAT competition and a solver that performed very well on the direct encoded SRHD-SGI instances used in the competition. We tested four encoding of SGI to SAT based on converting the original SGI instance into a PBC instance and then from PBC to SAT. We found that the most important properties of SAT encoded SRHD-SGI are preserved under all encodings and, therefore, we concluded that these properties are independent of the encoding scheme¹.