2010 run = 2000 steps (a 100,000 digits)
2012 run = 4770 steps (a 100,000 digits)
2013 run = 11000 steps (a 100,000 digits)
2017 run = 11000 steps (a 100,000 digits)

2017 matches to 2010 until step 1016
2017 matches to 2012 until step 4770
2017 matches to 2013 until yet

2010-run slowdown factor : 197.5 sec / step
                           0.001975 sec / digit

2012-run slowdown factor : 8.2166666666667 sec / step
                           8.2166666666667E-5 sec / digit

2013-run slowdown factor : 3.1125 sec / step
                           3.1125E-5 sec / digit

2017-run slowdown factor : 1.227621483376 sec / step
                           1.227621483376E-5 sec / digit