stiff_convergence:
 n  h  e
   20        0.0500     4461.7461
   40        0.0250        0.5384
   80        0.0125        0.2510
  160        0.0063        0.1551
  320        0.0031        0.1038
  640        0.0016        0.0716
 n  hold/h  eold/e
   40        2.0000     8286.5805
   80        2.0000        2.1453
  160        2.0000        1.6185
  320        2.0000        1.4940
  640        2.0000        1.4499
 n  log10(h)  log10(e)
   20       -1.3010        3.6495
   40       -1.6021       -0.2689
   80       -1.9031       -0.6004
  160       -2.2041       -0.8095
  320       -2.5051       -0.9838
  640       -2.8062       -1.1451