https://pdfs.semanticscholar.org/bbd8/1fa7eb9acaef4115c92c4a40eb4040ad036c.pdf suggests between 0.125 and 0.5 for 2-opt. (higher values = more aggressive)
rat783 optimal = 8806.
// 0.0001: best = 9278.5988 (247180) (60.03s) (penalties = 1641 max_penalty = 842)
// 0.001: best = 8921.7626 (259567) (60.28s) (penalties = 4784 max_penalty = 224)
// 0.01: best = 8855.4163 (204174) (57.67s) (penalties = 14106 max_penalty = 54)
// 0.025: best = 8846.6683 (191518) (57.26s) (penalties = 22467 max_penalty = 32)
// 0.03: best = 8852.2957 (223703) (67.69s) (penalties = 27302 max_penalty = 31)
// 0.04: best = 8847.0568 (206710) (64.62s) (penalties = 30691 max_penalty = 26)
// 0.05: best = 8845.8809 (175955) (55.61s) (penalties = 31312 max_penalty = 21)
// 0.075: best = 8849.9977 (291332) (93.81s) (penalties = 53570 max_penalty = 20
// 0.1: best = 8851.3869 (164248) (53.79s) (penalties = 44185 max_penalty = 13)
// 0.2: best = 8879.8965 (203609) (68.47s) (penalties = 73010 max_penalty = 10)
// 0.3: best = 8892.9067 (151628) (54.70s) (penalties = 75256 max_penalty = 7)
// 1: best = 9154.7613 (109239) (53.25s) (penalties = 98417 max_penalty = 3)
// without triangle
// best = 8844.1745 (194537) (126.22s) (penalties = 10881 max_penalty = 73)
// with triangle
// best = 8844.3483 (455303) (50.73s) (penalties = 17500 max_penalty = 101)
// best = 8844.3264 (1176885) (136.47s) (penalties = 30239 max_penalty = 149)
// best = 8843.9242 (1455928) (170.52s) (penalties = 34298 max_penalty = 169)
// best = 8843.0274 (1583371) (186.37s) (penalties = 36073 max_penalty = 171)
// best = 8843.0068 (2970446) (364.77s) (penalties = 52361 max_penalty = 225)
// best = 8842.9950 (2970474) (364.77s) (penalties = 52361 max_penalty = 225)
// best = 8842.9950 (1127653) (118.21s) (penalties = 19953 max_penalty = 220) 0.025
// best = 8842.9950 (2970474) (360.63s) (penalties = 52361 max_penalty = 225) 0.05
// best = 8842.9950 (1216367) (148.81s) (penalties = 39262 max_penalty = 119) 0.075
// best = 8842.9950 (953709) (109.89s) (penalties = 39960 max_penalty = 92) 0.1
// best = 8842.9950 (1797569) (231.09s) (penalties = 72804 max_penalty = 100) 0.15
// with triangle + deltaP >= 0
// best = 8844.1745 (194537) (127.37s) (penalties = 10881 max_penalty = 73)
// same as without triangle: cur_penalty will always be >= 1 during GLS (don't look bits set to 1)
// edge penalties..
// best = 8844.0546 (853271) (532.46s) (penalties = 25045 max_penalty = 132)
// best = 8843.7396 (1648109) (1022.95s) (penalties = 37031 max_penalty = 172)
// best = 8843.0392 (1648110) (1022.95s) (penalties = 37031 max_penalty = 172)
// best = 8843.0274 (2045430) (1270.90s) (penalties = 42116 max_penalty = 192)
// best = 8842.9950 (2085605) (1295.77s) (penalties = 42660 max_penalty = 192)
// lru+mmf (not worth it..)
// best = 8847.2004 (175895) (179.35s) (penalties = 31311 max_penalty = 21)
// just mmf
// best = 8845.8809 (175955) (84.06s) (penalties = 31312 max_penalty = 21)
// best = 8845.8809 (175955) (183.47s) (penalties = 31312 max_penalty = 21)