BTW sandpile log (7 million grains)

btw.log

#4096 iterations; C = 4; radius = 300; elapsed = 5.421 s
#8192 iterations; C = 4; radius = 395; elapsed = 18.826 s
#12288 iterations; C = 4; radius = 462; elapsed = 39.843 s
#16384 iterations; C = 4; radius = 515; elapsed = 68.195 s
#20480 iterations; C = 4; radius = 560; elapsed = 100.019 s
#24576 iterations; C = 4; radius = 599; elapsed = 136.519 s
#28672 iterations; C = 4; radius = 634; elapsed = 175.452 s
#32768 iterations; C = 4; radius = 665; elapsed = 218.211 s
#36864 iterations; C = 4; radius = 694; elapsed = 265.05 s
#40960 iterations; C = 4; radius = 720; elapsed = 315.367 s
#45056 iterations; C = 4; radius = 744; elapsed = 369.16 s
#49152 iterations; C = 4; radius = 767; elapsed = 427.044 s
#53248 iterations; C = 4; radius = 788; elapsed = 489.033 s
#57344 iterations; C = 4; radius = 808; elapsed = 554.42 s
#61440 iterations; C = 4; radius = 827; elapsed = 624.258 s
#65536 iterations; C = 4; radius = 845; elapsed = 693.73 s
#69632 iterations; C = 4; radius = 862; elapsed = 765.775 s
#73728 iterations; C = 4; radius = 878; elapsed = 842.715 s
#77824 iterations; C = 4; radius = 894; elapsed = 920.596 s
#81920 iterations; C = 4; radius = 909; elapsed = 1002.575 s
#86016 iterations; C = 4; radius = 923; elapsed = 1084.457 s
#90112 iterations; C = 4; radius = 937; elapsed = 1170.692 s
#94208 iterations; C = 4; radius = 950; elapsed = 1256.755 s
#98304 iterations; C = 4; radius = 963; elapsed = 1344.675 s
#102400 iterations; C = 4; radius = 975; elapsed = 1434.81 s
#106496 iterations; C = 4; radius = 987; elapsed = 1527.281 s
#110592 iterations; C = 4; radius = 998; elapsed = 1623.011 s
#114688 iterations; C = 4; radius = 1009; elapsed = 1731.804 s
#118784 iterations; C = 4; radius = 1020; elapsed = 1843.279 s
#122880 iterations; C = 4; radius = 1031; elapsed = 1956.218 s
#126976 iterations; C = 4; radius = 1041; elapsed = 2071.208 s
#131072 iterations; C = 4; radius = 1050; elapsed = 2188.392 s
#135168 iterations; C = 4; radius = 1060; elapsed = 2307.568 s
#139264 iterations; C = 4; radius = 1069; elapsed = 2421.368 s
#143360 iterations; C = 4; radius = 1077; elapsed = 2526.163 s
#147456 iterations; C = 4; radius = 1086; elapsed = 2632.155 s
#151552 iterations; C = 4; radius = 1094; elapsed = 2742.353 s
#155648 iterations; C = 4; radius = 1102; elapsed = 2855.235 s
#159744 iterations; C = 4; radius = 1110; elapsed = 2969.843 s
#163840 iterations; C = 4; radius = 1117; elapsed = 3087.694 s
#167936 iterations; C = 4; radius = 1125; elapsed = 3205.019 s
#172032 iterations; C = 4; radius = 1132; elapsed = 3323.816 s
#176128 iterations; C = 4; radius = 1139; elapsed = 3443.725 s
#180224 iterations; C = 4; radius = 1145; elapsed = 3563.276 s
#184320 iterations; C = 4; radius = 1152; elapsed = 3683.172 s
#188416 iterations; C = 4; radius = 1158; elapsed = 3805.464 s
#192512 iterations; C = 4; radius = 1164; elapsed = 3926.764 s
#196608 iterations; C = 4; radius = 1171; elapsed = 4047.124 s
#200704 iterations; C = 4; radius = 1177; elapsed = 4168.135 s
#204800 iterations; C = 4; radius = 1182; elapsed = 4290.403 s
#208896 iterations; C = 4; radius = 1188; elapsed = 4416.319 s
#212992 iterations; C = 4; radius = 1193; elapsed = 4548.893 s
#217088 iterations; C = 4; radius = 1199; elapsed = 4681.377 s
#221184 iterations; C = 4; radius = 1204; elapsed = 4815.109 s
#225280 iterations; C = 4; radius = 1209; elapsed = 4947.355 s
#229376 iterations; C = 4; radius = 1214; elapsed = 5073.905 s
#233472 iterations; C = 4; radius = 1219; elapsed = 5199.26 s
#237568 iterations; C = 4; radius = 1224; elapsed = 5333.578 s
#241664 iterations; C = 4; radius = 1229; elapsed = 5466.444 s
#245760 iterations; C = 4; radius = 1233; elapsed = 5593.879 s
#249856 iterations; C = 4; radius = 1237; elapsed = 5721.282 s
#253952 iterations; C = 4; radius = 1242; elapsed = 5846.704 s
#258048 iterations; C = 4; radius = 1246; elapsed = 5973.87 s
#262144 iterations; C = 4; radius = 1250; elapsed = 6109.115 s
#266240 iterations; C = 4; radius = 1254; elapsed = 6246.21 s
#270336 iterations; C = 4; radius = 1258; elapsed = 6375.675 s
#274432 iterations; C = 4; radius = 1262; elapsed = 6501.913 s
#278528 iterations; C = 4; radius = 1266; elapsed = 6628.283 s
#282624 iterations; C = 4; radius = 1270; elapsed = 6754.914 s
#286720 iterations; C = 4; radius = 1273; elapsed = 6881.747 s
#290816 iterations; C = 4; radius = 1277; elapsed = 7008.437 s
#294912 iterations; C = 4; radius = 1281; elapsed = 7136.871 s
#299008 iterations; C = 4; radius = 1284; elapsed = 7274.984 s
#303104 iterations; C = 4; radius = 1287; elapsed = 7413.647 s
#307200 iterations; C = 4; radius = 1291; elapsed = 7550.741 s
#311296 iterations; C = 4; radius = 1294; elapsed = 7688.803 s
#315392 iterations; C = 4; radius = 1297; elapsed = 7816.849 s
#319488 iterations; C = 4; radius = 1300; elapsed = 7955.052 s
#323584 iterations; C = 4; radius = 1303; elapsed = 8084.946 s
#327680 iterations; C = 4; radius = 1306; elapsed = 8218.563 s
#331776 iterations; C = 4; radius = 1309; elapsed = 8360.843 s
#335872 iterations; C = 4; radius = 1312; elapsed = 8498.292 s
#339968 iterations; C = 4; radius = 1314; elapsed = 8643.159 s
#344064 iterations; C = 4; radius = 1317; elapsed = 8779.622 s
#348160 iterations; C = 4; radius = 1319; elapsed = 8907.952 s
#352256 iterations; C = 4; radius = 1322; elapsed = 9049.428 s
#356352 iterations; C = 4; radius = 1325; elapsed = 9194.492 s
#360448 iterations; C = 4; radius = 1327; elapsed = 9327.522 s
#364544 iterations; C = 4; radius = 1329; elapsed = 9451.234 s
#368640 iterations; C = 4; radius = 1332; elapsed = 9577.61 s
#372736 iterations; C = 4; radius = 1334; elapsed = 9697.967 s
#376832 iterations; C = 4; radius = 1336; elapsed = 9818.375 s
#380928 iterations; C = 4; radius = 1339; elapsed = 9937.805 s
#385024 iterations; C = 4; radius = 1341; elapsed = 10057.401 s
#389120 iterations; C = 4; radius = 1343; elapsed = 10176.198 s
#393216 iterations; C = 4; radius = 1345; elapsed = 10294.824 s
#397312 iterations; C = 4; radius = 1347; elapsed = 10413.194 s
#401408 iterations; C = 4; radius = 1349; elapsed = 10530.546 s
#405504 iterations; C = 4; radius = 1351; elapsed = 10648.094 s
#409600 iterations; C = 4; radius = 1353; elapsed = 10784.35 s
#413696 iterations; C = 4; radius = 1355; elapsed = 10911.922 s
#417792 iterations; C = 4; radius = 1357; elapsed = 11045.315 s
#421888 iterations; C = 4; radius = 1358; elapsed = 11174.963 s
#425984 iterations; C = 4; radius = 1360; elapsed = 11304.983 s
#430080 iterations; C = 4; radius = 1362; elapsed = 11435.71 s
#434176 iterations; C = 4; radius = 1363; elapsed = 11567.267 s
#438272 iterations; C = 4; radius = 1365; elapsed = 11693.063 s
#442368 iterations; C = 4; radius = 1367; elapsed = 11817.472 s
#446464 iterations; C = 4; radius = 1368; elapsed = 11941.269 s
#450560 iterations; C = 4; radius = 1370; elapsed = 12054.723 s
#454656 iterations; C = 4; radius = 1371; elapsed = 12166.457 s
#458752 iterations; C = 4; radius = 1373; elapsed = 12279.724 s
#462848 iterations; C = 4; radius = 1374; elapsed = 12390.312 s
#466944 iterations; C = 4; radius = 1375; elapsed = 12497.901 s
#471040 iterations; C = 4; radius = 1377; elapsed = 12604.977 s
#475136 iterations; C = 4; radius = 1378; elapsed = 12711.304 s
#479232 iterations; C = 4; radius = 1379; elapsed = 12816.468 s
#483328 iterations; C = 4; radius = 1381; elapsed = 12920.832 s
#487424 iterations; C = 4; radius = 1382; elapsed = 13023.537 s
#491520 iterations; C = 4; radius = 1383; elapsed = 13124.632 s
#495616 iterations; C = 4; radius = 1384; elapsed = 13224.647 s
#499712 iterations; C = 4; radius = 1385; elapsed = 13324.251 s
#503808 iterations; C = 4; radius = 1386; elapsed = 13422.612 s
#507904 iterations; C = 4; radius = 1387; elapsed = 13518.831 s
#512000 iterations; C = 4; radius = 1388; elapsed = 13615.476 s
#516096 iterations; C = 4; radius = 1388; elapsed = 13713.304 s
#520192 iterations; C = 4; radius = 1389; elapsed = 13808.782 s
#524288 iterations; C = 4; radius = 1390; elapsed = 13904.384 s
#528384 iterations; C = 4; radius = 1391; elapsed = 13996.918 s
#532480 iterations; C = 4; radius = 1391; elapsed = 14092.224 s
#536576 iterations; C = 4; radius = 1392; elapsed = 14186.9 s
#540672 iterations; C = 4; radius = 1392; elapsed = 14275.245 s
#544768 iterations; C = 4; radius = 1393; elapsed = 14363.589 s
#548864 iterations; C = 4; radius = 1393; elapsed = 14455.795 s
#552960 iterations; C = 4; radius = 1394; elapsed = 14545.828 s
#557056 iterations; C = 4; radius = 1394; elapsed = 14635.695 s
#561152 iterations; C = 4; radius = 1395; elapsed = 14718.498 s
#565248 iterations; C = 4; radius = 1395; elapsed = 14800.051 s
#569344 iterations; C = 4; radius = 1396; elapsed = 14880.035 s
#573440 iterations; C = 4; radius = 1396; elapsed = 14959.196 s
#577536 iterations; C = 4; radius = 1396; elapsed = 15039.058 s
#581632 iterations; C = 4; radius = 1396; elapsed = 15118.813 s
#585728 iterations; C = 4; radius = 1397; elapsed = 15207.196 s
#589824 iterations; C = 4; radius = 1397; elapsed = 15295.895 s
#593920 iterations; C = 4; radius = 1397; elapsed = 15385.611 s
#598016 iterations; C = 4; radius = 1397; elapsed = 15459.363 s
#602112 iterations; C = 4; radius = 1397; elapsed = 15533.075 s
#606208 iterations; C = 4; radius = 1397; elapsed = 15606.459 s
#610304 iterations; C = 4; radius = 1397; elapsed = 15680.144 s
#614400 iterations; C = 4; radius = 1397; elapsed = 15750.05 s
#618496 iterations; C = 4; radius = 1397; elapsed = 15821.426 s
#622592 iterations; C = 4; radius = 1397; elapsed = 15891.791 s
#626688 iterations; C = 4; radius = 1397; elapsed = 15963.21 s
#630665 iterations; C = 4; radius = 1397; elapsed = 16031.351 s