(116.72, 638.24) (123.26, 638.24) (123.26, 644.23) (116.72, 644.23) /F1 15 <|special_separator|> (150.01, 638.24) (159.83, 638.24) (159.83, 644.23) (150.01, 644.23) /F1 300 <|special_separator|> (183.31, 638.24) (196.39, 638.24) (196.39, 644.23) (183.31, 644.23) /F1 6000 <|special_separator|> (123.60, 629.76) (185.15, 629.76) (185.15, 638.58) (123.60, 638.58) /F1 Solution Length <|special_separator|> (105.76, 644.98) (113.94, 644.98) (113.94, 650.97) (105.76, 650.97) /F1 0.0 <|special_separator|> (105.76, 673.86) (113.94, 673.86) (113.94, 679.85) (105.76, 679.85) /F1 0.5 <|special_separator|> (105.76, 702.73) (113.94, 702.73) (113.94, 708.73) (105.76, 708.73) /F1 1.0 <|special_separator|> (104.89, 651.44) (104.89, 702.60) (096.06, 702.60) (096.06, 651.44) /F1 Success Rate <|special_separator|> (142.75, 710.19) (166.00, 710.19) (166.00, 719.33) (142.75, 719.33) /F1 Rubik <|special_separator|> (199.63, 638.36) (206.16, 638.36) (206.16, 644.33) (199.63, 644.33) /F1 10 <|special_separator|> (232.81, 638.36) (242.60, 638.36) (242.60, 644.33) (232.81, 644.33) /F1 200 <|special_separator|> (265.98, 638.36) (279.04, 638.36) (279.04, 644.33) (265.98, 644.33) /F1 4000 <|special_separator|> (206.44, 629.88) (267.88, 629.88) (267.88, 638.70) (206.44, 638.70) /F1 Solution Length <|special_separator|> (216.13, 710.07) (258.18, 710.07) (258.18, 719.20) (216.13, 719.20) /F1 Lights Out <|special_separator|> (281.48, 638.41) (287.99, 638.41) (287.99, 644.38) (281.48, 644.38) /F1 10 <|special_separator|> (316.35, 638.41) (322.86, 638.41) (322.86, 644.38) (316.35, 644.38) /F1 30 <|special_separator|> (351.23, 638.41) (357.74, 638.41) (357.74, 644.38) (351.23, 644.38) /F1 90 <|special_separator|> (288.83, 629.97) (350.08, 629.97) (350.08, 638.75) (288.83, 638.75) /F1 Solution Length <|special_separator|> (302.36, 710.01) (336.53, 710.01) (336.53, 719.11) (302.36, 719.11) /F1 Sokoban <|special_separator|> (365.60, 638.40) (368.87, 638.40) (368.87, 644.38) (365.60, 644.38) /F1 9 <|special_separator|> (396.94, 638.40) (403.48, 638.40) (403.48, 644.38) (396.94, 644.38) /F1 27 <|special_separator|> (429.92, 638.40) (436.45, 638.40) (436.45, 644.38) (429.92, 644.38) /F1 81 <|special_separator|> (369.33, 629.93) (430.79, 629.93) (430.79, 638.74) (369.33, 638.74) /F1 Solution Length <|special_separator|> (374.58, 710.14) (425.55, 710.14) (425.55, 719.27) (374.58, 719.27) /F1 Digit Jumper <|special_separator|> (442.70, 638.20) (449.25, 638.20) (449.25, 644.20) (442.70, 644.20) /F1 40 <|special_separator|> (474.19, 638.20) (484.01, 638.20) (484.01, 644.20) (474.19, 644.20) /F1 120 <|special_separator|> (507.32, 638.20) (517.14, 638.20) (517.14, 644.20) (507.32, 644.20) /F1 360 <|special_separator|> (448.14, 629.71) (509.77, 629.71) (509.77, 638.54) (448.14, 638.54) /F1 Solution Length <|special_separator|> (459.73, 710.23) (498.18, 710.23) (498.18, 719.38) (459.73, 719.38) /F1 15-Puzzle <|special_separator|> (215.87, 612.72) (304.33, 612.72) (304.33, 622.10) (215.87, 622.10) /F1 CRTR without Search <|special_separator|> (342.98, 612.72) (418.69, 612.72) (418.69, 622.10) (342.98, 622.10) /F1 CRTR with BestFS <|special_separator|> (108.00, 591.62) (145.50, 591.62) (145.50, 600.17) (108.00, 600.17) /F116 Figure 4: <|special_separator|> (149.73, 591.81) (364.62, 591.81) (364.62, 599.87) (149.73, 599.87) /F107 CRTR solves most tasks without requiring any search. <|special_separator|> (369.41, 591.62) (504.17, 591.62) (504.17, 600.17) (369.41, 600.17) /F116 Adding BestFS results in shorter <|special_separator|> (108.00, 580.71) (467.83, 580.71) (467.83, 589.26) (108.00, 589.26) /F116 solutions. We plot the fraction of configurations solved with a solution length of at most <|special_separator|> (470.49, 580.87) (476.18, 580.87) (476.18, 589.58) (470.49, 589.58) /F27 x <|special_separator|> (476.18, 580.71) (504.00, 580.71) (504.00, 589.26) (476.18, 589.26) /F116 , while <|special_separator|> (108.00, 569.80) (503.99, 569.80) (503.99, 578.35) (108.00, 578.35) /F116 limiting the number of nodes created to 6000. Surprisingly, on the Rubik's cube CRTR achieves a <|special_separator|> (108.00, 558.89) (183.73, 558.89) (183.73, 567.44) (108.00, 567.44) /F116 higher success rate <|special_separator|> (186.23, 559.03) (216.33, 559.03) (216.33, 567.62) (186.23, 567.62) /F134 without <|special_separator|> (219.00, 558.89) (504.00, 558.89) (504.00, 567.44) (219.00, 567.44) /F116 search, solving all board configurations within the budget. Figure 11 in <|special_separator|> (108.00, 547.98) (504.00, 547.98) (504.00, 556.53) (108.00, 556.53) /F116 the Appendix E presents the same results, but for CRTR, as well as the Contrastive and Supervised <|special_separator|> (108.00, 537.07) (147.01, 537.07) (147.01, 545.62) (108.00, 545.62) /F116 baselines. <|special_separator|> (108.00, 500.30) (120.45, 500.30) (120.45, 509.26) (108.00, 509.26) /F107 5.3 <|special_separator|> (130.42, 500.30) (216.56, 500.30) (216.56, 509.26) (130.42, 509.26) /F107 Is search necessary? <|special_separator|> (108.00, 478.95) (504.00, 478.95) (504.00, 487.50) (108.00, 487.50) /F116 Do good representations allow us to solve combinatorial problems without search, or at least reduce <|special_separator|> (108.00, 468.04) (504.00, 468.04) (504.00, 476.59) (108.00, 476.59) /F116 the amount of search required to get high success rates? We study this question by using the learned <|special_separator|> (108.00, 457.13) (448.31, 457.13) (448.31, 465.68) (108.00, 465.68) /F116 representations to perform greedy planning (see Sec. 5.1) for up to 6000 search steps. <|special_separator|> (107.53, 440.74) (504.00, 440.74) (504.00, 449.30) (107.53, 449.30) /F116 We present the results from this experiment in Figure 4, showing the fraction of problems solved with <|special_separator|> (108.00, 429.84) (504.00, 429.84) (504.00, 438.39) (108.00, 438.39) /F116 fewer than a certain number of steps. We compare to the variant of CRTR used in Sec. 5.2 that uses <|special_separator|> (108.00, 418.93) (504.00, 418.93) (504.00, 427.48) (108.00, 427.48) /F116 the representations to perform search. As an example of how to interpret this plot, the red line in the <|special_separator|> (108.00, 408.02) (504.00, 408.02) (504.00, 416.57) (108.00, 416.57) /F116 leftmost plot shows that CRTR (without search) can solve about 50% of Rubik's cube configurations <|special_separator|> (108.00, 397.11) (466.39, 397.11) (466.39, 405.66) (108.00, 405.66) /F116 in less than 300 moves. We compare to the CRL and Supervised baselines in Appendix E. <|special_separator|> (108.00, 380.72) (504.00, 380.72) (504.00, 389.27) (108.00, 389.27) /F116 On 4 / 5 tasks (Rubik's Cube, Lights Out, 15-Puzzle, and Digit Jumper), CRTR solves nearly all <|special_separator|> (108.00, 369.81) (291.32, 369.81) (291.32, 378.36) (108.00, 378.36) /F116 problem instances. The key takeaway is thus: <|special_separator|> (294.41, 369.95) (504.00, 369.95) (504.00, 378.54) (294.41, 378.54) /F134 for most problems, CRTR can find solutions without <|special_separator|> (108.00, 359.05) (209.55, 359.05) (209.55, 367.63) (108.00, 367.63) /F134 needing any search at all <|special_separator|> (209.55, 358.90) (504.00, 358.90) (504.00, 367.45) (209.55, 367.45) /F116 . Perhaps the most interesting result is the Rubik's cube, where we found <|special_separator|> (108.00, 347.99) (504.00, 347.99) (504.00, 356.54) (108.00, 356.54) /F116 that our representations can solve all problem instances in less than 6000 moves. Surprisingly, using <|special_separator|> (108.00, 337.08) (504.00, 337.08) (504.00, 345.64) (108.00, 345.64) /F116 search decreases the total fraction of Cube configurations that are solved. The main failure mode is <|special_separator|> (108.00, 326.17) (468.74, 326.17) (468.74, 334.73) (108.00, 334.73) /F116 Sokoban, where success rates are low, likely due to the presence of dead-ends in the game. <|special_separator|> (108.00, 309.79) (504.17, 309.79) (504.17, 318.34) (108.00, 318.34) /F116 However, avoiding search comes at a cost: the solutions found without search are typically longer <|special_separator|> (108.00, 298.88) (504.00, 298.88) (504.00, 307.43) (108.00, 307.43) /F116 than those found with search. For example, on the Rubik's Cube the average solution length is around <|special_separator|> (107.65, 287.97) (504.00, 287.97) (504.00, 296.52) (107.65, 296.52) /F116 400 moves (see Appendix E) - much higher than the optimal of 26 moves and even higher than the <|special_separator|> (107.25, 277.06) (327.62, 277.06) (327.62, 285.61) (107.25, 285.61) /F116 100 moves that beginner cube solving methods require. <|special_separator|> (107.69, 260.67) (504.00, 260.67) (504.00, 269.22) (107.69, 269.22) /F116 This simple greedy approach - just picking the neighbor closest to the goal - starts to show hints of <|special_separator|> (108.00, 249.76) (504.35, 249.76) (504.35, 258.31) (108.00, 258.31) /F116 algorithmic behavior. On Rubik's Cube, for example, it learns something that looks like a rudimentary <|special_separator|> (108.00, 238.85) (504.00, 238.85) (504.00, 247.40) (108.00, 247.40) /F116 form of block-building (See Fig. 5, a common strategy used by humans for solving the cube. This <|special_separator|> (455.59, 136.80) (480.56, 136.80) (480.56, 148.37) (455.59, 148.37) /F1 Step 86 <|special_separator|> (456.37, 128.58) (479.88, 128.58) (479.88, 138.54) (456.37, 138.54) /F2 Solved! <|special_separator|> (143.19, 136.80) (164.03, 136.80) (164.03, 148.37) (143.19, 148.37) /F1 Step 1 <|special_separator|> (127.25, 128.58) (179.89, 128.58) (179.89, 138.54) (127.25, 138.54) /F2 Fully scrambled. <|special_separator|> (211.41, 136.80) (236.38, 136.80) (236.38, 148.37) (211.41, 148.37) /F1 Step 16 <|special_separator|> (196.38, 128.58) (253.22, 128.58) (253.22, 138.54) (196.38, 138.54) /F2 Assembled lower <|special_separator|> (204.52, 119.99) (243.22, 119.99) (243.22, 129.95) (204.52, 129.95) /F2 2x2x2 block. <|special_separator|> (289.27, 136.80) (314.24, 136.80) (314.24, 148.37) (289.27, 148.37) /F1 Step 38 <|special_separator|> (264.78, 128.58) (340.35, 128.58) (340.35, 138.54) (264.78, 138.54) /F2 Assembled 2x2x3 block <|special_separator|> (270.42, 119.99) (334.76, 119.99) (334.76, 129.95) (270.42, 129.95) /F2 and aligned smaller <|special_separator|> (282.83, 111.27) (324.54, 111.27) (324.54, 121.23) (282.83, 121.23) /F2 1x1x3 blocks. <|special_separator|> (372.43, 136.80) (397.40, 136.80) (397.40, 148.37) (372.43, 148.37) /F1 Step 66 <|special_separator|> (353.93, 128.58) (417.59, 128.58) (417.59, 138.54) (353.93, 138.54) /F2 Almost all pieces in <|special_separator|> (350.95, 119.99) (418.77, 119.99) (418.77, 129.95) (350.95, 129.95) /F2 correct configuration. <|special_separator|> (108.00, 095.02) (143.38, 095.02) (143.38, 103.58) (108.00, 103.58) /F116 Figure 5: <|special_separator|> (146.37, 095.22) (375.33, 095.22) (375.33, 103.28) (146.37, 103.28) /F107 CRTR without search exhibits a block-building-like behavior. <|special_separator|> (378.35, 095.02) (504.00, 095.02) (504.00, 103.58) (378.35, 103.58) /F116 Intermediate states from solving <|special_separator|> (108.00, 084.12) (504.00, 084.12) (504.00, 092.67) (108.00, 092.67) /F116 a randomly scrambled cube, illustrating how the algorithm gradually builds partial structure. The <|special_separator|> (108.00, 073.21) (474.66, 073.21) (474.66, 081.76) (108.00, 081.76) /F116 average solve is about 400 moves, and we see similar block building behavior across solves. <|special_separator|> (303.51, 040.05) (308.49, 040.05) (308.49, 048.60) (303.51, 048.60) /F116 9