From 0550a16c1cce868bbc3f3b5ad59f80e35cf2a6cd Mon Sep 17 00:00:00 2001
From: Sebastiano Tronto <sebastiano@tronto.net>
Date: Wed, 19 Mar 2025 17:16:41 +0100
Subject: Filter solutions for coordinate solver and fix ordering

---
 src/core/moves.h                 | 28 ++++++++++++++++++++++++++++
 src/solvers/coord/eo.h           |  1 +
 src/solvers/coord/solve.h        |  8 +++++---
 src/solvers/coord/types_macros.h |  1 +
 4 files changed, 35 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/core/moves.h b/src/core/moves.h
index 3a1158b..a45bc05 100644
--- a/src/core/moves.h
+++ b/src/core/moves.h
@@ -6,6 +6,8 @@ STATIC_INLINE uint32_t allowednextmove_mask(uint8_t *, uint8_t);
 
 STATIC_INLINE uint8_t movebase(uint8_t);
 STATIC_INLINE uint8_t moveaxis(uint8_t);
+STATIC_INLINE bool isbase(uint8_t);
+STATIC_INLINE bool parallel(uint8_t, uint8_t);
 STATIC_INLINE uint32_t disable_moves(uint32_t, uint8_t);
 
 STATIC cube_t move(cube_t, uint8_t);
@@ -13,6 +15,7 @@ STATIC cube_t premove(cube_t, uint8_t);
 STATIC uint8_t inverse_move(uint8_t);
 STATIC void invertmoves(uint8_t *, uint8_t, uint8_t *);
 STATIC void sortparallel(uint8_t *, uint8_t);
+STATIC bool are_lastmoves_singlecw(int n, uint8_t [n]);
 
 STATIC int readmoves(const char *, int, uint8_t *);
 STATIC cube_t applymoves(cube_t, const char *);
@@ -91,6 +94,18 @@ moveaxis(uint8_t move)
 	return move / 6;
 }
 
+STATIC_INLINE bool
+isbase(uint8_t move)
+{
+	return move == 3 * movebase(move);
+}
+
+STATIC_INLINE bool
+parallel(uint8_t m1, uint8_t m2)
+{
+	return moveaxis(m1) == moveaxis(m2);
+}
+
 STATIC_INLINE uint8_t
 moveopposite(uint8_t move)
 {
@@ -241,6 +256,19 @@ sortparallel(uint8_t *moves, uint8_t n)
 			SWAP(moves[i], moves[i+1]);
 }
 
+STATIC bool
+are_lastmoves_singlecw(int n, uint8_t moves[n])
+{
+	bool two;
+
+	if (n == 0)
+		return true;
+
+	two = n > 1 && parallel(moves[n-1], moves[n-2]);
+
+	return isbase(moves[n-1]) && (!two || isbase(moves[n-2]));
+}
+
 STATIC int
 readmoves(const char *buf, int max, uint8_t *ret)
 {
diff --git a/src/solvers/coord/eo.h b/src/solvers/coord/eo.h
index 449397f..46a6f70 100644
--- a/src/solvers/coord/eo.h
+++ b/src/solvers/coord/eo.h
@@ -15,6 +15,7 @@ STATIC coord_t coordinate_eo = {
 		[AXIS_RL] = TRANS_URr,
 		[AXIS_FB] = TRANS_UFr,
 	},
+	.is_admissible = &are_lastmoves_singlecw,
 };
 
 STATIC uint64_t
diff --git a/src/solvers/coord/solve.h b/src/solvers/coord/solve.h
index 73ae9b1..6903d1e 100644
--- a/src/solvers/coord/solve.h
+++ b/src/solvers/coord/solve.h
@@ -35,15 +35,17 @@ solve_coord_appendsolution(dfsarg_solve_coord_t *arg)
 	char *m;
 
 	if (*arg->nsols >= arg->maxsolutions ||
-	    arg->nmoves > *arg->shortest_sol + arg->optimal)
+	    arg->nmoves > *arg->shortest_sol + arg->optimal ||
+	    (arg->coord->is_admissible != NULL &&
+	        !arg->coord->is_admissible(arg->nmoves, arg->moves)))
 		return 0;
 
-	sortparallel(arg->moves, arg->nmoves);
-
 	t = inverse_trans(arg->trans);
 	for (i = 0; i < arg->nmoves; i++)
 		tmoves[i] = transform_move(arg->moves[i], t);
 
+	sortparallel(tmoves, arg->nmoves);
+
 	l = arg->solutions_size - *arg->solutions_used;
 	m = *arg->solutions + *arg->solutions_used;
 	strl = writemoves(tmoves, arg->nmoves, l, m);
diff --git a/src/solvers/coord/types_macros.h b/src/solvers/coord/types_macros.h
index 84085ad..2309efc 100644
--- a/src/solvers/coord/types_macros.h
+++ b/src/solvers/coord/types_macros.h
@@ -11,4 +11,5 @@ typedef struct {
 	uint32_t moves_mask;
 	uint64_t trans_mask;
 	uint8_t axistrans[3];
+	bool (*is_admissible)(int n, uint8_t [n]);
 } coord_t;
-- 
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