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#include "solve.h"
/* Data for creating a pruning table:
- compressed: if set to true, each entry occupies only 4 bits, but values
larger than 15 cannot be stored.
- available[] is the list of availabel moves, as above.
- *ptable is the actual table to fill.
- n is the number of states (size of ptable).
- index must "linearize" the cube, i.e. return its index in ptable.
- fname is the name of the file where to store the table */
typedef struct {
bool compressed, *available;
int max_moves;
uint8_t *ptable;
uint64_t n;
uint64_t (*index)(Cube);
char *fname;
} PruneData;
/* TODO: comment this */
typedef struct {
bool niss;
int m, d;
uint64_t *n;
Move last1, last2;
} DfsData;
void solve_dfs(Cube cube, SolveData *sd, DfsData dd);
void init_ptable(PruneData *pd, bool read, bool write);
/* Search solutions of lenght exactly d */
void solve_dfs(Cube cube, SolveData *sd, DfsData dd) {
if (*dd.n >= sd->max_solutions ||
((!sd->can_niss || dd.niss) && dd.m + sd->f(cube) > dd.d))
return;
(sd->solutions[*dd.n][dd.m]).inverse = dd.niss;
(sd->solutions[*dd.n][dd.m]).m = NULLMOVE;
if (!sd->f(cube)) { /* Solved */
if (dd.m == dd.d) {
(*dd.n)++;
if (*dd.n < sd->max_solutions)
copy_alg(sd->solutions[*dd.n-1], sd->solutions[*dd.n]);
}
return;
}
for (int i = 0; i < NMOVES && sd->sorted_moves[i] != NULLMOVE; i++) {
Move move = sd->sorted_moves[i];
if (possible_next[dd.last2][dd.last1][move]) {
sd->solutions[*dd.n][dd.m].inverse = dd.niss;
sd->solutions[*dd.n][dd.m].m = move;
DfsData nn = { .niss = dd.niss, .m = dd.m+1, .d = dd.d, .n = dd.n,
.last1 = move, .last2 = dd.last1 };
solve_dfs(move_cube(move, cube), sd, nn);
}
}
if (sd->can_niss && !dd.niss &&
(!dd.m || (dd.m && sd->f(move_cube(dd.last1, (Cube){0}))))) {
DfsData nn = { .niss = true, .m = dd.m, .d = dd.d, .n = dd.n };
solve_dfs(inverse_cube(cube), sd, nn);
}
}
/* Iterative deepening depth-first search: for i running from the minimum
to the maximum number of moves allowed, looks for solutions of length i. */
int solve(Cube cube, SolveData *sd) {
if (sd->precondition != NULL && !sd->precondition(cube))
return -1;
/* If not given, generate sorted list of moves */
if (sd->sorted_moves[0] == NULLMOVE) {
int a[NMOVES], b[NMOVES], ia = 0, ib = 0;
for (int i = 0; i < NMOVES; i++) {
if (sd->available[i]) {
if (sd->f(move_cube(i, (Cube){0})))
a[ia++] = i;
else
b[ib++] = i;
}
}
intarrcopy(a, (int *)sd->sorted_moves, ia);
intarrcopy(b, (int *)sd->sorted_moves+ia, ib);
sd->sorted_moves[ia+ib] = NULLMOVE;
}
sd->max_solutions = min(sd->max_solutions, MAXS);
/*TODO
Cube rotated = apply_alg(sd->pre_rotation, (Cube){0});
cube = apply_alg(inverse_cube(rotated), compose(cube, rotated));
*/
uint64_t ret = 0;
for (int i=sd->min_moves; i<=sd->max_moves&&!(ret&&sd->optimal_only); i++) {
DfsData dd = { .d = i, .n = &ret };
solve_dfs(cube, sd, dd);
}
/* TODO: transform solutions with inverse of pre_rotation */
/*
for (uint64_t i = 0; i < ret; i++) {
if (sd->cleanup)
cleanup(sd->solutions[i], sd->max_moves*3);
}*/
return ret;
}
void prune_dfs(Cube cube, PruneData *pd, DfsData dd) {
uint64_t ind = pd->index(cube);
if ((!ind || pd->ptable[ind]) && pd->ptable[ind] != dd.m)
return;
if (dd.m == dd.d) {
if (ind && !pd->ptable[ind]) {
pd->ptable[ind] = dd.m;
(*dd.n)++;
}
return;
}
for (int i = 0; i < NMOVES; i++) {
if (dd.m<20)
if (possible_next[dd.last2][dd.last1][i] && pd->available[i]) {
DfsData nn = { .m = dd.m+1, .d = dd.d, .n = dd.n,
.last1 = i, .last2 = dd.last1 };
prune_dfs(move_cube(i, cube), pd, nn);
}
}
}
void init_ptable(PruneData *pd, bool read, bool write) {
if (read) {
FILE *ptf;
if ((ptf = fopen(pd->fname, "rb")) != NULL) {
uint64_t r = fread(pd->ptable, sizeof(uint8_t), pd->n, ptf);
fclose(ptf);
if (r == pd->n) return;
}
}
/* TODO: for now it behaves always as if copressed = false */
for (uint64_t i = 0; i < pd->n; i++)
pd->ptable[i] = 0;
uint64_t s = 1;
for (int i = 1; i < pd->max_moves && s < pd->n; i++) {
DfsData dd = { .d = i, .n = &s };
prune_dfs((Cube){0}, pd, dd);
}
if (write) {
FILE *ptf;
if ((ptf = fopen(pd->fname, "wb")) != NULL) {
fwrite(pd->ptable, sizeof(uint8_t), pd->n, ptf);
fclose(ptf);
return;
}
}
}
/* Solving steps (and indexing functions) */
uint64_t index_eofb(Cube cube) { return cube.eofb; }
int f_eofb(Cube cube) {
static bool initialized_ptable;
static uint8_t pt_eofb[pow2to11];
if (!initialized_ptable) {
PruneData pd = {
.compressed = false, .available = standard_moveset, .max_moves = 13,
.ptable = pt_eofb, .n = pow2to11, .index = index_eofb,
.fname = "ptable_eofb"
};
init_ptable(&pd, false, true);
initialized_ptable = true;
}
return cube.eofb ? pt_eofb[cube.eofb] : 0;
}
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