4 files changed, 309 insertions, 5 deletions

diff --git a/src/nissy.c b/src/nissy.c
index e610199..44efb83 100644
--- a/src/nissy.c
+++ b/src/nissy.c
@@ -1,5 +1,6 @@
 #include <inttypes.h>
 #include <pthread.h>
+#include <stdatomic.h>
 #include <stdarg.h>
 #include <stdbool.h>
 #include <string.h>
@@ -401,8 +402,9 @@ nissy_solve(
                         LOG("gendata: could not parse options\n");
                         ret = -1;
                 } else {
-                        ret = solve_h48(c, minmoves, maxmoves, maxsolutions,
-                            data, solutions);
+                        ret = THREADS > 1 ?
+                                solve_h48_multithread(c, minmoves, maxmoves, maxsolutions, data, solutions) :
+                                solve_h48(c, minmoves, maxmoves, maxsolutions, data, solutions);
                 }
         } else if (!strcmp(solver, "h48stats")) {
                 ret = solve_h48stats(c, maxmoves, data, solutions);
diff --git a/src/solvers/h48/h48.h b/src/solvers/h48/h48.h
index 18153d1..176ce22 100644
--- a/src/solvers/h48/h48.h
+++ b/src/solvers/h48/h48.h
@@ -4,3 +4,4 @@
 #include "gendata_h48.h"
 #include "stats.h"
 #include "solve.h"
+#include "solve_multithread.h"
diff --git a/src/solvers/h48/solve.h b/src/solvers/h48/solve.h
index b67aedc..c2dce91 100644
--- a/src/solvers/h48/solve.h
+++ b/src/solvers/h48/solve.h
@@ -4,7 +4,7 @@ typedef struct {
         int8_t nmoves;
         int8_t depth;
         uint8_t moves[MAXLEN];
-        int64_t *nsols;
+        _Atomic int64_t *nsols;
         int64_t maxsolutions;
         uint8_t h;
         uint8_t k;
@@ -167,7 +167,7 @@ solve_h48(
         char *solutions
 )
 {
-        int64_t nsols;
+        _Atomic int64_t nsols;
         dfsarg_solveh48_t arg;
         tableinfo_t info;
 
@@ -199,6 +199,7 @@ solve_h48(
                 arg.npremoves = 0;
                 solve_h48_dfs(&arg);
         }
-
+        **arg.nextsol = '\0';
+        (*arg.nextsol)++;
         return nsols;
 }
diff --git a/src/solvers/h48/solve_multithread.h b/src/solvers/h48/solve_multithread.h
new file mode 100644
index 0000000..86171a9
--- /dev/null
+++ b/src/solvers/h48/solve_multithread.h
@@ -0,0 +1,300 @@
+#define MAX_QUEUE_SIZE 244
+#define BFS_DEPTH 2
+
+typedef struct {
+        dfsarg_solveh48_t tasks[MAX_QUEUE_SIZE];
+        int front;
+        int rear;
+        int tasks_count;
+        int active;
+        pthread_mutex_t mutex;
+        pthread_cond_t cond;
+        pthread_cond_t active_cond;
+        atomic_bool terminate;
+} task_queue_t;
+
+STATIC void solve_h48_appendsolution_thread(dfsarg_solveh48_t *, task_queue_t *);
+STATIC void init_queue(task_queue_t *);
+STATIC void submit_task(task_queue_t *, dfsarg_solveh48_t);
+STATIC void copy_queue(task_queue_t *, task_queue_t *, int, _Atomic int64_t *);
+STATIC void *start_thread(void *);
+STATIC int64_t solve_h48_bfs(dfsarg_solveh48_t *, task_queue_t *, int8_t);
+STATIC int64_t solve_h48_single(dfsarg_solveh48_t *, task_queue_t *);
+STATIC int64_t solve_h48_multithread(cube_t, int8_t, int8_t, int8_t, const void *, char *);
+
+STATIC void
+solve_h48_appendsolution_thread(dfsarg_solveh48_t *arg, task_queue_t *tq)
+{
+        pthread_mutex_lock(&tq->mutex);
+        int strl = 0;
+        uint8_t invertedpremoves[MAXLEN];
+        char *solution = *arg->nextsol;
+
+        strl = writemoves(arg->moves, arg->nmoves, *arg->nextsol);
+        *arg->nextsol += strl;
+
+        if (arg->npremoves)
+        {
+                **arg->nextsol = ' ';
+                (*arg->nextsol)++;
+
+                invertmoves(arg->premoves, arg->npremoves, invertedpremoves);
+                strl = writemoves(invertedpremoves, arg->npremoves, *arg->nextsol);
+                *arg->nextsol += strl;
+        }
+        LOG("Solution found: %s\n", solution);
+
+        **arg->nextsol = '\n';
+        (*arg->nextsol)++;
+        (*arg->nsols)++;
+        pthread_mutex_unlock(&tq->mutex);
+}
+
+STATIC void
+init_queue(task_queue_t *queue)
+{
+        queue->front = 0;
+        queue->rear = 0;
+        queue->tasks_count = 0;
+        queue->active = 0;
+        queue->terminate = ATOMIC_VAR_INIT(false);
+        pthread_mutex_init(&queue->mutex, NULL);
+        pthread_cond_init(&queue->cond, NULL);
+        pthread_cond_init(&queue->active_cond, NULL);
+}
+
+STATIC void
+submit_task(task_queue_t *queue, dfsarg_solveh48_t task)
+{
+        pthread_mutex_lock(&queue->mutex);
+        queue->tasks[queue->rear] = task;
+        queue->rear = (queue->rear + 1) % MAX_QUEUE_SIZE;
+        queue->tasks_count++;
+        pthread_cond_broadcast(&queue->cond);
+        pthread_mutex_unlock(&queue->mutex);
+}
+
+STATIC void
+copy_queue(task_queue_t *src, task_queue_t *dest, int depth, _Atomic int64_t *nsols)
+{
+        pthread_mutex_lock(&dest->mutex);
+        for (int i = src->front; i != src->rear; i = (i + 1) % MAX_QUEUE_SIZE)
+        {
+                        dest->tasks[i] = src->tasks[i];
+                        dest->tasks[i].depth = depth;
+        }
+        dest->front = src->front;
+        dest->rear = src->rear;
+        dest->tasks_count = src->tasks_count;
+        pthread_cond_broadcast(&dest->cond);
+        pthread_mutex_unlock(&dest->mutex);
+}
+
+STATIC void *
+start_thread(void *arg)
+{
+        task_queue_t *queue = (task_queue_t *)arg;
+        while (1) {
+                pthread_mutex_lock(&queue->mutex);
+                while (queue->tasks_count == 0 && !queue->terminate) {
+                        pthread_cond_wait(&queue->cond, &queue->mutex);
+                }
+                if (queue->tasks_count == 0 && queue->terminate) {
+                        pthread_mutex_unlock(&queue->mutex);
+                        break;
+                }
+
+                if (queue->tasks_count > 0) {
+                        dfsarg_solveh48_t task = queue->tasks[queue->front];
+                        queue->front = (queue->front + 1) % MAX_QUEUE_SIZE;
+                        queue->tasks_count--;
+                        queue->active++;
+                        pthread_mutex_unlock(&queue->mutex);
+                        
+                        solve_h48_single(&task, queue);
+
+                        pthread_mutex_lock(&queue->mutex);
+                        queue->active--;
+
+                        if(queue->tasks_count == 0 && queue->active == 0)
+                                pthread_cond_signal(&queue->active_cond);
+                }
+                pthread_mutex_unlock(&queue->mutex);
+        }
+        return NULL;
+}
+
+STATIC int64_t
+solve_h48_bfs(dfsarg_solveh48_t *arg_zero, task_queue_t *tq, int8_t maxmoves)
+{
+        dfsarg_solveh48_t queue[MAX_QUEUE_SIZE];
+        int front = 0, rear = 0;
+        dfsarg_solveh48_t nextarg;
+        int depth = 0;
+        int nodes_at_current_depth = 1;
+        int nodes_at_next_depth = 0;
+        queue[rear++] = *arg_zero;
+
+        dfsarg_solveh48_t task_pool[MAX_QUEUE_SIZE];
+
+        while (front < rear){
+                dfsarg_solveh48_t arg = queue[front++];
+                nodes_at_current_depth--;
+
+                if (*arg.nsols == arg.maxsolutions)
+                        return 1;
+
+                if (issolved(arg.cube)){
+                        if (arg.nmoves + arg.npremoves >= arg.depth && arg.nmoves + arg.npremoves <= maxmoves)
+                        solve_h48_appendsolution(&arg);
+                        continue;
+                }
+
+                arg.nissbranch = MM_NORMAL;
+                uint32_t allowed = allowednextmove_h48(arg.moves, arg.nmoves, arg.nissbranch);
+
+                for (uint8_t m = 0; m < 18; m++){
+                        if (allowed & (1 << m)){
+                                nextarg = arg;
+                                nextarg.nmoves = arg.nmoves + 1;
+                                nextarg.moves[arg.nmoves] = m;
+                                nextarg.cube = move(arg.cube, m);
+                                nextarg.inverse = premove(arg.inverse, m);
+
+                                if (nextarg.nmoves == BFS_DEPTH){
+                                        dfsarg_solveh48_t *task = &task_pool[rear % MAX_QUEUE_SIZE];
+                                        *task = nextarg;
+                                        submit_task(tq, *task);
+                                } else {
+                                        queue[rear++] = nextarg;
+                                        nodes_at_next_depth++;
+                                }
+                        }
+                }
+                if (nodes_at_current_depth == 0){
+                        nodes_at_current_depth = nodes_at_next_depth;
+                        nodes_at_next_depth = 0;
+                        LOG("Found %" PRId64 " solutions, searching at depth %" PRId8 "\n", *nextarg.nsols, depth++);
+                }
+                if (depth == BFS_DEPTH) return 0;
+        }
+        return 1;
+}
+
+STATIC int64_t
+solve_h48_single(dfsarg_solveh48_t *arg, task_queue_t *tq)
+{
+        dfsarg_solveh48_t nextarg;
+        int64_t ret;
+        uint8_t m;
+
+        if (*arg->nsols == arg->maxsolutions)
+                return 0;
+
+        if (solve_h48_stop(arg))
+                return 0;
+
+        if (issolved(arg->cube)){
+                if (arg->nmoves + arg->npremoves != arg->depth)
+                        return 0;
+                solve_h48_appendsolution_thread(arg, tq);
+                return 1;
+        }
+
+        nextarg = *arg;
+        ret = 0;
+        uint32_t allowed;
+        if (arg->nissbranch & MM_INVERSE){
+                allowed = allowednextmove_h48(arg->premoves, arg->npremoves, arg->nissbranch);
+                for (m = 0; m < 18; m++){
+                        if (allowed & (1 << m)){
+                                nextarg.npremoves = arg->npremoves + 1;
+                                nextarg.premoves[arg->npremoves] = m;
+                                nextarg.inverse = move(arg->inverse, m);
+                                nextarg.cube = premove(arg->cube, m);
+                                ret += solve_h48_single(&nextarg, tq);
+                        }
+                }
+        } else {
+                allowed = allowednextmove_h48(arg->moves, arg->nmoves, arg->nissbranch);
+                for (m = 0; m < 18; m++){
+                        if (allowed & (1 << m)){
+                                nextarg.nmoves = arg->nmoves + 1;
+                                nextarg.moves[arg->nmoves] = m;
+                                nextarg.cube = move(arg->cube, m);
+                                nextarg.inverse = premove(arg->inverse, m);
+                                ret += solve_h48_single(&nextarg, tq);
+                        }
+                }
+        }
+        return ret;
+}
+
+STATIC int64_t
+solve_h48_multithread(
+        cube_t cube,
+        int8_t minmoves,
+        int8_t maxmoves,
+        int8_t maxsolutions,
+        const void *data,
+        char *solutions)
+{
+        _Atomic int64_t nsols = 0;
+        int p_depth = 0;
+        dfsarg_solveh48_t arg;
+        tableinfo_t info;
+        pthread_t threads[THREADS];
+
+        if (!readtableinfo_n(data, 2, &info)){
+                LOG("solve_h48: error reading table\n");
+                return 0;
+        }
+
+        arg = (dfsarg_solveh48_t){
+                .cube = cube,
+                .inverse = inverse(cube),
+                .nsols = &nsols,
+                .depth = minmoves,
+                .maxsolutions = maxsolutions,
+                .h = info.h48h,
+                .k = info.bits,
+                .cocsepdata = get_cocsepdata_ptr(data),
+                .h48data = get_h48data_ptr(data),
+                .nextsol = &solutions};
+
+        task_queue_t q;
+        init_queue(&q);
+        if (solve_h48_bfs(&arg, &q, maxmoves))
+                return nsols;
+
+        task_queue_t nq;
+        init_queue(&nq);
+
+        for (int i = 0; i < THREADS; i++){
+                pthread_create(&threads[i], NULL, &start_thread, &nq);
+        }
+
+        nsols = 0;
+        for (p_depth = minmoves > BFS_DEPTH ? minmoves : BFS_DEPTH;
+                 p_depth <= maxmoves && nsols < maxsolutions;
+                 p_depth++)
+        {
+                LOG("Found %" PRId64 " solutions, searching at depth %" PRId8 "\n", nsols, p_depth);
+                copy_queue(&q, &nq, p_depth, &nsols);
+                
+                pthread_mutex_lock(&nq.mutex);
+                while (nq.active > 0 || nq.tasks_count > 0)
+                        pthread_cond_wait(&nq.active_cond, &nq.mutex);
+                pthread_mutex_unlock(&nq.mutex);
+        }
+
+        atomic_store(&nq.terminate, true);
+        pthread_cond_broadcast(&nq.cond);
+
+        for (int i = 0; i < THREADS; i++){
+                pthread_join(threads[i], NULL);
+        }
+        **arg.nextsol = '\0';
+        (*arg.nextsol)++;
+        return nsols;
+}