3 files changed, 29 insertions, 8 deletions

diff --git a/src/nissy.c b/src/nissy.c
index f933cab..5d009ba 100644
--- a/src/nissy.c
+++ b/src/nissy.c
@@ -489,6 +489,7 @@ nissy_solve(
         unsigned maxmoves,
         unsigned maxsols,
         int optimal,
+        int threads,
         unsigned long long data_size,
         const char data[data_size],
         unsigned sols_size,
@@ -499,6 +500,7 @@ nissy_solve(
         cube_t c;
         long long parse_ret;
         uint8_t h, k;
+        int t;
 
         if (solver == NULL) {
                 LOG("Error: 'solver' argument is NULL\n");
@@ -522,10 +524,22 @@ nissy_solve(
                 return 0;
         }
 
+        t = threads == 0 ? THREADS : threads;
+        if (t < 0) {
+                LOG("solve: 'threads' is negative. Please provide a "
+                    "number of threads between 1 and %d\n", THREADS);
+                return NISSY_ERROR_OPTIONS;
+        } 
+        if (t > THREADS) {
+                LOG("solve: 'threads' is above the maximum value of %d\n",
+                    THREADS);
+                return NISSY_ERROR_OPTIONS;
+        }
+
         if (!strncmp(solver, "h48", 3)) {
                 parse_ret = parse_h48_solver(solver, &h, &k);
                 if (parse_ret == NISSY_OK)
-                        return solve_h48(c, minmoves, maxmoves, maxsols,
+                        return solve_h48(c, minmoves, maxmoves, maxsols, t,
                                 data_size, data, sols_size, sols, stats);
                 else
                         return parse_ret;
diff --git a/src/nissy.h b/src/nissy.h
index 8394fad..94c604c 100644
--- a/src/nissy.h
+++ b/src/nissy.h
@@ -259,6 +259,9 @@ Parameters:
    maxsols   - The maximum number of solutions.
    optimal   - If set to a non-negative value, the maximum number of moves
                above the optimal solution length.
+   threads   - The number of threads to use. Must be less than or equalt to
+               the value of the compile-time constant THREADS. If set to 0,
+               the default value THREADS will be used.
    data_size - The size of the data buffer.
    data      - The data for the solver. Can be computed with gendata.
    sols_size - The size of the solutions buffer.
@@ -286,6 +289,7 @@ nissy_solve(
         unsigned maxmoves,
         unsigned maxsolutions,
         int optimal,
+        int threads,
         unsigned long long data_size,
         const char data[data_size],
         unsigned sols_size,
diff --git a/src/solvers/h48/solve.h b/src/solvers/h48/solve.h
index 8666007..0969c45 100644
--- a/src/solvers/h48/solve.h
+++ b/src/solvers/h48/solve.h
@@ -38,6 +38,7 @@ typedef struct {
         int64_t nodes_visited;
         int64_t table_fallbacks;
         int64_t table_lookups;
+        int threads;
         int ntasks;
         solve_h48_task_t *tasks;
         int thread_id;
@@ -62,7 +63,7 @@ STATIC int64_t solve_h48_maketasks(
     solve_h48_task_t [static STARTING_CUBES], int *);
 STATIC void *solve_h48_runthread(void *);
 STATIC int64_t solve_h48_dfs(dfsarg_solve_h48_t *);
-STATIC int64_t solve_h48(cube_t, int8_t, int8_t, uint64_t, uint64_t,
+STATIC int64_t solve_h48(cube_t, int8_t, int8_t, uint64_t, int, uint64_t,
     const void *, uint64_t, char *, long long [static NISSY_SIZE_SOLVE_STATS]);
 
 STATIC int64_t
@@ -316,7 +317,7 @@ solve_h48_runthread(void *arg)
         dfsarg = (dfsarg_solve_h48_t *)arg;
         cube = dfsarg->start_cube;
 
-        for (i = dfsarg->thread_id; i < dfsarg->ntasks; i += THREADS) {
+        for (i = dfsarg->thread_id; i < dfsarg->ntasks; i += dfsarg->threads) {
                 task = dfsarg->tasks[i];
                 memcpy(dfsarg->moves, task.moves, STARTING_MOVES);
                 dfsarg->cube = cube;
@@ -407,6 +408,7 @@ solve_h48(
         int8_t minmoves,
         int8_t maxmoves,
         uint64_t maxsolutions,
+        int threads,
         uint64_t data_size,
         const void *data,
         uint64_t solutions_size,
@@ -461,7 +463,7 @@ solve_h48(
         fallback2 = h48data + offset;
 
         symmask = symmetry_mask(cube);
-        for (i = 0; i < THREADS; i++) {
+        for (i = 0; i < threads; i++) {
                 arg[i] = (dfsarg_solve_h48_t) {
                         .start_cube = cube,
                         .cube = cube,
@@ -481,6 +483,7 @@ solve_h48(
                         .nodes_visited = 0,
                         .table_fallbacks = 0,
                         .table_lookups = 0,
+                        .threads = threads,
                         .thread_id = i,
                         .solutions_mutex = &solutions_mutex,
                 };
@@ -505,7 +508,7 @@ solve_h48(
         if (*arg[0].nsols >= (int64_t)maxsolutions)
                 goto solve_h48_done;
 
-        for (i = 0; i < THREADS; i++) {
+        for (i = 0; i < threads; i++) {
                 arg[i].ntasks = ntasks;
                 arg[i].tasks = tasks;
         }
@@ -520,12 +523,12 @@ solve_h48(
                 if (d >= 10)
                         LOG("Found %" PRId64 " solutions, searching at depth %"
                             PRId8 "\n", nsols, d);
-                for (i = 0; i < THREADS; i++) {
+                for (i = 0; i < threads; i++) {
                         arg[i].depth = d;
                         pthread_create(
                             &thread[i], NULL, solve_h48_runthread, &arg[i]);
                 }
-                for (i = 0; i < THREADS; i++)
+                for (i = 0; i < threads; i++)
                         pthread_join(thread[i], NULL);
         }
 
@@ -534,7 +537,7 @@ solve_h48_done:
                 goto solve_h48_error_solutions_buffer;
 
         nodes_visited = table_lookups = table_fallbacks = 0;
-        for (i = 0; i < THREADS; i++) {
+        for (i = 0; i < threads; i++) {
                 nodes_visited += arg[i].nodes_visited;
                 table_fallbacks += arg[i].table_fallbacks;
                 table_lookups += arg[i].table_lookups;