first stab at the threadpool interface.

src/threadpool.h

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Copyright (c) 2016 Pedro Gonnet (pedro.gonnet@durham.ac.uk)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+#ifndef SWIFT_THREADPOOL_H
+#define SWIFT_THREADPOOL_H
+
+/* Config parameters. */
+#include "../config.h"
+
+/* Some standard headers. */
+#include <pthread.h>
+
+/* Data of a threadpool. */
+struct threadpool {
+
+  /* Number of threads in this pool. */
+  int num_threads;
+
+  /* The threads themselves. */
+  pthread_t *threads;
+
+  /* This is where threads go to rest. */
+  pthread_mutex_t sleep_mutex;
+  pthread_cond_t sleep_cond;
+  
+  /* Current map data and count. */
+  void *map_data;
+  size_t map_data_count, map_data_size, map_data_stride;
+};
+
+/* Function prototypes. */
+void threadpool_init(struct threadpool *tp, int num_threads);
+void threadpool_map(struct threadpool *tp, void *map_data, size_t N, int stride,
+                    void *extra_data);
+
+#endif /* SWIFT_THREADPOOL_H */