text: /* Copyright (C) 2013-2016, The Regents of The University of Michigan.
  All rights reserved.
  This software was developed in the APRIL Robotics Lab under the
  direction of Edwin Olson, ebolson@umich.edu. This software may be
  available under alternative licensing terms; contact the address above.
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:
  1. Redistributions of source code must retain the above copyright notice, this
     list of conditions and the following disclaimer.
  2. Redistributions in binary form must reproduce the above copyright notice,
     this list of conditions and the following disclaimer in the documentation
     and/or other materials provided with the distribution.
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
  ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  The views and conclusions contained in the software and documentation are those
  of the authors and should not be interpreted as representing official policies,
  either expressed or implied, of the Regents of The University of Michigan.
  */
  
  #define __USE_GNU
  #include "common/pthreads_cross.h"
  
  #include <assert.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <inttypes.h>
  #ifdef _WIN32
  #include <windows.h>
  #else
  #include <unistd.h>
  #endif
  
  #include "workerpool.h"
  #include "timeprofile.h"
  #include "math_util.h"
  #include "string_util.h"
  
  struct workerpool {
      int nthreads;
      zarray_t *tasks;
      int taskspos;
  
      pthread_t *threads;
      int *status;
  
      pthread_mutex_t mutex;
      pthread_cond_t startcond;   // used to signal the availability of work
      pthread_cond_t endcond;     // used to signal completion of all work
  
      int end_count; // how many threads are done?
  };
  
  struct task
  {
      void (*f)(void *p);
      void *p;
  };
  
  void *worker_thread(void *p)
  {
      workerpool_t *wp = (workerpool_t*) p;
  
      int cnt = 0;
  
      while (1) {
          struct task *task;
  
          pthread_mutex_lock(&wp->mutex);
          while (wp->taskspos == zarray_size(wp->tasks)) {
              wp->end_count++;
  //          printf("%"PRId64" thread %d did %d\n", utime_now(), pthread_self(), cnt);
              pthread_cond_broadcast(&wp->endcond);
              pthread_cond_wait(&wp->startcond, &wp->mutex);
              cnt = 0;
  //            printf("%"PRId64" thread %d awake\n", utime_now(), pthread_self());
          }
  
          zarray_get_volatile(wp->tasks, wp->taskspos, &task);
          wp->taskspos++;
          cnt++;
          pthread_mutex_unlock(&wp->mutex);
  //        pthread_yield();
          sched_yield();
  
          // we've been asked to exit.
          if (task->f == NULL)
              return NULL;
  
          task->f(task->p);
      }
  
      return NULL;
  }
  
  workerpool_t *workerpool_create(int nthreads)
  {
      assert(nthreads > 0);
  
      workerpool_t *wp = calloc(1, sizeof(workerpool_t));
      wp->nthreads = nthreads;
      wp->tasks = zarray_create(sizeof(struct task));
  
      if (nthreads > 1) {
          wp->threads = calloc(wp->nthreads, sizeof(pthread_t));
  
          pthread_mutex_init(&wp->mutex, NULL);
          pthread_cond_init(&wp->startcond, NULL);
          pthread_cond_init(&wp->endcond, NULL);
  
          for (int i = 0; i < nthreads; i++) {
              int res = pthread_create(&wp->threads[i], NULL, worker_thread, wp);
              if (res != 0) {
                  perror("pthread_create");
                  exit(-1);
              }
          }
      }
  
      return wp;
  }
  
  void workerpool_destroy(workerpool_t *wp)
  {
      if (wp == NULL)
          return;
  
      // force all worker threads to exit.
      if (wp->nthreads > 1) {
          for (int i = 0; i < wp->nthreads; i++)
              workerpool_add_task(wp, NULL, NULL);
  
          pthread_mutex_lock(&wp->mutex);
          pthread_cond_broadcast(&wp->startcond);
          pthread_mutex_unlock(&wp->mutex);
  
          for (int i = 0; i < wp->nthreads; i++)
              pthread_join(wp->threads[i], NULL);
  
          pthread_mutex_destroy(&wp->mutex);
          pthread_cond_destroy(&wp->startcond);
          pthread_cond_destroy(&wp->endcond);
          free(wp->threads);
      }
  
      zarray_destroy(wp->tasks);
      free(wp);
  }
  
  int workerpool_get_nthreads(workerpool_t *wp)
  {
      return wp->nthreads;
  }
  
  void workerpool_add_task(workerpool_t *wp, void (*f)(void *p), void *p)
  {
      struct task t;
      t.f = f;
      t.p = p;
  
      zarray_add(wp->tasks, &t);
  }
  
  void workerpool_run_single(workerpool_t *wp)
  {
      for (int i = 0; i < zarray_size(wp->tasks); i++) {
          struct task *task;
          zarray_get_volatile(wp->tasks, i, &task);
          task->f(task->p);
      }
  
      zarray_clear(wp->tasks);
  }
  
  // runs all added tasks, waits for them to complete.
  void workerpool_run(workerpool_t *wp)
  {
      if (wp->nthreads > 1) {
          wp->end_count = 0;
  
          pthread_mutex_lock(&wp->mutex);
          pthread_cond_broadcast(&wp->startcond);
  
          while (wp->end_count < wp->nthreads) {
  //            printf("caught %d\n", wp->end_count);
              pthread_cond_wait(&wp->endcond, &wp->mutex);
          }
  
          pthread_mutex_unlock(&wp->mutex);
  
          wp->taskspos = 0;
  
          zarray_clear(wp->tasks);
  
      } else {
          workerpool_run_single(wp);
      }
  }
  
  int workerpool_get_nprocs()
  {
  #ifdef WIN32
      SYSTEM_INFO sysinfo;
      GetSystemInfo(&sysinfo);
      return sysinfo.dwNumberOfProcessors;
  #else
      return sysconf (_SC_NPROCESSORS_ONLN);
  #endif
  }
  