From e965a9697735f964c0bd8e667777458e80f21313 Mon Sep 17 00:00:00 2001
From: heister <heister@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Wed, 2 Oct 2013 17:40:15 +0000
Subject: [PATCH] introduce new n_threads(), deprecate n_default_threads

git-svn-id: https://svn.dealii.org/trunk@31073 0785d39b-7218-0410-832d-ea1e28bc413d
---
 deal.II/doc/news/changes.h                    |  7 ++++++
 .../include/deal.II/base/multithread_info.h   | 11 ++++++++-
 deal.II/source/base/multithread_info.cc       | 24 ++++++++++++++-----
 3 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/deal.II/doc/news/changes.h b/deal.II/doc/news/changes.h
index bb840cebeb..4cd8154509 100644
--- a/deal.II/doc/news/changes.h
+++ b/deal.II/doc/news/changes.h
@@ -61,6 +61,13 @@ inconvenience this causes.
 
 
 <ol>
+  <li>
+  Changed: if configured with TBB but the number of threads is set to 1,
+  do not bother to use TBB in workstream.
+  <br>
+  (Timo Heister, 2013/10/02)
+  </li>
+
   <li>
   New: step-51 demonstrates the use of hybridized discontinuous Galerkin
   methods in deal.II, using the face elements FE_FaceQ. The programs solves a
diff --git a/deal.II/include/deal.II/base/multithread_info.h b/deal.II/include/deal.II/base/multithread_info.h
index 3b72975556..38a3f21464 100644
--- a/deal.II/include/deal.II/base/multithread_info.h
+++ b/deal.II/include/deal.II/base/multithread_info.h
@@ -86,8 +86,17 @@ public:
    * At start time this is <tt>n_cpus</tt> or
    * one, if detection of the number
    * of CPUs is not possible.
+   *
+   * @deprecated: use set_thread_limit() instead.
+   */
+  unsigned int n_default_threads DEAL_II_DEPRECATED;
+
+  /*
+   * Returns the number of threads to use. This is governed by the number
+   * of cores the system has and can be further restricted by
+   * set_thread_limit().
    */
-  unsigned int n_default_threads;
+  unsigned int n_threads() const;
 
   /**
    * Determine an estimate for
diff --git a/deal.II/source/base/multithread_info.cc b/deal.II/source/base/multithread_info.cc
index e79373d0aa..6ea0b132a6 100644
--- a/deal.II/source/base/multithread_info.cc
+++ b/deal.II/source/base/multithread_info.cc
@@ -101,6 +101,9 @@ unsigned int MultithreadInfo::get_n_cpus()
 
 void MultithreadInfo::set_thread_limit(const unsigned int max_threads)
 {
+  Assert(n_max_threads==numbers::invalid_unsigned_int,
+      ExcMessage("Calling set_thread_limit() more than once is not supported!"));
+
   unsigned int max_threads_env = numbers::invalid_unsigned_int;
   char *penv;
   penv = getenv ("DEAL_II_NUM_THREADS");
@@ -117,11 +120,13 @@ void MultithreadInfo::set_thread_limit(const unsigned int max_threads)
     }
 }
 
-bool MultithreadInfo::is_running_single_threaded()
+
+unsigned int MultithreadInfo::n_threads() const
 {
   if (n_max_threads == numbers::invalid_unsigned_int)
-    n_max_threads = tbb::task_scheduler_init::default_num_threads();
-  return n_max_threads == 1;
+    return tbb::task_scheduler_init::default_num_threads();
+  else
+    return n_max_threads;
 }
 
 
@@ -132,9 +137,9 @@ unsigned int MultithreadInfo::get_n_cpus()
   return 1;
 }
 
-bool MultithreadInfo::is_running_single_threaded()
+unsigned int MultithreadInfo::n_threads() const
 {
-  return true;
+  return 1;
 }
 
 void MultithreadInfo::set_thread_limit(const unsigned int)
@@ -144,10 +149,17 @@ void MultithreadInfo::set_thread_limit(const unsigned int)
 #endif
 
 
+bool MultithreadInfo::is_running_single_threaded()
+{
+  return n_threads() == 1;
+}
+
+
 MultithreadInfo::MultithreadInfo ()
   :
   n_cpus (get_n_cpus()),
-  n_default_threads (n_cpus)
+  n_default_threads (n_cpus),
+  n_max_threads (numbers::invalid_unsigned_int)
 {}
 
 
-- 
2.39.5