From 4946d758c932ea218046371cb94b15451107b957 Mon Sep 17 00:00:00 2001
From: Chris Jones <cdj@fnal.gov>
Date: Fri, 20 Nov 2015 19:58:08 +0100
Subject: [PATCH] Use a class constructor to initialize CPU cache sizes

Using a static instance of a class to initialize the values for
the CPU cache sizes guarantees thread-safe initialization of the
values when using C++11. Therefore under C++11 it is no longer
necessary to call Eigen::initParallel() before calling any eigen
functions on different threads.
---
 .../Core/products/GeneralBlockPanelKernel.h   | 41 ++++++++++---------
 1 file changed, 22 insertions(+), 19 deletions(-)

diff --git a/Eigen/src/Core/products/GeneralBlockPanelKernel.h b/Eigen/src/Core/products/GeneralBlockPanelKernel.h
index 79eaa7432..94754bf66 100644
--- a/Eigen/src/Core/products/GeneralBlockPanelKernel.h
+++ b/Eigen/src/Core/products/GeneralBlockPanelKernel.h
@@ -36,37 +36,40 @@ const std::ptrdiff_t defaultL3CacheSize = 512*1024;
 #endif
 
 /** \internal */
-inline void manage_caching_sizes(Action action, std::ptrdiff_t* l1, std::ptrdiff_t* l2, std::ptrdiff_t* l3)
-{
-  static bool m_cache_sizes_initialized = false;
-  static std::ptrdiff_t m_l1CacheSize = 0;
-  static std::ptrdiff_t m_l2CacheSize = 0;
-  static std::ptrdiff_t m_l3CacheSize = 0;
-
-  if(!m_cache_sizes_initialized)
-  {
+struct CacheSizes { 
+  CacheSizes(): m_l1(-1),m_l2(-1),m_l3(-1) {
     int l1CacheSize, l2CacheSize, l3CacheSize;
     queryCacheSizes(l1CacheSize, l2CacheSize, l3CacheSize);
-    m_l1CacheSize = manage_caching_sizes_helper(l1CacheSize, defaultL1CacheSize);
-    m_l2CacheSize = manage_caching_sizes_helper(l2CacheSize, defaultL2CacheSize);
-    m_l3CacheSize = manage_caching_sizes_helper(l3CacheSize, defaultL3CacheSize);
-    m_cache_sizes_initialized = true;
+    m_l1 = manage_caching_sizes_helper(l1CacheSize, defaultL1CacheSize);
+    m_l2 = manage_caching_sizes_helper(l2CacheSize, defaultL2CacheSize);
+    m_l3 = manage_caching_sizes_helper(l3CacheSize, defaultL3CacheSize);
   }
 
+  std::ptrdiff_t m_l1;
+  std::ptrdiff_t m_l2;
+  std::ptrdiff_t m_l3;
+};
+
+
+/** \internal */
+inline void manage_caching_sizes(Action action, std::ptrdiff_t* l1, std::ptrdiff_t* l2, std::ptrdiff_t* l3)
+{
+  static CacheSizes m_cacheSizes;
+
   if(action==SetAction)
   {
     // set the cpu cache size and cache all block sizes from a global cache size in byte
     eigen_internal_assert(l1!=0 && l2!=0);
-    m_l1CacheSize = *l1;
-    m_l2CacheSize = *l2;
-    m_l3CacheSize = *l3;
+    m_cacheSizes.m_l1 = *l1;
+    m_cacheSizes.m_l2 = *l2;
+    m_cacheSizes.m_l3 = *l3;
   }
   else if(action==GetAction)
   {
     eigen_internal_assert(l1!=0 && l2!=0);
-    *l1 = m_l1CacheSize;
-    *l2 = m_l2CacheSize;
-    *l3 = m_l3CacheSize;
+    *l1 = m_cacheSizes.m_l1;
+    *l2 = m_cacheSizes.m_l2;
+    *l3 = m_cacheSizes.m_l3;
   }
   else
   {