From b3e16d8070ccda3a1cee98355a0afde859515f9f Mon Sep 17 00:00:00 2001
From: Kuan Bartel <kjbartel@users.noreply.github.com>
Date: Wed, 10 Feb 2016 10:37:56 +0900
Subject: [PATCH] Moved initialization of default LinearAlgebraProvider out of
 Control.ConfigureAuto to prevent unnecessary initialization and exceptions.
 Initialization code moved to new method,
 InitializeDefaultLinearAlgebraProvider(), which is called from the
 LinearAlgebraProvider getter only if the current _linearAlgebraProvider is
 null. This prevents trying to initialize multiple providers when calling any
 of the 'UseXX' methods.

---
 src/Numerics/Control.cs | 75 +++++++++++++++++++++++------------------
 1 file changed, 42 insertions(+), 33 deletions(-)

diff --git a/src/Numerics/Control.cs b/src/Numerics/Control.cs
index 4fd3fee5..de61cf4c 100644
--- a/src/Numerics/Control.cs
+++ b/src/Numerics/Control.cs
@@ -46,6 +46,7 @@ namespace MathNet.Numerics
         static int _parallelizeOrder;
         static int _parallelizeElements;
         static ILinearAlgebraProvider _linearAlgebraProvider;
+        static readonly object _staticLock = new object();
 
         static Control()
         {
@@ -64,48 +65,50 @@ namespace MathNet.Numerics
             _parallelizeOrder = 64;
             _parallelizeElements = 300;
             TaskScheduler = TaskScheduler.Default;
+        }
 
-            // Linear Algebra Provider
-#if PORTABLE
-            LinearAlgebraProvider = new ManagedLinearAlgebraProvider();
-#else
-            try
+        private static void InitializeDefaultLinearAlgebraProvider()
+        {
+            lock (_staticLock)
             {
-                var value = Environment.GetEnvironmentVariable(EnvVarLAProvider);
-                switch (value != null ? value.ToUpperInvariant() : string.Empty)
+                if (_linearAlgebraProvider == null)
                 {
 #if NATIVE
-                    case "MKL":
-                        UseNativeMKL();
-                        break;
-
-                    case "CUDA":
-                        UseNativeCUDA();
-                        break;
-
-                    case "OPENBLAS":
-                        UseNativeOpenBLAS();
-                        break;
-
-                    default:
-                        if (!TryUseNative())
+                    try
+                    {
+                        var value = Environment.GetEnvironmentVariable(EnvVarLAProvider);
+                        switch (value != null ? value.ToUpperInvariant() : string.Empty)
                         {
-                            UseManaged();
+                            case "MKL":
+                                UseNativeMKL();
+                                break;
+
+                            case "CUDA":
+                                UseNativeCUDA();
+                                break;
+
+                            case "OPENBLAS":
+                                UseNativeOpenBLAS();
+                                break;
+
+                            default:
+                                if (!TryUseNative())
+                                {
+                                    UseManaged();
+                                }
+                                break;
                         }
-                        break;
-#else
-                    default:
+                    }
+                    catch
+                    {
+                        // We don't care about any failures here at all (because "auto")
                         UseManaged();
-                        break;
+                    }
+#else
+                    UseManaged();
 #endif
                 }
             }
-            catch
-            {
-                // We don't care about any failures here at all (because "auto")
-                UseManaged();
-            }
-#endif
         }
 
         public static void UseManaged()
@@ -261,7 +264,13 @@ namespace MathNet.Numerics
         /// <value>The linear algebra provider.</value>
         public static ILinearAlgebraProvider LinearAlgebraProvider
         {
-            get { return _linearAlgebraProvider; }
+            get
+            {
+                if (_linearAlgebraProvider == null)
+                    InitializeDefaultLinearAlgebraProvider();
+
+                return _linearAlgebraProvider;
+            }
             set
             {
                 value.InitializeVerify();