ENH: make multi-threading option first class citizen

Author: mstaring

src/Core/ComponentBaseClasses/elxMetricBase.hxx

@@ -156,21 +156,23 @@ MetricBase< TElastix >
       thisAsAdvanced->SetScaleGradientWithRespectToMovingImageOrientation( wrtMoving );
     }
 
-    /** Temporary?: Use the multi-threaded version or not. Default true. */
-    std::string tmp = this->m_Configuration->GetCommandLineArgument( "-mtm" ); // mtm: multi-threaded metrics
-    if( tmp == "true" || tmp == "" )
+    /** Should the metric use multi-threading? */
+    bool useMultiThreading = true;
+    this->GetConfiguration()->ReadParameter( useMultiThreading,
+      "UseMultiThreadingForMetrics", this->GetComponentLabel(), level, 0 );
+
+    thisAsAdvanced->SetUseMultiThread( useMultiThreading );
+    if( useMultiThreading )
     {
-      thisAsAdvanced->SetUseMultiThread( true );
-      std::string  tmp2        = this->m_Configuration->GetCommandLineArgument( "-threads" );
-      unsigned int nrOfThreads = atoi( tmp2.c_str() );
-      if( tmp2 != "" )
+      std::string tmp = this->m_Configuration->GetCommandLineArgument( "-threads" );
+      if( tmp != "" )
       {
+        const unsigned int nrOfThreads = atoi( tmp.c_str() );
         thisAsAdvanced->SetNumberOfThreads( nrOfThreads );
       }
     }
-    else { thisAsAdvanced->SetUseMultiThread( false ); }
 
-  } // end Advanced metric
+  } // end advanced metric
 
 } // end BeforeEachResolutionBase()