Comment on initialisation of xCorr in ILU smoother

src/foam/matrices/blockLduMatrix/BlockLduSmoothers/BlockILUSmoother/BlockILUSmoother.H

@@ -121,6 +121,12 @@ public:
                     residual_[i] = b[i] - residual_[i];
                 }
 
+                // Note.
+                // For the ILU smoother it is not necessary to initialise
+                // xCorr to zero, because it gets over-written by the product
+                // but for more complex smoothers it is
+                // HJ, 15/Jun/2017
+                // xCorr_ = pTraits<Type>::zero;
                 precon_.precondition(xCorr_, residual_);
 
                 // Add correction to x