tweaked work[0] return value

src/Numerics/Algorithms/LinearAlgebra/ManagedLinearAlgebraProvider.cs

@@ -1053,6 +1053,8 @@ namespace MathNet.Numerics.Algorithms.LinearAlgebra
             {
                 ComputeQR(work, i, q, rRows, i, rRows - 1, i, rRows - 1);
             }
+
+            work[0] = rRows * rRows;
         }
 
         #region QR Factor Helper functions
@@ -1265,11 +1267,14 @@ namespace MathNet.Numerics.Algorithms.LinearAlgebra
 
             if (work.Length < rRows * rRows)
             {
-                throw new ArgumentException(Resources.ArgumentArraysSameLength, "work");
+                work[0] = rRows * rRows;
+                throw new ArgumentException(Resources.WorkArrayTooSmall, "work");
             }
 
             QRFactor(r, rRows, rColumns, q, work);
             QRSolveFactored(q, r, rRows, rColumns, b, bColumns, x);
+
+            work[0] = rRows * rRows;
         }
 
         /// <summary>

src/Numerics/Properties/Resources.Designer.cs

@@ -635,5 +635,14 @@ namespace MathNet.Numerics.Properties {
                 return ResourceManager.GetString("UserDefinedProviderNotSpecified", resourceCulture);
             }
         }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to The given work array is too small. Check work[0] for the corret size..
+        /// </summary>
+        internal static string WorkArrayTooSmall {
+            get {
+                return ResourceManager.GetString("WorkArrayTooSmall", resourceCulture);
+            }
+        }
     }
 }