Merge branch 'matrix-improvements' into 'master'

Various matrix improvements

See merge request !42

src/SparseTransform/DataStructures/DoubleMatrix.cs

+using System.Text;
+
 namespace SparseTransform.DataStructures
 {
     /// <summary>
@@ -41,7 +43,7 @@ namespace SparseTransform.DataStructures
         /// <returns>MatrixMarket String</returns>
         public String ToMatrixMarketString()
         {
-            String MMString;
+            StringBuilder MMString = new StringBuilder();
             String type = "real";
             String symmetry;
             if (Symmetric)
@@ -53,42 +55,19 @@ namespace SparseTransform.DataStructures
                 symmetry = "general";
             }
             // Build header
-            MMString = $"%%MatrixMarket matrix coordinate {type} {symmetry}\n";
+            MMString.Append($"%%MatrixMarket matrix coordinate {type} {symmetry}\n");
             // Comments may be added here
             // Add Dimensions and non-zero count
-            MMString += $"{RowCount} {ColumnCount} {NonZeros}\n";
+            MMString.Append($"{RowCount} {ColumnCount} {NonZeros}\n");
             for (int i = 0; i < RowCount; i++)
             {
                 for (int j = 0; j < ColumnCount; j++)
                     if (this[i, j] != 0)
                     {
-                        MMString += $"{i} {j} {this[i, j]}\n";
-                    }
+                        MMString.Append($"{i} {j} {this[i, j]}\n");
                     }
-            return MMString;
             }
-
-        /// <summary>
-        /// Multiply this matrix with another matrix
-        /// </summary>
-        /// <param name="other">second matrix</param>
-        /// <returns>product matrix</returns>
-        public DoubleMatrix Multiply(DoubleMatrix other)
-        {
-            DoubleMatrix result = new DoubleMatrix(this.RowCount, other.ColumnCount);
-            for (int i = 0; i < this.RowCount; i++)
-            {
-                for (int j = 0; j < other.ColumnCount; j++)
-                {
-                    double s = 0;
-                    for (int k = 0; k < this.ColumnCount; k++)
-                    {
-                        s += this[i, k] * other[k, j];
-                    }
-                    result[i, j] = s;
-                }
-            }
-            return result;
+            return MMString.ToString();
         }
 
         /// <summary>

src/SparseTransform/DataStructures/IntegerMatrix.cs

+using System.Text;
+
 namespace SparseTransform.DataStructures
 {
     /// <summary>
@@ -41,7 +43,7 @@ namespace SparseTransform.DataStructures
         /// <returns>MatrixMarket String</returns>
         public String ToMatrixMarketString()
         {
-            String MMString;
+            StringBuilder MMString = new StringBuilder();
             String type = "integer";
             String symmetry;
             if (Symmetric)
@@ -53,44 +55,19 @@ namespace SparseTransform.DataStructures
                 symmetry = "general";
             }
             // Build header
-            MMString = $"%%MatrixMarket matrix coordinate {type} {symmetry}\n";
+            MMString.Append($"%%MatrixMarket matrix coordinate {type} {symmetry}\n");
             // Comments may be added here
             // Add Dimensions and non-zero count
-            MMString += $"{RowCount} {ColumnCount} {NonZeros}\n";
+            MMString.Append($"{RowCount} {ColumnCount} {NonZeros}\n");
             for (int i = 0; i < RowCount; i++)
             {
                 for (int j = 0; j < ColumnCount; j++)
-                {
                     if (this[i, j] != 0)
                     {
-                        MMString += $"{i} {j} {this[i, j]}\n";
-                    }
-                }
-            }
-            return MMString;
-        }
-
-        /// <summary>
-        /// Multiply this matrix with another matrix
-        /// </summary>
-        /// <param name="other">second matrix</param>
-        /// <returns>product matrix</returns>
-        public IntegerMatrix Multiply(IntegerMatrix other)
-        {
-            IntegerMatrix result = new IntegerMatrix(this.RowCount, other.ColumnCount);
-            for (int i = 0; i < this.RowCount; i++)
-            {
-                for (int j = 0; j < other.ColumnCount; j++)
-                {
-                    int s = 0;
-                    for (int k = 0; k < this.ColumnCount; k++)
-                    {
-                        s += this[i, k] * other[k, j];
-                    }
-                    result[i, j] = s;
+                        MMString.Append($"{i} {j} {this[i, j]}\n");
                     }
             }
-            return result;
+            return MMString.ToString();
         }
     }
 }
\ No newline at end of file