Add Value Tuple based iteration to Matrix base class and DenseColumn and CompressedColumn storage mechanisms derived from that class. Use the value-based variant in the OfMatrix helper to avoid allocations.

Author: miniksa

CSparse/Matrix.cs

@@ -132,9 +132,18 @@ protected Matrix(int rowCount, int columnCount)
         /// <summary>
         /// Enumerates all values of the matrix.
         /// </summary>
+        /// <remarks>
+        /// <see cref="EnumerateIndexedAsValueTuples"/> for a version that returns stack-allocated value tuples to save transient heap allocations (saves performance overhead of allocations + garbage collection) of the <see cref="Tuple"/> class.
+        /// </remarks>
         /// <returns>Enumeration of tuples (i, j, a[i, j]).</returns>
         public abstract IEnumerable<Tuple<int, int, T>> EnumerateIndexed();
 
+        /// <summary>
+        /// Enumerates all values of the matrix, but returns as stack-allocated value tuples instead of heap-allocated tuples.
+        /// </summary>
+        /// <returns>Enumeration of tuples (i, j, a[i, j]).</returns>
+        public abstract IEnumerable<(int row, int column, T value)> EnumerateIndexedAsValueTuples();
+       
         /// <summary>
         /// Enumerates all values of the matrix.
         /// </summary>

CSparse/Storage/CompressedColumnStorage.cs

@@ -110,7 +110,7 @@ public CompressedColumnStorage(int rowCount, int columnCount, T[] values, int[]
         /// </summary>
         public static CompressedColumnStorage<T> OfMatrix(Matrix<T> matrix)
         {
-            var c = Converter.FromEnumerable<T>(matrix.EnumerateIndexed(), matrix.RowCount, matrix.ColumnCount);
+            var c = Converter.FromEnumerable<T>(matrix.EnumerateIndexedAsValueTuples(), matrix.RowCount, matrix.ColumnCount);
 
             return Converter.ToCompressedColumnStorage(c);
         }
@@ -580,6 +580,15 @@ public CompressedColumnStorage<T> Clone(bool values = true)
 
         /// <inheritdoc />
         public override IEnumerable<Tuple<int, int, T>> EnumerateIndexed()
+        {
+            foreach (var valueTuple in EnumerateIndexedAsValueTuples())
+            {
+                yield return Tuple.Create(valueTuple.row, valueTuple.column, valueTuple.value);
+            }
+        }
+
+        /// <inheritdoc />
+        public override IEnumerable<(int row, int column, T value)> EnumerateIndexedAsValueTuples()
         {
             var ax = Values;
             var ap = ColumnPointers;
@@ -590,7 +599,7 @@ public override IEnumerable<Tuple<int, int, T>> EnumerateIndexed()
                 var end = ap[i + 1];
                 for (var j = ap[i]; j < end; j++)
                 {
-                    yield return new Tuple<int, int, T>(ai[j], i, ax[j]);
+                    yield return (ai[j], i, ax[j]);
                 }
             }
         }

CSparse/Storage/DenseColumnMajorStorage.cs

@@ -165,8 +165,8 @@ public static DenseColumnMajorStorage<T> OfDiagonalArray(T[] diagonal)
         {
             int order = diagonal.Length;
 
-            var A = Create(order, order);
-            
+            var A = Create(order, order);
+
             for (int i = 0; i < order; i++)
             {
                 A.At(i, i, diagonal[i]);
@@ -547,12 +547,21 @@ public override void Clear()
 
         /// <inheritdoc />
         public override IEnumerable<Tuple<int, int, T>> EnumerateIndexed()
+        {
+            foreach (var valueTuple in EnumerateIndexedAsValueTuples())
+            {
+                yield return Tuple.Create(valueTuple.row, valueTuple.column, valueTuple.value);
+            }
+        }
+
+        /// <inheritdoc />
+        public override IEnumerable<(int row, int column, T value)> EnumerateIndexedAsValueTuples()
         {
             for (int row = 0; row < rows; row++)
             {
                 for (int column = 0; column < columns; column++)
                 {
-                    yield return new Tuple<int, int, T>(row, column, Values[(column * rows) + row]);
+                    yield return (row, column, Values[(column * rows) + row]);
                 }
             }
         }