fix for empty dense matrix

nalgebra-sparse/src/io/matrix_market.rs

@@ -1072,17 +1072,6 @@ fn parse_dense_shape(
     let mut inner = shape_inner.into_inner();
     let r = inner.next().unwrap().as_str().parse::<usize>().unwrap();
     let c = inner.next().unwrap().as_str().parse::<usize>().unwrap();
-    // shape information can't use 0 as dimension
-    if r * c == 0 {
-        return Err(MatrixMarketError::from_kind_and_message(
-            MatrixMarketErrorKind::ZeroError,
-            String::from(
-                "
-        Matrix can't have 0 as shape dimensions.
-        ",
-            ),
-        ));
-    }
 
     // check for square matrix, when it's not a general matrix
     if *storagescheme != StorageScheme::General && r != c {

nalgebra-sparse/tests/unit_tests/matrix_market.rs

@@ -7,7 +7,7 @@ use nalgebra_sparse::CooMatrix;
 #[test]
 #[rustfmt::skip]
 fn test_matrixmarket_sparse_real_general_empty() {
-    // Test several valid zero-shapes of a matrix
+    // Test several valid zero-shapes of a sparse matrix
     let shapes = vec![ (0, 0), (1, 0), (0, 1) ];
     let strings: Vec<String> = shapes
         .iter()
@@ -22,6 +22,24 @@ fn test_matrixmarket_sparse_real_general_empty() {
     }
 }
 
+#[test]
+#[rustfmt::skip]
+fn test_matrixmarket_dense_real_general_empty() {
+    // Test several valid zero-shapes of a dense matrix
+    let shapes = vec![ (0, 0), (1, 0), (0, 1) ];
+    let strings: Vec<String> = shapes
+        .iter()
+        .map(|(m, n)| format!("%%MatrixMarket matrix array real general\n {} {}", m, n))
+        .collect();
+
+    for (shape,string) in shapes.iter().zip(strings.iter()) {
+        let sparse_mat = load_coo_from_matrix_market_str::<f32>(string).unwrap();
+        assert_eq!(sparse_mat.nrows(), shape.0);
+        assert_eq!(sparse_mat.ncols(), shape.1);
+        assert_eq!(sparse_mat.nnz(), 0);
+    }
+}
+
 #[test]
 #[rustfmt::skip]
 fn test_matrixmarket_sparse_real_general() {