added from_coo method to csr matrix

Author: RomanShushakov

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "extended_matrix"
-version = "0.9.6"
+version = "0.9.7"
 authors = ["Roman Shushakov <roman.a.shushakov1@gmail.com>"]
 edition = "2024"
 description = "A matrix calculation module."

src/matrix/csr_matrix.rs

@@ -114,6 +114,67 @@ where
         CsrMatrix::create(n_rows, n_cols, values, col_index, row_ptr)
     }
 
+    pub fn from_coo(
+        n_rows: usize,
+        n_cols: usize,
+        triplets: &[(usize, usize, V)],
+    ) -> Result<Self, String> {
+        if n_rows == 0 || n_cols == 0 {
+            return Err("CsrMatrix::from_coo: empty shape".to_string());
+        }
+
+        // Copy + validate
+        let mut entries: Vec<(usize, usize, V)> = Vec::with_capacity(triplets.len());
+        for &(r, c, v) in triplets {
+            if r >= n_rows || c >= n_cols {
+                return Err(format!(
+                    "CsrMatrix::from_coo: index out of bounds: ({},{}) for {}x{}",
+                    r, c, n_rows, n_cols
+                ));
+            }
+            entries.push((r, c, v));
+        }
+
+        // Sort by (row, col)
+        entries.sort_by(|a, b| (a.0, a.1).cmp(&(b.0, b.1)));
+
+        // Compress duplicates
+        let mut cols: Vec<usize> = Vec::new();
+        let mut vals: Vec<V> = Vec::new();
+        let mut row_ptr = vec![0usize; n_rows + 1];
+
+        let mut last_rc: Option<(usize, usize)> = None;
+
+        for (r, c, v) in entries {
+            match last_rc {
+                Some((lr, lc)) if lr == r && lc == c => {
+                    // duplicate -> sum
+                    let last = vals.last_mut().unwrap();
+                    *last = *last + v;
+                }
+                _ => {
+                    cols.push(c);
+                    vals.push(v);
+                    row_ptr[r + 1] += 1; // count nnz in row r
+                    last_rc = Some((r, c));
+                }
+            }
+        }
+
+        // Prefix sum: counts -> row pointers
+        for i in 0..n_rows {
+            row_ptr[i + 1] += row_ptr[i];
+        }
+
+        Ok(CsrMatrix {
+            n_rows,
+            n_cols,
+            values: vals,
+            col_index: cols,
+            row_ptr,
+        })
+    }
+
     pub fn spmv(&self, x: &[V]) -> Result<Vec<V>, String> {
         if x.len() != self.n_cols {
             return Err(format!(

src/tests/matrix/test_csr_matrix.rs

@@ -2,14 +2,14 @@
 
 use crate::{BasicOperationsTrait, CsrMatrix, Position, SquareMatrix};
 
+const ABS_TOL: f64 = 1e-12;
+
 fn mat2x2(a11: f64, a12: f64, a21: f64, a22: f64) -> SquareMatrix<f64> {
     SquareMatrix::create(2, &[a11, a12, a21, a22])
 }
 
 #[test]
 fn test_csr_from_square_matrix_and_spmv() {
-    const ABS_TOL: f64 = 1e-12;
-
     // A = [[4, 0],
     //      [1, 3]]
     let a = mat2x2(4.0, 0.0, 1.0, 3.0);
@@ -23,3 +23,35 @@ fn test_csr_from_square_matrix_and_spmv() {
     assert!((y[0] - 4.0).abs() < ABS_TOL);
     assert!((y[1] - 7.0).abs() < ABS_TOL);
 }
+
+#[test]
+fn test_from_coo_basic_spmv() {
+    // A = [4 1 0;
+    //      1 3 1;
+    //      0 1 2]
+    let trip = vec![
+        (0, 0, 4.0f64),
+        (0, 1, 1.0),
+        (1, 0, 1.0),
+        (1, 1, 3.0),
+        (1, 2, 1.0),
+        (2, 1, 1.0),
+        (2, 2, 2.0),
+    ];
+
+    let csr = CsrMatrix::from_coo(3, 3, &trip).unwrap();
+    let y = csr.spmv(&[1.0, 2.0, 3.0]).unwrap();
+    assert!((y[0] - 6.0).abs() < ABS_TOL);
+    assert!((y[1] - 10.0).abs() < ABS_TOL);
+    assert!((y[2] - 8.0).abs() < ABS_TOL);
+}
+
+#[test]
+fn test_from_coo_sums_duplicates() {
+    // A(0,0) = 1 + 2 = 3, A(1,1)=4
+    let trip = vec![(0usize, 0usize, 1.0f64), (0, 0, 2.0), (1, 1, 4.0)];
+    let csr = CsrMatrix::from_coo(2, 2, &trip).unwrap();
+    let y = csr.spmv(&[1.0, 1.0]).unwrap();
+    assert!((y[0] - 3.0).abs() < ABS_TOL);
+    assert!((y[1] - 4.0).abs() < ABS_TOL);
+}