feat:node-modules

node_modules/mathjs/lib/esm/function/algebra/sparse/csEtree.js

@@ -0,0 +1,71 @@
+// Copyright (c) 2006-2024, Timothy A. Davis, All Rights Reserved.
+// SPDX-License-Identifier: LGPL-2.1+
+// https://github.com/DrTimothyAldenDavis/SuiteSparse/tree/dev/CSparse/Source
+
+/**
+ * Computes the elimination tree of Matrix A (using triu(A)) or the
+ * elimination tree of A'A without forming A'A.
+ *
+ * @param {Matrix}  a               The A Matrix
+ * @param {boolean} ata             A value of true the function computes the etree of A'A
+ */
+export function csEtree(a, ata) {
+  // check inputs
+  if (!a) {
+    return null;
+  }
+  // a arrays
+  var aindex = a._index;
+  var aptr = a._ptr;
+  var asize = a._size;
+  // rows & columns
+  var m = asize[0];
+  var n = asize[1];
+
+  // allocate result
+  var parent = []; // (n)
+
+  // allocate workspace
+  var w = []; // (n + (ata ? m : 0))
+  var ancestor = 0; // first n entries in w
+  var prev = n; // last m entries (ata = true)
+
+  var i, inext;
+
+  // check we are calculating A'A
+  if (ata) {
+    // initialize workspace
+    for (i = 0; i < m; i++) {
+      w[prev + i] = -1;
+    }
+  }
+  // loop columns
+  for (var k = 0; k < n; k++) {
+    // node k has no parent yet
+    parent[k] = -1;
+    // nor does k have an ancestor
+    w[ancestor + k] = -1;
+    // values in column k
+    for (var p0 = aptr[k], p1 = aptr[k + 1], p = p0; p < p1; p++) {
+      // row
+      var r = aindex[p];
+      // node
+      i = ata ? w[prev + r] : r;
+      // traverse from i to k
+      for (; i !== -1 && i < k; i = inext) {
+        // inext = ancestor of i
+        inext = w[ancestor + i];
+        // path compression
+        w[ancestor + i] = k;
+        // check no anc., parent is k
+        if (inext === -1) {
+          parent[i] = k;
+        }
+      }
+      if (ata) {
+        w[prev + r] = k;
+      }
+    }
+  }
+  return parent;
+}