June 2018 Update

Task/Cholesky-decomposition/Ring/cholesky-decomposition.ring

@@ -0,0 +1,45 @@
+# Project : Cholesky decomposition
+# Date    : 2017/11/12
+# Author : Gal Zsolt (~ CalmoSoft ~)
+# Email   : <calmosoft@gmail.com>
+
+load "stdlib.ring"
+decimals(5)
+m1 = [[25, 15, -5],
+          [15, 18,  0],
+          [-5,  0, 11]]
+cholesky(m1)
+printarray(m1)
+see nl
+
+m2 = [[18, 22,  54,  42],
+          [22, 70,  86,  62],
+          [54, 86, 174, 134],
+          [42, 62, 134, 106]]
+cholesky(m2)
+printarray(m2)
+
+func cholesky(a)
+l = newlist(len(a), len(a))
+for i = 1 to len(a)
+     for j = 1 to i
+         s = 0
+         for k = 1 to j
+             s = s + l[i][k] * l[j][k]
+         next
+         if i = j
+            l[i][j] = sqrt(a[i][i] - s)
+         else
+            l[i][j] = (a[i][j] - s) / l[j][j]
+         ok
+    next
+next
+a = l
+
+func printarray(a)
+       for row = 1 to len(a)
+            for col = 1 to len(a)
+                 see "" + a[row][col] + "  "
+            next
+            see nl
+       next