Check for floating point in SVD diagonal

If the diagonal has duplicate eigenvalues that are floats, the sort operation can shuffle them around. The strict equivalence then fails when it technically should not.

Instead, we can compare the diagonal entries to the sorted entries using `AlmostEqual` with the matrix error for tolerance.

Author: Aweptimum

src/LinearAlgebra/Decomposition/SVD.php

@@ -344,7 +344,15 @@ private static function isDiagonalDescending(NumericMatrix $S): bool
         $diagonal = $S->getDiagonalElements();
         $sorted = array_values($diagonal); rsort($sorted, SORT_NUMERIC);
 
-        return $diagonal === $sorted;
+        // Compare sorted using matrix error (in case duplicate, floating-point eigenvalues) 
+        $n = count($diagonal);
+        for ($i = 0; $i < $n; $i++) {
+            if (!Arithmetic::almostEqual($diagonal[$i], $sorted[$i], $S->getError())) {
+                return false;
+            }
+        }
+
+        return true;
     }
 
     /**