Function: math-lud-solve

math-lud-solve is an autoloaded and byte-compiled function defined in calc-mtx.el.gz.

Signature

(math-lud-solve LUD B &optional NEED)

Source Code

;; Defined in /usr/src/emacs/lisp/calc/calc-mtx.el.gz
(defun math-lud-solve (lud b &optional need)
  (if lud
      (let* ((x (math-copy-matrix b))
	     (n (1- (length x)))
	     (m (1- (length (nth 1 x))))
	     (lu (car lud))
	     (col 1)
	     i j ip ii index sum)
	(while (<= col m)
	  (math-working "LUD solver step" col)
	  (setq i 1
		ii nil
		index (nth 1 lud))
	  (while (<= i n)
	    (setq ip (car index)
		  index (cdr index)
		  sum (nth col (nth ip x)))
	    (setcar (nthcdr col (nth ip x)) (nth col (nth i x)))
	    (if (null ii)
		(or (math-zerop sum)
		    (setq ii i))
	      (setq j ii)
	      (while (< j i)
		(setq sum (math-sub sum (math-mul (nth j (nth i lu))
						  (nth col (nth j x))))
		      j (1+ j))))
	    (setcar (nthcdr col (nth i x)) sum)
	    (setq i (1+ i)))
	  (while (>= (setq i (1- i)) 1)
	    (setq sum (nth col (nth i x))
		  j i)
	    (while (<= (setq j (1+ j)) n)
	      (setq sum (math-sub sum (math-mul (nth j (nth i lu))
						(nth col (nth j x))))))
	    (setcar (nthcdr col (nth i x))
		    (math-div sum (nth i (nth i lu)))))
	  (setq col (1+ col)))
	x)
    (and need
	 (math-reject-arg need "*Singular matrix"))))