mirrors/emacs
1
Fork 0
mirror of git://git.sv.gnu.org/emacs.git synced 2025-12-15 10:30:25 -08:00
Code Issues Projects Releases Wiki Activity

* calc/calc-mtx.el (math-lud-pivot-check): New function.

Browse source 
(math-do-matrix-lud): Use `math-lud-pivot-check' to check the size
of potential pivots.
This commit is contained in:
Jay Belanger 2011-01-31 20:15:52 -06:00
parent 14beddf471
commit 4fdfcddf73
2 changed files with 21 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

16
lisp/calc/calc-mtx.el
View file

@ -232,6 +232,20 @@
(setq math-lud-cache (cons (cons m entry) math-lud-cache)))
lud))))
(defun math-lud-pivot-check (a)
"Determine a useful value for checking the size of potential pivots
in LUD decomposition."
(cond ((eq (car-safe a) 'mod)
(if (and (math-integerp (nth 1 a))
(math-integerp (nth 2 a))
(eq (math-gcd (nth 1 a) (nth 2 a)) 1))
1
0))
(t
(math-abs-approx a))))
;;; Numerical Recipes section 2.3; implicit pivoting omitted.
(defun math-do-matrix-lud (m)
(let* ((lu (math-copy-matrix m))
@ -261,7 +275,7 @@
(nth j (nth k lu))))
k (1+ k)))
(setcar (nthcdr j (nth i lu)) sum)
(let ((dum (math-abs-approx sum)))
(let ((dum (math-lud-pivot-check sum)))
(if (Math-lessp big dum)
(setq big dum
imax i)))