;;; -*-  Mode: Lisp; Package: Maxima; Syntax: Common-Lisp; Base: 10 -*- ;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;     The data in this file contains enhancements.                   ;;;;;
;;;                                                                    ;;;;;
;;;  Copyright (c) 1984,1987 by William Schelter,University of Texas   ;;;;;
;;;     All rights reserved                                            ;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;     (c) Copyright 1982 Massachusetts Institute of Technology         ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(in-package :maxima)

(macsyma-module mat)

;; this is the mat package

(declare-top (special *ech* *tri*
		      mul* *det*
		      xm* xn* ax))

;;these are arrays.
(defvar *row*)
(defvar *col*)
(defvar *colinv*)


(defun solcoef (m *c varl flag)
  (prog (cc answer leftover)
     (setq cc (cdr (ratrep* *c)))
     (if (or (atom (car cc))
	     (not (equal (cdar cc) '(1 1)))
	     (not (equal 1 (cdr cc))))
     ;; NOTE TO TRANSLATORS: NOT CLEAR WHAT IS "UNACCEPTABLE" HERE
	 (merror (intl:gettext "solve: unacceptable variable: ~M") *c))
     (setq answer (ratreduce (prodcoef (car cc) (car m)) (cdr m)))
     (if (not flag) (return answer))
     (setq leftover
	   (rdis (ratplus m (rattimes (ratminus answer) cc t))))
     (if (or (not (freeof *c leftover))
	     (dependsall (rdis answer) varl))
         (rat-error "`non-linear'"))
     (return answer)))

(defun formx (flag nam eql varl)
  (prog (b ax x ix j)
     (setq varlist varl)
     (mapc #'newvar eql)
     (and (not $algebraic)
	  (some #'algp varlist)
	  (setq $algebraic t))
     (setf (symbol-value nam) (make-array (list (1+ (setq xn* (length eql)))
						(1+ (setq xm* (1+ (length varl)))))))
     (setq nam (get-array-pointer nam))
     (setq ix 0)
     loop1
     (cond ((null eql) (return  varlist)))
     (setq ax (car eql))
     (setq eql (cdr eql))
     (incf ix)
     (setf (aref nam ix xm*) (const ax varl))
     (setq j 0)
     (setq b varl) (setq ax (cdr (ratrep* ax)))
     loop2
     (setq x (car b))
     (setq b (cdr b))
     (incf j)
     (setf (aref nam ix j) (solcoef ax x varl flag))
     (cond (b (go loop2)))
     (go loop1)))

(defun dependsall (exp l)
  (cond ((null l) nil)
	((or (not (freeof (car l) exp)) (dependsall exp (cdr l))) t)
	(t nil)))

(setq *det* nil *ech* nil *tri* nil)

(defun ptorat (ax m n)
  (prog (i j)
     (setq ax (get-array-pointer ax))
     (setq i (1+ m))
     (incf n)
     loop1
     (when (equal i 1) (return nil))
     (decf i)
     (setq j n)
     loop2
     (when (equal j 1) (go loop1))
     (decf j)
     (setf (aref ax i j) (cons (aref ax i j) 1))
     (go loop2)))

(defun meqhk (z)
  "If Z is of the form lhs = rhs, return the expression lhs - rhs.
  Otherwise, return Z unchanged."
  (if (and (not (atom z)) (eq (caar z) 'mequal))
      (simplus (list '(mplus) (cadr z) (list '(mtimes) -1 (caddr z))) 1 nil)
      z))

(defun const (e varl)
  (setq varl (mapcar #'(lambda(x) (caadr (ratrep* x))) varl))
  (setq e (cdr (ratrep* e)))
  (let ((zl (make-list (length varl) :initial-element 0)))
    (ratreduce (pctimes -1 (pcsubsty zl varl (car e)))
	       (pcsubsty zl varl (cdr e)))))

(defvar *mosesflag nil)

(defun make-param ()
  (let ((param (intern (format nil "~A~D" '$%r (incf $%rnum)))))
    (tuchus $%rnum_list param)
    param))

(defun ith (x n)
  (if (atom x) nil (nth (1- n) x)))

(defun polyize (ax r m mul)
  (declare (fixnum m))
  (do ((c 1 (1+ c)) (d))
      ((> c m) nil)
    (declare (fixnum c))
    (setq d (aref ax r c))
    (setq d (cond ((equal mul 1) (car d))
		  (t (ptimes (car d)
			     (pquotientchk mul (cdr d))))))
    (setf (aref ax r c) (if $sparse (cons d 1) d))))

;; TWO-STEP FRACTION-FREE GAUSSIAN ELIMINATION ROUTINE

(defun tfgeli (ax n m &aux ($sparse (and $sparse (or *det* *inv*))))
  ;;$sparse is also controlling whether polyize stores polys or ratforms
  (setq ax (get-array-pointer ax))
  (setq mul* 1)
  (do ((r 1 (1+ r)))
      ((> r n) (cond ((and $sparse *det*)(sprdet ax n))
		     ((and *inv* $sparse)(newinv ax n m))
		     (t (tfgeli1 ax n m))))
    (do ((c 1 (1+ c))
	 (d)
	 (mul 1))
	((> c m)
	 (and *det* (setq mul* (ptimes mul* mul)))
	 (polyize ax r m mul))
      (cond ((equal 1 (setq d (cdr (aref ax r c)))) nil)
	    (t (setq mul (ptimes mul (pquotient d (pgcd mul d)))))))))

;; The author of the following programs is Tadatoshi Minamikawa (TM).
;; This program is one-step fraction-free Gaussian elimination with
;; optimal pivoting.  DRB claims the hair in this program is not
;; necessary and that straightforward Gaussian elimination is sufficient,
;; for sake of future implementers.

;; To debug, delete the comments around PRINT and BREAK statements.

(declare-top (special permsign rank delta nrow nvar *n* *m* variableorder
		      dependentrows inconsistentrows))

(defun tfgeli1 (ax *n* *m*)
  (prog (delta variableorder inconsistentrows
	 dependentrows nrow nvar rank permsign result)
     (setq ax (get-array-pointer ax))
     (setq *col* (make-array (1+ *m*) :initial-element 0))
     (setq *row* (make-array (1+ *n*) :initial-element 0))
     (setq *colinv* (make-array (1+ *m*) :initial-element 0))
     ;; (PRINT 'ONESTEP-LIPSON-WITH-PIVOTING)
     (setq nrow *n*)
     (setq nvar (cond (*rank* *m*) (*det* *m*) (*inv* *n*) (*ech* *m*) (*tri* *m*) (t (1- *m*))))
     (do ((i 1 (1+ i)))
	 ((> i *n*))
       (setf (aref *row* i) i))
     (do ((i 1 (1+ i)))
	 ((> i *m*))
       (setf (aref *col* i) i) (setf (aref *colinv* i) i))
     (setq result
	   (cond (*rank* (forward t) rank)
		 (*det* (forward t)
			(cond ((= nrow *n*) (cond (permsign  (pminus delta))
						(t delta)))
			      (t 0)))
		 (*inv* (forward t) (backward) (recoverorder1))
		 (*ech* (forward nil) (recoverorder2))
		 (*tri* (forward nil) (recoverorder2))
		 (t (forward t) (cond ($backsubst (backward)))
		    (recoverorder2)
		    (list dependentrows inconsistentrows variableorder))))
     (return result)))

;;FORWARD ELIMINATION
;;IF THE SWITCH *CPIVOT IS NIL, IT AVOIDS THE COLUMN PIVOTING.
(defun forward (*cpivot)
  (setq delta 1)		  ;DELTA HOLDS THE CURRENT DETERMINANT
  (do ((k 1 (1+ k))
       (nvar nvar)   ;PROTECTS AGAINST TEMPORARAY RESETS DONE IN PIVOT
       (*m* *m*))
      ((or (> k nrow) (> k nvar)))
    (cond ((pivot ax k *cpivot) (return nil)))
    ;; PIVOT IS T IF THERE IS NO MORE NON-ZERO ROW LEFT. THEN GET OUT OF THE LOOP
    (do ((i (1+ k) (1+ i)))
	((> i nrow))
      (do ((j (1+ k) (1+ j)))
	  ((> j *m*))
	(setf (aref ax (aref *row* i) (aref *col* j))
	       (pquotient (pdifference (ptimes (aref ax (aref *row* k) (aref *col* k))
					       (aref ax (aref *row* i) (aref *col* j)))
				       (ptimes (aref ax (aref *row* i) (aref *col* k))
					       (aref ax (aref *row* k) (aref *col* j))))
			  delta))))
    (do ((i (1+ k) (1+ i)))
	((> i nrow))
      (setf (aref ax (aref *row* i) (aref *col* k)) 0))
    (setq delta (aref ax (aref *row* k) (aref *col* k))))
  ;; UNDOES COLUMN HACK IN PIVOT.
  (or *cpivot (do ((i 1 (1+ i))) ((> i *m*)) (setf (aref *col* i) i)))
  (setq rank (min nrow nvar)))

;; BACKWARD SUBSTITUTION
(defun backward ()
  (declare(special ax delta *m* rank))
  (do ((i (1- rank) (1- i)))
      ((< i 1))
    (do ((l (1+ rank) (1+ l)))
    ((> l *m*))
      (setf (aref ax (aref *row* i) (aref *col* l))
    (let ((mess1  (pdifference
             (ptimes (aref ax (aref *row* i) (aref *col* l))
                 (aref ax (aref *row* rank) (aref *col* rank)))
             (do ((j (1+ i) (1+ j)) (sum 0))
                 ((> j rank) sum)
               (setq sum (pplus sum (ptimes (aref ax (aref *row* i) (aref *col* j))
                            (aref ax (aref *row* j) (aref *col* l))))))) )
          (mess2 (aref ax (aref *row* i) (aref *col* i))  ))
      (cond ((equal 0 mess1) 0)
        ((equal 0 mess2) 0)
        (t   ;;   (pquotient mess1 mess2) ; fixed by line below. RJF 1/12/2017

         (car (ratreduce mess1 mess2))
         )
        ))))
    (do ((l (1+ i) (1+ l)))
    ((> l rank))
      (setf (aref ax (aref *row* i) (aref *col* l)) 0)))
  ;; PUT DELTA INTO THE DIAGONAL MATRIX
  (setq delta (aref ax (aref *row* rank) (aref *col* rank)))
  (do ((i 1 (1+ i)))
      ((> i rank))
    (setf (aref ax (aref *row* i) (aref *col* i)) delta))  )

;;RECOVER THE ORDER OF ROWS AND COLUMNS.

(defun recoverorder1 ()
  ;;(PRINT 'REARRANGE)
  (do ((i nvar (1- i)))
      ((= i 0))
    (setq variableorder (cons i variableorder)))
  (do ((i (1+ rank) (1+ i)))
      ((> i *n*))
    (cond ((equal (aref ax (aref *row* i) (aref *col* *m*)) 0)
	   (setq dependentrows (cons (aref *row* i) dependentrows)))
	  (t (setq inconsistentrows (cons (aref *row* i) inconsistentrows)))))
  (do ((i 1 (1+ i)))
      ((> i *n*))
    (cond ((not (= (aref *row* (aref *colinv* i)) i))
	   (prog (k l)
	      (moverow ax *n* *m* i 0)
	      (setq l i)
	      loop
	      (setq k (aref *row* (aref *colinv* l)))
	      (setf (aref *row* (aref *colinv* l)) l)
	      (cond ((= k i) (moverow ax *n* *m* 0 l))
		    (t (moverow ax *n* *m* k l)
		       (setq l k)
		       (go loop))))))))

(defun recoverorder2 ()
  (do ((i nvar (1- i)))
      ((= i 0))
    (setq variableorder (cons (aref *col* i) variableorder)))
  (do ((i (1+ rank) (1+ i)))
      ((> i *n*))
    (cond ((equal (aref ax (aref *row* i) (aref *col* *m*)) 0)
	   (setq dependentrows (cons (aref *row* i) dependentrows)))
	  (t (setq inconsistentrows (cons (aref *row* i) inconsistentrows)))))
  (do ((i 1 (1+ i)))
      ((> i *n*))
    (cond ((not (= (aref *row* i) i))
	   (prog (k l)
	      (moverow ax *n* *m* i 0)
	      (setq l i)
	      loop
	      (setq k (aref *row* l))
	      (setf (aref *row* l) l)
	      (cond ((= k i) (moverow ax *n* *m* 0 l))
		    (t (moverow ax *n* *m* k l)
		       (setq l k)
		       (go loop)))))))
  (do ((i 1 (1+ i)))
      ((> i nvar))
    (cond ((not (= (aref *col* i) i))
	   (prog (k l)
	      (movecol ax *n* *m* i 0)
	      (setq l i)
	      loop2
	      (setq k (aref *col* l))
	      (setf (aref *col* l) l)
	      (cond ((= k i) (movecol ax *n* *m* 0 l))
		    (t (movecol ax *n* *m* k l)
		       (setq l k)
		       (go loop2))))))))

;;THIS PROGRAM IS USED IN REARRANGEMENT
(defun moverow (ax *n* *m* i j)
  (do ((k 1 (1+ k))) ((> k *m*))
    (setf (aref ax j k) (aref ax i k))))

(defun movecol (ax *n* *m* i j)
  (do ((k 1 (1+ k))) ((> k *n*))
    (setf (aref ax k j) (aref ax k i))))

;;COMPLEXITY IS DEFINED AS FOLLOWS
;; COMPLEXITY(0)=0
;; COMPLEXITY(CONSTANT)=1
;; COMPLEXITY(POLYNOMIAL)=1+SUM(COMPLEXITY(C(N))+COMPLEXITY(E(N)), FOR N=0,1 ...M)
;; WHERE POLYNOMIAL IS OF THE FORM
;;    SUM(C(N)*X^E(N), FOR N=0,1 ... M)     X IS THE VARIABLE

(defun complexity (exp)
  (cond ((null exp) 0)
	((equal exp 0) 0)
	((atom  exp) 1)
	(t (+ (complexity (car exp)) (complexity (cdr exp))))))

(defun complexity/row (ax i j1 j2)
  (do ((j j1 (1+ j)) (sum 0))
      ((> j j2) sum)
    (incf sum (complexity (aref ax (aref *row* i) (aref *col* j))))))

(defun complexity/col (ax j i1 i2)
  (do ((i i1 (1+ i)) (sum 0))
      ((> i i2) sum)
    (incf sum (complexity (aref ax (aref *row* i) (aref *col* j))))))

(defun zerop/row (ax i j1 j2)
  (do ((j j1 (1+ j)))
      ((> j j2) t)
    (cond ((not (equal (aref ax (aref *row* i) (aref *col* j)) 0)) (return nil)))))

;;PIVOTING ALGORITHM
(defun pivot (ax k *cpivot)
  (prog (row/optimal col/optimal complexity/i/min complexity/j/min
	 complexity/i complexity/j complexity/det complexity/det/min dummy)
     (setq row/optimal k complexity/i/min 1000000. complexity/j/min 1000000.)
     ;;TEST THE SINGULARITY
     (cond ((do ((i k (1+ i)) (isallzero t))
		((> i nrow) isallzero)
	     loop (cond ((zerop/row ax i k nvar)
			 (cond (*inv* (merror (intl:gettext "solve: singular matrix.")))
			       (t (exchangerow i nrow)
				  (decf nrow)))
			 (unless (> i nrow) (go loop)))
			(t (setq isallzero nil))))
	    (return t)))

     ;; FIND AN OPTIMAL ROW
     ;; IF *CPIVOT IS NIL, (AX I K) WHICH IS TO BE THE PIVOT MUST BE NONZERO.
     ;; BUT IF *CPIVOT IS T, IT IS UNNECESSARY BECAUSE WE CAN DO THE COLUMN PIVOT.
     findrow
     (do ((i k (1+ i)))
	 ((> i nrow))
       (cond ((or *cpivot (not (equal (aref ax (aref *row* i) (aref *col* k)) 0)))
	      (cond ((> complexity/i/min
			(setq complexity/i (complexity/row ax i k *m*)))
		     (setq row/optimal i complexity/i/min complexity/i))))))
     ;; EXCHANGE THE ROWS K AND ROW/OPTIMAL
     (exchangerow k row/optimal)

     ;; IF THE FLAG *CPIVOT IS NIL, THE FOLLOWING STEPS ARE NOT EXECUTED.
     ;; THIS TREATMENT WAS DONE FOR THE LSA AND ECHELONTHINGS WHICH ARE NOT
     ;; HAPPY WITH THE COLUMN OPERATIONS.
     (cond ((null *cpivot)
	    (cond ((not (equal (aref ax (aref *row* k) (aref *col* k)) 0))
		   (return nil))
		  (t (do ((i k (1+ i))) ((= i nvar))
		       (setf (aref *col* i) (aref *col* (1+ i))))
		     (setq nvar (1- nvar) *m* (1- *m*))
		     (go findrow)))))

     ;;STEP3 ... FIND THE OPTIMAL COLUMN
     (setq col/optimal 0
	   complexity/det/min 1000000.
	   complexity/j/min 1000000.)

     (do ((j k (1+ j)))
	 ((> j nvar))
       (cond ((not (equal (aref ax (aref *row* k) (aref *col* j)) 0))
	      (cond ((> complexity/det/min
			(setq complexity/det
			      (complexity (aref ax (aref *row* k) (aref *col* j)))))
		     (setq col/optimal j
			   complexity/det/min complexity/det
			   complexity/j/min (complexity/col ax j (1+ k) *n*)))
		    ((equal complexity/det/min complexity/det)
		     (cond ((> complexity/j/min
			       (setq complexity/j
				     (complexity/col ax j (1+ k) *n*)))
			    (setq col/optimal j
				  complexity/det/min complexity/det
				  complexity/j/min complexity/j))))))))

     ;; EXCHANGE THE COLUMNS K AND COL/OPTIMAL
     (exchangecol  k col/optimal)
     (setq dummy (aref *colinv* (aref *col* k)))
     (setf (aref *colinv* (aref *col* k)) (aref *colinv* (aref *col* col/optimal)))
     (setf (aref *colinv* (aref *col* col/optimal)) dummy)
     (return nil)))

(defun exchangerow (i j)
  (prog (dummy)
     (setq dummy (aref *row* i))
     (setf (aref *row* i) (aref *row* j))
     (setf (aref *row* j) dummy)
     (cond ((= i j) (return nil))
	   (t (setq permsign (not permsign))))))

(defun exchangecol (i j)
  (prog (dummy)
     (setq dummy (aref *col* i))
     (setf (aref *col* i) (aref *col* j))
     (setf (aref *col* j) dummy)
     (cond ((= i j) (return nil))
	   (t (setq permsign (not permsign))))))

;; Displays list of solutions.

(defun solve2 (llist equations)
  (setq $multiplicities nil)
  (map2c #'(lambda (equatn multipl)
	     (setq equations
		   (nconc equations (list (displine equatn))))
	     (push multipl $multiplicities)
	     (if (and (> multipl 1) $dispflag)
		 (mtell (intl:gettext "solve: multiplicity ~A~%") multipl)))
	 llist)
  (values (setq $multiplicities (cons '(mlist simp) (nreverse $multiplicities)))
	  equations))

;; Displays an expression and returns its linelabel.

(defun displine (exp)
  (let ($nolabels (tim 0))
    (elabel exp)
    (cond ($dispflag (remprop *linelabel* 'nodisp)
		     (setq tim (get-internal-run-time))
		     (mterpri)
		     (displa (list '(mlabel) *linelabel* exp))
		     (timeorg tim))
	  (t (putprop *linelabel* t 'nodisp)))
    *linelabel*))

(declare-top (unspecial permsign rank delta nrow nvar *n* *m* variableorder
			dependentrows inconsistentrows))
