Return to sqrt.c CVS log

Up to [ELWIX - Embedded LightWeight unIX -] / embedaddon / php / ext / bcmath / libbcmath / src

Annotation of embedaddon/php/ext/bcmath/libbcmath/src/sqrt.c, revision 1.1

1.1     ! misho       1: /* sqrt.c: bcmath library file. */
        !             2: /*
        !             3:     Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc.
        !             4:     Copyright (C) 2000 Philip A. Nelson
        !             5: 
        !             6:     This library is free software; you can redistribute it and/or
        !             7:     modify it under the terms of the GNU Lesser General Public
        !             8:     License as published by the Free Software Foundation; either
        !             9:     version 2 of the License, or (at your option) any later version.
        !            10: 
        !            11:     This library is distributed in the hope that it will be useful,
        !            12:     but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            13:     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
        !            14:     Lesser General Public License for more details.  (COPYING.LIB)
        !            15: 
        !            16:     You should have received a copy of the GNU Lesser General Public
        !            17:     License along with this library; if not, write to:
        !            18: 
        !            19:       The Free Software Foundation, Inc.
        !            20:       59 Temple Place, Suite 330
        !            21:       Boston, MA 02111-1307 USA.
        !            22: 
        !            23:     You may contact the author by:
        !            24:        e-mail:  philnelson@acm.org
        !            25:       us-mail:  Philip A. Nelson
        !            26:                 Computer Science Department, 9062
        !            27:                 Western Washington University
        !            28:                 Bellingham, WA 98226-9062
        !            29:        
        !            30: *************************************************************************/
        !            31: 
        !            32: #include <config.h>
        !            33: #include <stdio.h>
        !            34: #include <assert.h>
        !            35: #include <stdlib.h>
        !            36: #include <ctype.h>
        !            37: #include <stdarg.h>
        !            38: #include "bcmath.h"
        !            39: #include "private.h"
        !            40: 
        !            41: /* Take the square root NUM and return it in NUM with SCALE digits
        !            42:    after the decimal place. */
        !            43: 
        !            44: int
        !            45: bc_sqrt (bc_num *num, int scale TSRMLS_DC)
        !            46: {
        !            47:   int rscale, cmp_res, done;
        !            48:   int cscale;
        !            49:   bc_num guess, guess1, point5, diff;
        !            50: 
        !            51:   /* Initial checks. */
        !            52:   cmp_res = bc_compare (*num, BCG(_zero_));
        !            53:   if (cmp_res < 0)
        !            54:     return 0;          /* error */
        !            55:   else
        !            56:     {
        !            57:       if (cmp_res == 0)
        !            58:        {
        !            59:          bc_free_num (num);
        !            60:          *num = bc_copy_num (BCG(_zero_));
        !            61:          return 1;
        !            62:        }
        !            63:     }
        !            64:   cmp_res = bc_compare (*num, BCG(_one_));
        !            65:   if (cmp_res == 0)
        !            66:     {
        !            67:       bc_free_num (num);
        !            68:       *num = bc_copy_num (BCG(_one_));
        !            69:       return 1;
        !            70:     }
        !            71: 
        !            72:   /* Initialize the variables. */
        !            73:   rscale = MAX (scale, (*num)->n_scale);
        !            74:   bc_init_num(&guess TSRMLS_CC);
        !            75:   bc_init_num(&guess1 TSRMLS_CC);
        !            76:   bc_init_num(&diff TSRMLS_CC);
        !            77:   point5 = bc_new_num (1,1);
        !            78:   point5->n_value[1] = 5;
        !            79: 
        !            80: 
        !            81:   /* Calculate the initial guess. */
        !            82:   if (cmp_res < 0)
        !            83:     {
        !            84:       /* The number is between 0 and 1.  Guess should start at 1. */
        !            85:       guess = bc_copy_num (BCG(_one_));
        !            86:       cscale = (*num)->n_scale;
        !            87:     }
        !            88:   else
        !            89:     {
        !            90:       /* The number is greater than 1.  Guess should start at 10^(exp/2). */
        !            91:       bc_int2num (&guess,10);
        !            92: 
        !            93:       bc_int2num (&guess1,(*num)->n_len);
        !            94:       bc_multiply (guess1, point5, &guess1, 0 TSRMLS_CC);
        !            95:       guess1->n_scale = 0;
        !            96:       bc_raise (guess, guess1, &guess, 0 TSRMLS_CC);
        !            97:       bc_free_num (&guess1);
        !            98:       cscale = 3;
        !            99:     }
        !           100: 
        !           101:   /* Find the square root using Newton's algorithm. */
        !           102:   done = FALSE;
        !           103:   while (!done)
        !           104:     {
        !           105:       bc_free_num (&guess1);
        !           106:       guess1 = bc_copy_num (guess);
        !           107:       bc_divide (*num, guess, &guess, cscale TSRMLS_CC);
        !           108:       bc_add (guess, guess1, &guess, 0);
        !           109:       bc_multiply (guess, point5, &guess, cscale TSRMLS_CC);
        !           110:       bc_sub (guess, guess1, &diff, cscale+1);
        !           111:       if (bc_is_near_zero (diff, cscale))
        !           112:        {
        !           113:          if (cscale < rscale+1)
        !           114:            cscale = MIN (cscale*3, rscale+1);
        !           115:          else
        !           116:            done = TRUE;
        !           117:        }
        !           118:     }
        !           119: 
        !           120:   /* Assign the number and clean up. */
        !           121:   bc_free_num (num);
        !           122:   bc_divide (guess,BCG(_one_),num,rscale TSRMLS_CC);
        !           123:   bc_free_num (&guess);
        !           124:   bc_free_num (&guess1);
        !           125:   bc_free_num (&point5);
        !           126:   bc_free_num (&diff);
        !           127:   return 1;
        !           128: }
        !           129: