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Member "mapm_4.9.5a/mapm_lg4.c" (21 Feb 2010, 2796 Bytes) of package /linux/misc/old/mapm-4.9.5a.tar.gz:

    1 
    2 /* 
    3  *  M_APM  -  mapm_lg4.c
    4  *
    5  *  Copyright (C) 2003 - 2007   Michael C. Ring
    6  *
    7  *  Permission to use, copy, and distribute this software and its
    8  *  documentation for any purpose with or without fee is hereby granted,
    9  *  provided that the above copyright notice appear in all copies and
   10  *  that both that copyright notice and this permission notice appear
   11  *  in supporting documentation.
   12  *
   13  *  Permission to modify the software is granted. Permission to distribute
   14  *  the modified code is granted. Modifications are to be distributed by
   15  *  using the file 'license.txt' as a template to modify the file header.
   16  *  'license.txt' is available in the official MAPM distribution.
   17  *
   18  *  This software is provided "as is" without express or implied warranty.
   19  */
   20 
   21 /*
   22  *      $Id: mapm_lg4.c,v 1.3 2007/12/03 01:43:32 mike Exp $
   23  *
   24  *      This file contains the LOG_NEAR_1 function.
   25  *
   26  *      $Log: mapm_lg4.c,v $
   27  *      Revision 1.3  2007/12/03 01:43:32  mike
   28  *      Update license
   29  *
   30  *      Revision 1.2  2003/06/02 18:08:45  mike
   31  *      tweak decimal places and add comments
   32  *
   33  *      Revision 1.1  2003/06/02 17:27:26  mike
   34  *      Initial revision
   35  */
   36 
   37 #include "m_apm_lc.h"
   38 
   39 /****************************************************************************/
   40 /*
   41     calculate log (1 + x) with the following series:
   42 
   43               x
   44     y = -----      ( |y| < 1 )
   45         x + 2
   46 
   47 
   48             [ 1 + y ]                 y^3     y^5     y^7
   49     log [-------]  =  2 * [ y  +  ---  +  ---  +  ---  ... ] 
   50             [ 1 - y ]                  3       5       7 
   51 
   52 */
   53 void    M_log_near_1(M_APM rr, int places, M_APM xx)
   54 {
   55 M_APM   tmp0, tmp1, tmp2, tmpS, term;
   56 int tolerance, dplaces, local_precision;
   57 long    m1;
   58 
   59 tmp0 = M_get_stack_var();
   60 tmp1 = M_get_stack_var();
   61 tmp2 = M_get_stack_var();
   62 tmpS = M_get_stack_var();
   63 term = M_get_stack_var();
   64 
   65 tolerance = xx->m_apm_exponent - (places + 6);
   66 dplaces   = (places + 12) - xx->m_apm_exponent;
   67 
   68 m_apm_add(tmp0, xx, MM_Two);
   69 m_apm_divide(tmpS, (dplaces + 6), xx, tmp0);
   70 
   71 m_apm_copy(term, tmpS);
   72 m_apm_multiply(tmp0, tmpS, tmpS);
   73 m_apm_round(tmp2, (dplaces + 6), tmp0);
   74 
   75 m1 = 3L;
   76 
   77 while (TRUE)
   78   {
   79    m_apm_multiply(tmp0, term, tmp2);
   80 
   81    if ((tmp0->m_apm_exponent < tolerance) || (tmp0->m_apm_sign == 0))
   82      break;
   83 
   84    local_precision = dplaces + tmp0->m_apm_exponent;
   85 
   86    if (local_precision < 20)
   87      local_precision = 20;
   88 
   89    m_apm_set_long(tmp1, m1);
   90    m_apm_round(term, local_precision, tmp0);
   91    m_apm_divide(tmp0, local_precision, term, tmp1);
   92    m_apm_add(tmp1, tmpS, tmp0);
   93    m_apm_copy(tmpS, tmp1);
   94    m1 += 2;
   95   }
   96 
   97 m_apm_multiply(tmp0, MM_Two, tmpS);
   98 m_apm_round(rr, places, tmp0);
   99 
  100 M_restore_stack(5);                    /* restore the 5 locals we used here */
  101 }
  102 /****************************************************************************/