/*
 *  $Id: hindo.c,v 1.3 2001/06/14 18:15:55 ura Exp $
 */

/*
 * FreeWnn is a network-extensible Kana-to-Kanji conversion system.
 * This file is part of FreeWnn.
 * 
 * Copyright Kyoto University Research Institute for Mathematical Sciences
 *                 1987, 1988, 1989, 1990, 1991, 1992
 * Copyright OMRON Corporation. 1987, 1988, 1989, 1990, 1991, 1992, 1999
 * Copyright ASTEC, Inc. 1987, 1988, 1989, 1990, 1991, 1992
 * Copyright FreeWnn Project 1999, 2000
 *
 * Maintainer:  FreeWnn Project   <freewnn@tomo.gr.jp>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/*
                                                修正 9/1/89

        a＝実頻度, b＝仮頻度（共に非負整数）のとき

        b＝[a÷x]＋2(x−1) where x＝[( sqrt(1＋2a)＋1 )÷2]
        （計算結果が126を越えた場合は126とする。）

        (min)a＝(b−2y)(y＋1)         where y＝[b÷4]
        (mid)a＝(b−2y)(y＋1)＋[y÷2] where y＝[b÷4]
        （b≦126とする。）

        ここで[ ]はガウス記号
        bを与えてのaの推測値には幅があり、(min)aとはその最小値、
        (mid)aはその中間値
        b≦4 なら、(min)a＝(mid)a＝b

        仮頻度がbのとき、頻度の更新の確率は 1 / ([b÷4]＋1)
        但し b＝0の時は、頻度更新確率 0

    
         a == -1 <==> b == 0x7f = 127; 
        この時、このエントリーは、変換に決して用いられない
        (コメントアウトされている)ことを表す。
                        9/1/89 H.T.
*/

 /** 整数引数の平方根関数。但し引数<0の時のエラーチェックはなし（0を返す）。*/
static int
isqrt (i)
     int i;
{
  register int a, b;

  if (i <= 0)
    return (0);
  for (a = i, b = 1; b <<= 1, a >>= 2;);
  while ((a = i / b) < b)
    b = (b + a) >> 1;
  return (b);
}

 /** 実頻度a→仮頻度b */
int
asshuku (hin)
     int hin;
{
  register int c;

  if (hin == -1)
    return (127);
  if (hin <= 4)
    return (hin);
  /* 大半は頻度0と想定してのスピードアップ。motoni1,2でも同じ */

  c = (isqrt ((hin <<= 1) + 1) + 1) & ~1;
  c += hin / c - 2;
  return (c < 126 ? c : 126);
}

 /** 仮頻度b→実頻度(min)a */
/*
int
motoni1(hin)
int     hin;
{
        register int    c;

        if(hin == 127) return(-1);
        if(hin <= 4) return(hin); 
        c = hin >> 2;
        return( (hin - (c << 1)) * (c + 1) );
}
*/

 /** 仮頻度b→実頻度(mid)a */
int
motoni2 (hin)
     int hin;
{
  register int c;

  if (hin == 127)
    return (-1);
  if (hin <= 4)
    return (hin);
  c = hin >> 2;
  return ((hin - (c << 1)) * (c + 1) + (c >> 1));
}