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<h1>src/libsphinxbase/fe/fixlog.c</h1> </div>
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<div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/* -*- c-basic-offset: 4; indent-tabs-mode: nil -*- */</span>
<a name="l00002"></a>00002 <span class="comment">/* ====================================================================</span>
<a name="l00003"></a>00003 <span class="comment"> * Copyright (c) 2005 Carnegie Mellon University. All rights </span>
<a name="l00004"></a>00004 <span class="comment"> * reserved.</span>
<a name="l00005"></a>00005 <span class="comment"> *</span>
<a name="l00006"></a>00006 <span class="comment"> * Redistribution and use in source and binary forms, with or without</span>
<a name="l00007"></a>00007 <span class="comment"> * modification, are permitted provided that the following conditions</span>
<a name="l00008"></a>00008 <span class="comment"> * are met:</span>
<a name="l00009"></a>00009 <span class="comment"> *</span>
<a name="l00010"></a>00010 <span class="comment"> * 1. Redistributions of source code must retain the above copyright</span>
<a name="l00011"></a>00011 <span class="comment"> * notice, this list of conditions and the following disclaimer. </span>
<a name="l00012"></a>00012 <span class="comment"> *</span>
<a name="l00013"></a>00013 <span class="comment"> * 2. Redistributions in binary form must reproduce the above copyright</span>
<a name="l00014"></a>00014 <span class="comment"> * notice, this list of conditions and the following disclaimer in</span>
<a name="l00015"></a>00015 <span class="comment"> * the documentation and/or other materials provided with the</span>
<a name="l00016"></a>00016 <span class="comment"> * distribution.</span>
<a name="l00017"></a>00017 <span class="comment"> *</span>
<a name="l00018"></a>00018 <span class="comment"> * This work was supported in part by funding from the Defense Advanced </span>
<a name="l00019"></a>00019 <span class="comment"> * Research Projects Agency and the National Science Foundation of the </span>
<a name="l00020"></a>00020 <span class="comment"> * United States of America, and the CMU Sphinx Speech Consortium.</span>
<a name="l00021"></a>00021 <span class="comment"> *</span>
<a name="l00022"></a>00022 <span class="comment"> * THIS SOFTWARE IS PROVIDED BY CARNEGIE MELLON UNIVERSITY ``AS IS'' AND </span>
<a name="l00023"></a>00023 <span class="comment"> * ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, </span>
<a name="l00024"></a>00024 <span class="comment"> * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR</span>
<a name="l00025"></a>00025 <span class="comment"> * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY</span>
<a name="l00026"></a>00026 <span class="comment"> * NOR ITS EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,</span>
<a name="l00027"></a>00027 <span class="comment"> * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT </span>
<a name="l00028"></a>00028 <span class="comment"> * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, </span>
<a name="l00029"></a>00029 <span class="comment"> * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY </span>
<a name="l00030"></a>00030 <span class="comment"> * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT </span>
<a name="l00031"></a>00031 <span class="comment"> * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE </span>
<a name="l00032"></a>00032 <span class="comment"> * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.</span>
<a name="l00033"></a>00033 <span class="comment"> *</span>
<a name="l00034"></a>00034 <span class="comment"> * ====================================================================</span>
<a name="l00035"></a>00035 <span class="comment"> *</span>
<a name="l00036"></a>00036 <span class="comment"> * File: fixlog.c</span>
<a name="l00037"></a>00037 <span class="comment"> *</span>
<a name="l00038"></a>00038 <span class="comment"> * Description: Fast approximate fixed-point logarithms</span>
<a name="l00039"></a>00039 <span class="comment"> *</span>
<a name="l00040"></a>00040 <span class="comment"> * Author: David Huggins-Daines <dhuggins@cs.cmu.edu></span>
<a name="l00041"></a>00041 <span class="comment"> *</span>
<a name="l00042"></a>00042 <span class="comment"> */</span>
<a name="l00043"></a>00043
<a name="l00044"></a>00044 <span class="preprocessor">#ifdef HAVE_CONFIG_H</span>
<a name="l00045"></a>00045 <span class="preprocessor"></span><span class="preprocessor">#include <config.h></span>
<a name="l00046"></a>00046 <span class="preprocessor">#endif</span>
<a name="l00047"></a>00047 <span class="preprocessor"></span>
<a name="l00048"></a>00048 <span class="preprocessor">#include "sphinxbase/prim_type.h"</span>
<a name="l00049"></a>00049 <span class="preprocessor">#include "sphinxbase/fixpoint.h"</span>
<a name="l00050"></a>00050
<a name="l00051"></a>00051 <span class="preprocessor">#include "fe_internal.h"</span>
<a name="l00052"></a>00052
<a name="l00053"></a>00053 <span class="comment">/* Table of log2(x/64)*(1<<DEFAULT_RADIX) */</span>
<a name="l00054"></a>00054 <span class="comment">/* perl -e 'for (0..63) {my $x = 1 + $_/64; print "\t(uint32)(", log($x)/log(2), "*(1<<DEFAULT_RADIX)),\n"}' */</span>
<a name="l00055"></a>00055 <span class="keyword">static</span> uint32 logtable[] = {
<a name="l00056"></a>00056 (uint32) (0 * (1 << DEFAULT_RADIX)),
<a name="l00057"></a>00057 (uint32) (0.0223678130284545 * (1 << DEFAULT_RADIX)),
<a name="l00058"></a>00058 (uint32) (0.0443941193584534 * (1 << DEFAULT_RADIX)),
<a name="l00059"></a>00059 (uint32) (0.0660891904577724 * (1 << DEFAULT_RADIX)),
<a name="l00060"></a>00060 (uint32) (0.0874628412503394 * (1 << DEFAULT_RADIX)),
<a name="l00061"></a>00061 (uint32) (0.108524456778169 * (1 << DEFAULT_RADIX)),
<a name="l00062"></a>00062 (uint32) (0.129283016944966 * (1 << DEFAULT_RADIX)),
<a name="l00063"></a>00063 (uint32) (0.149747119504682 * (1 << DEFAULT_RADIX)),
<a name="l00064"></a>00064 (uint32) (0.169925001442312 * (1 << DEFAULT_RADIX)),
<a name="l00065"></a>00065 (uint32) (0.189824558880017 * (1 << DEFAULT_RADIX)),
<a name="l00066"></a>00066 (uint32) (0.20945336562895 * (1 << DEFAULT_RADIX)),
<a name="l00067"></a>00067 (uint32) (0.228818690495881 * (1 << DEFAULT_RADIX)),
<a name="l00068"></a>00068 (uint32) (0.247927513443586 * (1 << DEFAULT_RADIX)),
<a name="l00069"></a>00069 (uint32) (0.266786540694901 * (1 << DEFAULT_RADIX)),
<a name="l00070"></a>00070 (uint32) (0.285402218862248 * (1 << DEFAULT_RADIX)),
<a name="l00071"></a>00071 (uint32) (0.303780748177103 * (1 << DEFAULT_RADIX)),
<a name="l00072"></a>00072 (uint32) (0.321928094887362 * (1 << DEFAULT_RADIX)),
<a name="l00073"></a>00073 (uint32) (0.339850002884625 * (1 << DEFAULT_RADIX)),
<a name="l00074"></a>00074 (uint32) (0.357552004618084 * (1 << DEFAULT_RADIX)),
<a name="l00075"></a>00075 (uint32) (0.375039431346925 * (1 << DEFAULT_RADIX)),
<a name="l00076"></a>00076 (uint32) (0.39231742277876 * (1 << DEFAULT_RADIX)),
<a name="l00077"></a>00077 (uint32) (0.409390936137702 * (1 << DEFAULT_RADIX)),
<a name="l00078"></a>00078 (uint32) (0.426264754702098 * (1 << DEFAULT_RADIX)),
<a name="l00079"></a>00079 (uint32) (0.442943495848728 * (1 << DEFAULT_RADIX)),
<a name="l00080"></a>00080 (uint32) (0.459431618637297 * (1 << DEFAULT_RADIX)),
<a name="l00081"></a>00081 (uint32) (0.475733430966398 * (1 << DEFAULT_RADIX)),
<a name="l00082"></a>00082 (uint32) (0.491853096329675 * (1 << DEFAULT_RADIX)),
<a name="l00083"></a>00083 (uint32) (0.507794640198696 * (1 << DEFAULT_RADIX)),
<a name="l00084"></a>00084 (uint32) (0.523561956057013 * (1 << DEFAULT_RADIX)),
<a name="l00085"></a>00085 (uint32) (0.539158811108031 * (1 << DEFAULT_RADIX)),
<a name="l00086"></a>00086 (uint32) (0.554588851677637 * (1 << DEFAULT_RADIX)),
<a name="l00087"></a>00087 (uint32) (0.569855608330948 * (1 << DEFAULT_RADIX)),
<a name="l00088"></a>00088 (uint32) (0.584962500721156 * (1 << DEFAULT_RADIX)),
<a name="l00089"></a>00089 (uint32) (0.599912842187128 * (1 << DEFAULT_RADIX)),
<a name="l00090"></a>00090 (uint32) (0.614709844115208 * (1 << DEFAULT_RADIX)),
<a name="l00091"></a>00091 (uint32) (0.62935662007961 * (1 << DEFAULT_RADIX)),
<a name="l00092"></a>00092 (uint32) (0.643856189774725 * (1 << DEFAULT_RADIX)),
<a name="l00093"></a>00093 (uint32) (0.658211482751795 * (1 << DEFAULT_RADIX)),
<a name="l00094"></a>00094 (uint32) (0.672425341971496 * (1 << DEFAULT_RADIX)),
<a name="l00095"></a>00095 (uint32) (0.686500527183218 * (1 << DEFAULT_RADIX)),
<a name="l00096"></a>00096 (uint32) (0.700439718141092 * (1 << DEFAULT_RADIX)),
<a name="l00097"></a>00097 (uint32) (0.714245517666123 * (1 << DEFAULT_RADIX)),
<a name="l00098"></a>00098 (uint32) (0.727920454563199 * (1 << DEFAULT_RADIX)),
<a name="l00099"></a>00099 (uint32) (0.741466986401147 * (1 << DEFAULT_RADIX)),
<a name="l00100"></a>00100 (uint32) (0.754887502163469 * (1 << DEFAULT_RADIX)),
<a name="l00101"></a>00101 (uint32) (0.768184324776926 * (1 << DEFAULT_RADIX)),
<a name="l00102"></a>00102 (uint32) (0.78135971352466 * (1 << DEFAULT_RADIX)),
<a name="l00103"></a>00103 (uint32) (0.794415866350106 * (1 << DEFAULT_RADIX)),
<a name="l00104"></a>00104 (uint32) (0.807354922057604 * (1 << DEFAULT_RADIX)),
<a name="l00105"></a>00105 (uint32) (0.820178962415188 * (1 << DEFAULT_RADIX)),
<a name="l00106"></a>00106 (uint32) (0.832890014164742 * (1 << DEFAULT_RADIX)),
<a name="l00107"></a>00107 (uint32) (0.845490050944375 * (1 << DEFAULT_RADIX)),
<a name="l00108"></a>00108 (uint32) (0.857980995127572 * (1 << DEFAULT_RADIX)),
<a name="l00109"></a>00109 (uint32) (0.870364719583405 * (1 << DEFAULT_RADIX)),
<a name="l00110"></a>00110 (uint32) (0.882643049361841 * (1 << DEFAULT_RADIX)),
<a name="l00111"></a>00111 (uint32) (0.894817763307944 * (1 << DEFAULT_RADIX)),
<a name="l00112"></a>00112 (uint32) (0.906890595608518 * (1 << DEFAULT_RADIX)),
<a name="l00113"></a>00113 (uint32) (0.918863237274595 * (1 << DEFAULT_RADIX)),
<a name="l00114"></a>00114 (uint32) (0.930737337562886 * (1 << DEFAULT_RADIX)),
<a name="l00115"></a>00115 (uint32) (0.94251450533924 * (1 << DEFAULT_RADIX)),
<a name="l00116"></a>00116 (uint32) (0.954196310386875 * (1 << DEFAULT_RADIX)),
<a name="l00117"></a>00117 (uint32) (0.965784284662087 * (1 << DEFAULT_RADIX)),
<a name="l00118"></a>00118 (uint32) (0.977279923499917 * (1 << DEFAULT_RADIX)),
<a name="l00119"></a>00119 (uint32) (0.988684686772166 * (1 << DEFAULT_RADIX)),
<a name="l00120"></a>00120 };
<a name="l00121"></a>00121
<a name="l00122"></a>00122 int32
<a name="l00123"></a>00123 fixlog2(uint32 x)
<a name="l00124"></a>00124 {
<a name="l00125"></a>00125 uint32 y;
<a name="l00126"></a>00126
<a name="l00127"></a>00127 <span class="keywordflow">if</span> (x == 0)
<a name="l00128"></a>00128 <span class="keywordflow">return</span> MIN_FIXLOG2;
<a name="l00129"></a>00129
<a name="l00130"></a>00130 <span class="comment">/* Get the exponent. */</span>
<a name="l00131"></a>00131 <span class="preprocessor">#if defined(__GNUC__) && defined(__i386__) </span>
<a name="l00132"></a>00132 <span class="preprocessor"></span> __asm__(<span class="stringliteral">"bsrl %1, %0\n"</span>: <span class="stringliteral">"=r"</span>(y): <span class="stringliteral">"g"</span>(x):<span class="stringliteral">"cc"</span>);
<a name="l00133"></a>00133 x <<= (31 - y);
<a name="l00134"></a>00134 <span class="preprocessor">#elif defined(__ppc__)</span>
<a name="l00135"></a>00135 <span class="preprocessor"></span> __asm__(<span class="stringliteral">"cntlzw %0, %1\n"</span>: <span class="stringliteral">"=r"</span>(y):<span class="stringliteral">"r"</span>(x));
<a name="l00136"></a>00136 x <<= y;
<a name="l00137"></a>00137 y = 31 - y;
<a name="l00138"></a>00138 <span class="preprocessor">#elif ((defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5T__) || \</span>
<a name="l00139"></a>00139 <span class="preprocessor"> defined(__ARM_ARCH_5TE__)) && !defined(__thumb__))</span>
<a name="l00140"></a>00140 <span class="preprocessor"></span> __asm__(<span class="stringliteral">"clz %0, %1\n"</span>: <span class="stringliteral">"=r"</span>(y):<span class="stringliteral">"r"</span>(x));
<a name="l00141"></a>00141 x <<= y;
<a name="l00142"></a>00142 y = 31 - y;
<a name="l00143"></a>00143 <span class="preprocessor">#else</span>
<a name="l00144"></a>00144 <span class="preprocessor"></span> <span class="keywordflow">for</span> (y = 31; y >= 0; --y) {
<a name="l00145"></a>00145 <span class="keywordflow">if</span> (x & 0x80000000)
<a name="l00146"></a>00146 <span class="keywordflow">break</span>;
<a name="l00147"></a>00147 x <<= 1;
<a name="l00148"></a>00148 }
<a name="l00149"></a>00149 <span class="preprocessor">#endif</span>
<a name="l00150"></a>00150 <span class="preprocessor"></span> y <<= DEFAULT_RADIX;
<a name="l00151"></a>00151 <span class="comment">/* Do a table lookup for the MSB of the mantissa. */</span>
<a name="l00152"></a>00152 x = (x >> 25) & 0x3f;
<a name="l00153"></a>00153 <span class="keywordflow">return</span> y + logtable[x];
<a name="l00154"></a>00154 }
<a name="l00155"></a>00155
<a name="l00156"></a>00156 <span class="keywordtype">int</span>
<a name="l00157"></a>00157 fixlog(uint32 x)
<a name="l00158"></a>00158 {
<a name="l00159"></a>00159 int32 y;
<a name="l00160"></a>00160
<a name="l00161"></a>00161 <span class="keywordflow">if</span> (x == 0)
<a name="l00162"></a>00162 <span class="keywordflow">return</span> MIN_FIXLOG;
<a name="l00163"></a>00163
<a name="l00164"></a>00164 y = fixlog2(x);
<a name="l00165"></a>00165 <span class="keywordflow">return</span> FIXMUL(y, FIXLN_2);
<a name="l00166"></a>00166 }
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