js/src/t/math-cordic.js

   1 /*
   2  * Copyright (C) Rich Moore.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY CONTRIBUTORS ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 /////. Start CORDIC
  27
  28 var AG_CONST = 0.6072529350;
  29
  30 function FIXED(X)
  31 {
  32   return X * 65536.0;
  33 }
  34
  35 function FLOAT(X)
  36 {
  37   return X / 65536.0;
  38 }
  39
  40 function DEG2RAD(X)
  41 {
  42   return 0.017453 * (X);
  43 }
  44
  45 var Angles = [
  46   FIXED(45.0), FIXED(26.565), FIXED(14.0362), FIXED(7.12502),
  47   FIXED(3.57633), FIXED(1.78991), FIXED(0.895174), FIXED(0.447614),
  48   FIXED(0.223811), FIXED(0.111906), FIXED(0.055953),
  49   FIXED(0.027977)
  50               ];
  51
  52
  53 function cordicsincos() {
  54     var X;
  55     var Y;
  56     var TargetAngle;
  57     var CurrAngle;
  58     var Step;
  59
  60     X = FIXED(AG_CONST);         /* AG_CONST * cos(0) */
  61     Y = 0;                       /* AG_CONST * sin(0) */
  62
  63     TargetAngle = FIXED(28.027);
  64     CurrAngle = 0;
  65     for (Step = 0; Step < 12; Step++) {
  66         var NewX;
  67         if (TargetAngle > CurrAngle) {
  68             NewX = X - (Y >> Step);
  69             Y = (X >> Step) + Y;
  70             X = NewX;
  71             CurrAngle += Angles[Step];
  72         } else {
  73             NewX = X + (Y >> Step);
  74             Y = -(X >> Step) + Y;
  75             X = NewX;
  76             CurrAngle -= Angles[Step];
  77         }
  78     }
  79 }
  80
  81 ///// End CORDIC
  82
  83 function cordic( runs ) {
  84   var start = new Date();
  85
  86   for ( var i = 0 ; i < runs ; i++ ) {
  87       cordicsincos();
  88   }
  89
  90   var end = new Date();
  91
  92   return end.getTime() - start.getTime();
  93 }
  94
  95 cordic(25000);