math-cordic.js 2.8 KB

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  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 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. /////. Start CORDIC
  26. var AG_CONST = 0.6072529350;
  27. function FIXED(X)
  28. {
  29. return X * 65536.0;
  30. }
  31. function FLOAT(X)
  32. {
  33. return X / 65536.0;
  34. }
  35. function DEG2RAD(X)
  36. {
  37. return 0.017453 * (X);
  38. }
  39. var Angles = [
  40. FIXED(45.0), FIXED(26.565), FIXED(14.0362), FIXED(7.12502),
  41. FIXED(3.57633), FIXED(1.78991), FIXED(0.895174), FIXED(0.447614),
  42. FIXED(0.223811), FIXED(0.111906), FIXED(0.055953),
  43. FIXED(0.027977)
  44. ];
  45. var Target = 28.027;
  46. function cordicsincos(Target) {
  47. var X;
  48. var Y;
  49. var TargetAngle;
  50. var CurrAngle;
  51. var Step;
  52. X = FIXED(AG_CONST); /* AG_CONST * cos(0) */
  53. Y = 0; /* AG_CONST * sin(0) */
  54. TargetAngle = FIXED(Target);
  55. CurrAngle = 0;
  56. for (Step = 0; Step < 12; Step++) {
  57. var NewX;
  58. if (TargetAngle > CurrAngle) {
  59. NewX = X - (Y >> Step);
  60. Y = (X >> Step) + Y;
  61. X = NewX;
  62. CurrAngle += Angles[Step];
  63. } else {
  64. NewX = X + (Y >> Step);
  65. Y = -(X >> Step) + Y;
  66. X = NewX;
  67. CurrAngle -= Angles[Step];
  68. }
  69. }
  70. return FLOAT(X) * FLOAT(Y);
  71. }
  72. ///// End CORDIC
  73. var total = 0;
  74. function cordic( runs ) {
  75. var start = new Date();
  76. for ( var i = 0 ; i < runs ; i++ ) {
  77. total += cordicsincos(Target);
  78. }
  79. var end = new Date();
  80. return end.getTime() - start.getTime();
  81. }
  82. cordic(25000);
  83. var expected = 10362.570468755888;
  84. if (total != expected)
  85. throw "ERROR: bad result: expected " + expected + " but got " + total;