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Diffstat (limited to 'gnuradio-runtime/lib/math/fast_atan2f.cc')
| -rw-r--r-- | gnuradio-runtime/lib/math/fast_atan2f.cc | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/gnuradio-runtime/lib/math/fast_atan2f.cc b/gnuradio-runtime/lib/math/fast_atan2f.cc new file mode 100644 index 0000000000..3555cf50ec --- /dev/null +++ b/gnuradio-runtime/lib/math/fast_atan2f.cc @@ -0,0 +1,202 @@ +/* -*- c++ -*- */ +/* + * Copyright 2005,2013 Free Software Foundation, Inc. + * + * This file is part of GNU Radio + * + * GNU Radio 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 3, or (at your option) + * any later version. + * + * GNU Radio 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 GNU Radio; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ + +#include <gnuradio/math.h> // declaration is in here +#include <cmath> + +namespace gr { + + /***************************************************************************/ + /* Constant definitions */ + /***************************************************************************/ + + #define TAN_MAP_RES 0.003921569 /* (smallest non-zero value in table) */ + #define RAD_PER_DEG 0.017453293 + #define TAN_MAP_SIZE 256 + + /* arctangents from 0 to pi/4 radians */ + static float + fast_atan_table[257] = { + 0.000000e+00, 3.921549e-03, 7.842976e-03, 1.176416e-02, + 1.568499e-02, 1.960533e-02, 2.352507e-02, 2.744409e-02, + 3.136226e-02, 3.527947e-02, 3.919560e-02, 4.311053e-02, + 4.702413e-02, 5.093629e-02, 5.484690e-02, 5.875582e-02, + 6.266295e-02, 6.656816e-02, 7.047134e-02, 7.437238e-02, + 7.827114e-02, 8.216752e-02, 8.606141e-02, 8.995267e-02, + 9.384121e-02, 9.772691e-02, 1.016096e-01, 1.054893e-01, + 1.093658e-01, 1.132390e-01, 1.171087e-01, 1.209750e-01, + 1.248376e-01, 1.286965e-01, 1.325515e-01, 1.364026e-01, + 1.402496e-01, 1.440924e-01, 1.479310e-01, 1.517652e-01, + 1.555948e-01, 1.594199e-01, 1.632403e-01, 1.670559e-01, + 1.708665e-01, 1.746722e-01, 1.784728e-01, 1.822681e-01, + 1.860582e-01, 1.898428e-01, 1.936220e-01, 1.973956e-01, + 2.011634e-01, 2.049255e-01, 2.086818e-01, 2.124320e-01, + 2.161762e-01, 2.199143e-01, 2.236461e-01, 2.273716e-01, + 2.310907e-01, 2.348033e-01, 2.385093e-01, 2.422086e-01, + 2.459012e-01, 2.495869e-01, 2.532658e-01, 2.569376e-01, + 2.606024e-01, 2.642600e-01, 2.679104e-01, 2.715535e-01, + 2.751892e-01, 2.788175e-01, 2.824383e-01, 2.860514e-01, + 2.896569e-01, 2.932547e-01, 2.968447e-01, 3.004268e-01, + 3.040009e-01, 3.075671e-01, 3.111252e-01, 3.146752e-01, + 3.182170e-01, 3.217506e-01, 3.252758e-01, 3.287927e-01, + 3.323012e-01, 3.358012e-01, 3.392926e-01, 3.427755e-01, + 3.462497e-01, 3.497153e-01, 3.531721e-01, 3.566201e-01, + 3.600593e-01, 3.634896e-01, 3.669110e-01, 3.703234e-01, + 3.737268e-01, 3.771211e-01, 3.805064e-01, 3.838825e-01, + 3.872494e-01, 3.906070e-01, 3.939555e-01, 3.972946e-01, + 4.006244e-01, 4.039448e-01, 4.072558e-01, 4.105574e-01, + 4.138496e-01, 4.171322e-01, 4.204054e-01, 4.236689e-01, + 4.269229e-01, 4.301673e-01, 4.334021e-01, 4.366272e-01, + 4.398426e-01, 4.430483e-01, 4.462443e-01, 4.494306e-01, + 4.526070e-01, 4.557738e-01, 4.589307e-01, 4.620778e-01, + 4.652150e-01, 4.683424e-01, 4.714600e-01, 4.745676e-01, + 4.776654e-01, 4.807532e-01, 4.838312e-01, 4.868992e-01, + 4.899573e-01, 4.930055e-01, 4.960437e-01, 4.990719e-01, + 5.020902e-01, 5.050985e-01, 5.080968e-01, 5.110852e-01, + 5.140636e-01, 5.170320e-01, 5.199904e-01, 5.229388e-01, + 5.258772e-01, 5.288056e-01, 5.317241e-01, 5.346325e-01, + 5.375310e-01, 5.404195e-01, 5.432980e-01, 5.461666e-01, + 5.490251e-01, 5.518738e-01, 5.547124e-01, 5.575411e-01, + 5.603599e-01, 5.631687e-01, 5.659676e-01, 5.687566e-01, + 5.715357e-01, 5.743048e-01, 5.770641e-01, 5.798135e-01, + 5.825531e-01, 5.852828e-01, 5.880026e-01, 5.907126e-01, + 5.934128e-01, 5.961032e-01, 5.987839e-01, 6.014547e-01, + 6.041158e-01, 6.067672e-01, 6.094088e-01, 6.120407e-01, + 6.146630e-01, 6.172755e-01, 6.198784e-01, 6.224717e-01, + 6.250554e-01, 6.276294e-01, 6.301939e-01, 6.327488e-01, + 6.352942e-01, 6.378301e-01, 6.403565e-01, 6.428734e-01, + 6.453808e-01, 6.478788e-01, 6.503674e-01, 6.528466e-01, + 6.553165e-01, 6.577770e-01, 6.602282e-01, 6.626701e-01, + 6.651027e-01, 6.675261e-01, 6.699402e-01, 6.723452e-01, + 6.747409e-01, 6.771276e-01, 6.795051e-01, 6.818735e-01, + 6.842328e-01, 6.865831e-01, 6.889244e-01, 6.912567e-01, + 6.935800e-01, 6.958943e-01, 6.981998e-01, 7.004964e-01, + 7.027841e-01, 7.050630e-01, 7.073330e-01, 7.095943e-01, + 7.118469e-01, 7.140907e-01, 7.163258e-01, 7.185523e-01, + 7.207701e-01, 7.229794e-01, 7.251800e-01, 7.273721e-01, + 7.295557e-01, 7.317307e-01, 7.338974e-01, 7.360555e-01, + 7.382053e-01, 7.403467e-01, 7.424797e-01, 7.446045e-01, + 7.467209e-01, 7.488291e-01, 7.509291e-01, 7.530208e-01, + 7.551044e-01, 7.571798e-01, 7.592472e-01, 7.613064e-01, + 7.633576e-01, 7.654008e-01, 7.674360e-01, 7.694633e-01, + 7.714826e-01, 7.734940e-01, 7.754975e-01, 7.774932e-01, + 7.794811e-01, 7.814612e-01, 7.834335e-01, 7.853983e-01, + 7.853983e-01 + }; + + + /***************************************************************************** + Function: Arc tangent + + Syntax: angle = fast_atan2(y, x); + float y y component of input vector + float x x component of input vector + float angle angle of vector (x, y) in radians + + Description: This function calculates the angle of the vector (x,y) + based on a table lookup and linear interpolation. The table uses a + 256 point table covering -45 to +45 degrees and uses symetry to + determine the final angle value in the range of -180 to 180 + degrees. Note that this function uses the small angle approximation + for values close to zero. This routine calculates the arc tangent + with an average error of +/- 0.045 degrees. + *****************************************************************************/ + + float + fast_atan2f(float y, float x) + { + float x_abs, y_abs, z; + float alpha, angle, base_angle; + int index; + + /* don't divide by zero! */ // FIXME could get hosed with -0.0 + if((y == 0.0) && (x == 0.0)) + return 0.0; + + /* normalize to +/- 45 degree range */ + y_abs = fabsf(y); + x_abs = fabsf(x); + //z = (y_abs < x_abs ? y_abs / x_abs : x_abs / y_abs); + if(y_abs < x_abs) + z = y_abs / x_abs; + else + z = x_abs / y_abs; + + /* when ratio approaches the table resolution, the angle is */ + /* best approximated with the argument itself... */ + if(z < TAN_MAP_RES) + base_angle = z; + else { + /* find index and interpolation value */ + alpha = z * (float)TAN_MAP_SIZE - .5; + index = (int)alpha; + alpha -= (float)index; + /* determine base angle based on quadrant and */ + /* add or subtract table value from base angle based on quadrant */ + base_angle = fast_atan_table[index]; + base_angle += + (fast_atan_table[index + 1] - fast_atan_table[index]) * alpha; + } + + if(x_abs > y_abs) { /* -45 -> 45 or 135 -> 225 */ + if(x >= 0.0) { /* -45 -> 45 */ + if(y >= 0.0) + angle = base_angle; /* 0 -> 45, angle OK */ + else + angle = -base_angle; /* -45 -> 0, angle = -angle */ + } + else { /* 135 -> 180 or 180 -> -135 */ + angle = 3.14159265358979323846; + if(y >= 0.0) + angle -= base_angle; /* 135 -> 180, angle = 180 - angle */ + else + angle = base_angle - angle; /* 180 -> -135, angle = angle - 180 */ + } + } + else { /* 45 -> 135 or -135 -> -45 */ + if(y >= 0.0) { /* 45 -> 135 */ + angle = 1.57079632679489661923; + if(x >= 0.0) + angle -= base_angle; /* 45 -> 90, angle = 90 - angle */ + else + angle += base_angle; /* 90 -> 135, angle = 90 + angle */ + } + else { /* -135 -> -45 */ + angle = -1.57079632679489661923; + if(x >= 0.0) + angle += base_angle; /* -90 -> -45, angle = -90 + angle */ + else + angle -= base_angle; /* -135 -> -90, angle = -90 - angle */ + } + } + + #ifdef ZERO_TO_TWOPI + if (angle < 0) + return (angle + TWOPI); + else + return (angle); + #else + return (angle); + #endif + } + +} /* namespace gr */ |