diff options
| author | Tom Rondeau <tom@trondeau.com> | 2014-10-21 16:06:45 -0400 |
|---|---|---|
| committer | Tom Rondeau <tom@trondeau.com> | 2014-10-21 16:06:45 -0400 |
| commit | 5f4e68a60e96609fffe5478fb356798831201d87 (patch) | |
| tree | 8338a9129a68aeb74c5bcfd369c8d8821dd5bcf5 /gr-blocks/include/gnuradio/blocks/control_loop.h | |
| parent | 1b43ed159a7695cffde6b7a23b58333566aa4234 (diff) | |
blocks: adding a tanh lut for control_loop blocks to use.
Diffstat (limited to 'gr-blocks/include/gnuradio/blocks/control_loop.h')
| -rw-r--r-- | gr-blocks/include/gnuradio/blocks/control_loop.h | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/gr-blocks/include/gnuradio/blocks/control_loop.h b/gr-blocks/include/gnuradio/blocks/control_loop.h index f7ff9770f9..821c3824ec 100644 --- a/gr-blocks/include/gnuradio/blocks/control_loop.h +++ b/gr-blocks/include/gnuradio/blocks/control_loop.h @@ -268,6 +268,87 @@ namespace gr { float get_min_freq() const; }; + // This is a table of tanh(x) for x in [-2, 2] used in tanh_lut. + static float + tanh_lut_table[256] = { -0.96402758, -0.96290241, -0.96174273, -0.96054753, -0.95931576, + -0.95804636, -0.95673822, -0.95539023, -0.95400122, -0.95257001, + -0.95109539, -0.9495761 , -0.94801087, -0.94639839, -0.94473732, + -0.94302627, -0.94126385, -0.93944862, -0.93757908, -0.93565374, + -0.93367104, -0.93162941, -0.92952723, -0.92736284, -0.92513456, + -0.92284066, -0.92047938, -0.91804891, -0.91554743, -0.91297305, + -0.91032388, -0.90759795, -0.9047933 , -0.90190789, -0.89893968, + -0.89588656, -0.89274642, -0.88951709, -0.88619637, -0.88278203, + -0.87927182, -0.87566342, -0.87195453, -0.86814278, -0.86422579, + -0.86020115, -0.85606642, -0.85181914, -0.84745683, -0.84297699, + -0.83837709, -0.83365461, -0.82880699, -0.82383167, -0.81872609, + -0.81348767, -0.80811385, -0.80260204, -0.7969497 , -0.79115425, + -0.78521317, -0.77912392, -0.772884 , -0.76649093, -0.75994227, + -0.75323562, -0.74636859, -0.73933889, -0.73214422, -0.7247824 , + -0.71725127, -0.70954876, -0.70167287, -0.6936217 , -0.68539341, + -0.67698629, -0.66839871, -0.65962916, -0.65067625, -0.64153871, + -0.6322154 , -0.62270534, -0.61300768, -0.60312171, -0.59304692, + -0.58278295, -0.57232959, -0.56168685, -0.55085493, -0.53983419, + -0.52862523, -0.51722883, -0.50564601, -0.49387799, -0.48192623, + -0.46979241, -0.45747844, -0.44498647, -0.4323189 , -0.41947836, + -0.40646773, -0.39329014, -0.37994896, -0.36644782, -0.35279057, + -0.33898135, -0.32502449, -0.31092459, -0.2966865 , -0.28231527, + -0.26781621, -0.25319481, -0.23845682, -0.22360817, -0.208655 , + -0.19360362, -0.17846056, -0.16323249, -0.14792623, -0.13254879, + -0.11710727, -0.10160892, -0.08606109, -0.07047123, -0.05484686, + -0.0391956 , -0.02352507, -0.00784298, 0.00784298, 0.02352507, + 0.0391956 , 0.05484686, 0.07047123, 0.08606109, 0.10160892, + 0.11710727, 0.13254879, 0.14792623, 0.16323249, 0.17846056, + 0.19360362, 0.208655 , 0.22360817, 0.23845682, 0.25319481, + 0.26781621, 0.28231527, 0.2966865 , 0.31092459, 0.32502449, + 0.33898135, 0.35279057, 0.36644782, 0.37994896, 0.39329014, + 0.40646773, 0.41947836, 0.4323189 , 0.44498647, 0.45747844, + 0.46979241, 0.48192623, 0.49387799, 0.50564601, 0.51722883, + 0.52862523, 0.53983419, 0.55085493, 0.56168685, 0.57232959, + 0.58278295, 0.59304692, 0.60312171, 0.61300768, 0.62270534, + 0.6322154 , 0.64153871, 0.65067625, 0.65962916, 0.66839871, + 0.67698629, 0.68539341, 0.6936217 , 0.70167287, 0.70954876, + 0.71725127, 0.7247824 , 0.73214422, 0.73933889, 0.74636859, + 0.75323562, 0.75994227, 0.76649093, 0.772884 , 0.77912392, + 0.78521317, 0.79115425, 0.7969497 , 0.80260204, 0.80811385, + 0.81348767, 0.81872609, 0.82383167, 0.82880699, 0.83365461, + 0.83837709, 0.84297699, 0.84745683, 0.85181914, 0.85606642, + 0.86020115, 0.86422579, 0.86814278, 0.87195453, 0.87566342, + 0.87927182, 0.88278203, 0.88619637, 0.88951709, 0.89274642, + 0.89588656, 0.89893968, 0.90190789, 0.9047933 , 0.90759795, + 0.91032388, 0.91297305, 0.91554743, 0.91804891, 0.92047938, + 0.92284066, 0.92513456, 0.92736284, 0.92952723, 0.93162941, + 0.93367104, 0.93565374, 0.93757908, 0.93944862, 0.94126385, + 0.94302627, 0.94473732, 0.94639839, 0.94801087, 0.9495761 , + 0.95109539, 0.95257001, 0.95400122, 0.95539023, 0.95673822, + 0.95804636, 0.95931576, 0.96054753, 0.96174273, 0.96290241, + 0.96402758 }; + + /*! + * A look-up table (LUT) tanh calcuation. This function returns an + * estimate to tanh(x) based on a 256-point LUT between -2 and + * 2. If x < -2, it returns -1; if > 2, it retursn 1. + * + * This LUT form of the tanh is "hidden" in this code because it + * is likely too coarse an estimate for any real uses of a + * tanh. It is useful, however, in certain control loop + * applications where the input is expected to be within these + * bounds and the noise will be greater than the quanitzation of + * this small LUT. For more accurate forms of tanh, see + * volk_32f_tanh_32f. + */ + static inline float + tanhf_lut(float x) + { + if(x > 2) + return 1; + else if(x <= -2) + return -1; + else { + int index = 128 + 64*x; + return tanh_lut_table[index]; + } + } + } /* namespace blocks */ } /* namespace gr */ |