diff options
| author | Marcus Müller <mueller@kit.edu> | 2020-02-13 21:01:56 +0100 |
|---|---|---|
| committer | Michael Dickens <michael.dickens@ettus.com> | 2020-02-14 10:05:12 -0500 |
| commit | d39d40c826a1b8e66c4789622c1287d439a26645 (patch) | |
| tree | 92c7fec137deb5fbe34d764cdbf526116c3c6dbf | |
| parent | aa0bd44efbf8afdfd93d627e486c1427426b76f9 (diff) | |
runtime/viterbi: get rid of GR_M_LOG2E constant
Constant was only used to emulate log_2 from ln.
Which is a strange thing to do on a computer with binary floating point
numbers.
Which is a superfluous thing to do when you have ::log2 in C++11.
| -rw-r--r-- | gnuradio-runtime/include/gnuradio/math.h | 2 | ||||
| -rw-r--r-- | gr-fec/lib/viterbi/metrics.cc | 15 |
2 files changed, 7 insertions, 10 deletions
diff --git a/gnuradio-runtime/include/gnuradio/math.h b/gnuradio-runtime/include/gnuradio/math.h index f628a5875c..e4e2d90315 100644 --- a/gnuradio-runtime/include/gnuradio/math.h +++ b/gnuradio-runtime/include/gnuradio/math.h @@ -28,7 +28,7 @@ * compile. GR_M_PI actually works with C++ but is defined here for the sake * of consistency. */ -#define GR_M_LOG2E 1.4426950408889634074 /* log_2 e */ + #define GR_M_PI 3.14159265358979323846 /* pi */ #define GR_M_PI_4 0.78539816339744830961566084582 /* pi/4 */ #define GR_M_TWOPI 6.28318530717958647692 /* 2*pi */ diff --git a/gr-fec/lib/viterbi/metrics.cc b/gr-fec/lib/viterbi/metrics.cc index c4c9b01af8..a000558276 100644 --- a/gr-fec/lib/viterbi/metrics.cc +++ b/gr-fec/lib/viterbi/metrics.cc @@ -35,9 +35,6 @@ /* Normal function integrated from -Inf to x. Range: 0-1 */ #define normal(x) (0.5 + 0.5 * erf((x) / GR_M_SQRT2)) -/* Logarithm base 2 */ -#define gr_log2(x) (log(x) * GR_M_LOG2E) - namespace gr { namespace fec { @@ -69,8 +66,8 @@ void gen_met(int mettab[2][256], /* Metric table, [sent sym][rx symbol] */ /* Prob of this value occurring for a 0-bit */ /* P(s|0) */ p0 = normal(((0 - OFFSET + 0.5) / amp + 1) / noise); - metrics[0][0] = gr_log2(2 * p0 / (p1 + p0)) - bias; - metrics[1][0] = gr_log2(2 * p1 / (p1 + p0)) - bias; + metrics[0][0] = ::log2(2 * p0 / (p1 + p0)) - bias; + metrics[1][0] = ::log2(2 * p1 / (p1 + p0)) - bias; for (s = 1; s < 255; s++) { /* P(s|1), prob of receiving s given 1 transmitted */ @@ -84,8 +81,8 @@ void gen_met(int mettab[2][256], /* Metric table, [sent sym][rx symbol] */ #ifdef notdef printf("P(%d|1) = %lg, P(%d|0) = %lg\n", s, p1, s, p0); #endif - metrics[0][s] = gr_log2(2 * p0 / (p1 + p0)) - bias; - metrics[1][s] = gr_log2(2 * p1 / (p1 + p0)) - bias; + metrics[0][s] = ::log2(2 * p0 / (p1 + p0)) - bias; + metrics[1][s] = ::log2(2 * p1 / (p1 + p0)) - bias; } /* 255 is also a special value */ /* P(s|1) */ @@ -93,8 +90,8 @@ void gen_met(int mettab[2][256], /* Metric table, [sent sym][rx symbol] */ /* P(s|0) */ p0 = 1 - normal(((255 - OFFSET - 0.5) / amp + 1) / noise); - metrics[0][255] = gr_log2(2 * p0 / (p1 + p0)) - bias; - metrics[1][255] = gr_log2(2 * p1 / (p1 + p0)) - bias; + metrics[0][255] = ::log2(2 * p0 / (p1 + p0)) - bias; + metrics[1][255] = ::log2(2 * p1 / (p1 + p0)) - bias; #ifdef notdef /* The probability of a raw symbol error is the probability * that a 1-bit would be received as a sample with value |