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authorSylvain Munaut <tnt@246tNt.com>2016-09-16 13:39:31 -0600
committerSylvain Munaut <tnt@246tNt.com>2016-12-30 09:39:22 +0100
commite82886ad0e13bb012e4a244df2ce6d84cd277763 (patch)
tree312435bcf6766a44f7785cf0fcf97e9e620c5a28 /src/cxvec_math.c
parentc3eabba5d240b99a48d8696b36a41dc17727a4e4 (diff)
cxvec/math: Add helper to find the N highest energy values in vector
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Diffstat (limited to 'src/cxvec_math.c')
-rw-r--r--src/cxvec_math.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/src/cxvec_math.c b/src/cxvec_math.c
index 9f81aa5..9dc6157 100644
--- a/src/cxvec_math.c
+++ b/src/cxvec_math.c
@@ -428,6 +428,51 @@ osmo_cxvec_interpolate_point(const struct osmo_cxvec *cv, float pos)
return val;
}
+/*! \brief Find the index of the N highest energy (\f$|x|^2\f$) peaks
+ * \param[in] cv Input complex vector
+ * \param[out] peaks_idx Return array of the peak indexes
+ * \param[in] Size of the \ref peaks_idx return array
+ * \returns Number of peaks (will be N if there is enough points)
+ */
+int
+osmo_cxvec_peaks_scan(const struct osmo_cxvec *cv, int *peaks_idx, int N)
+{
+ int i, j;
+ float peaks_mag[N];
+
+ /* Pre-init */
+ for (i=0; i<N; i++) {
+ peaks_idx[i] = -1;
+ peaks_mag[i] = 0.0f;
+ }
+
+ /* Scan all */
+ for (i=0; i<cv->len; i++)
+ {
+ /* Magnitude */
+ float mag = osmo_normsqf(cv->data[i]);
+
+ /* Worth it ? */
+ if (mag < peaks_mag[N-1])
+ continue;
+
+ /* Find insertion point in sorted array and pre-move */
+ for (j=N-1; j>0; j--) {
+ if (mag < peaks_mag[j-1])
+ break;
+
+ peaks_mag[j] = peaks_mag[j-1];
+ peaks_idx[j] = peaks_idx[j-1];
+ }
+
+ /* Do the insert */
+ peaks_mag[j] = mag;
+ peaks_idx[j] = i;
+ }
+
+ return i < N ? i : N;
+}
+
/*! \brief Find the maximum energy (\f$|x|^2\f$) peak in a sequence
* \param[in] cv Input complex vector
* \param[in] win_size Size of the window (for algorithms using windows)