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-rw-r--r--web/api/queries/ses/ses.c92
1 files changed, 92 insertions, 0 deletions
diff --git a/web/api/queries/ses/ses.c b/web/api/queries/ses/ses.c
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+++ b/web/api/queries/ses/ses.c
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+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "ses.h"
+
+
+// ----------------------------------------------------------------------------
+// single exponential smoothing
+
+struct grouping_ses {
+ calculated_number alpha;
+ calculated_number alpha_other;
+ calculated_number level;
+ size_t count;
+};
+
+static size_t max_window_size = 15;
+
+void grouping_init_ses(void) {
+ long long ret = config_get_number(CONFIG_SECTION_WEB, "ses max window", (long long)max_window_size);
+ if(ret <= 1) {
+ config_set_number(CONFIG_SECTION_WEB, "ses max window", (long long)max_window_size);
+ }
+ else {
+ max_window_size = (size_t) ret;
+ }
+}
+
+static inline calculated_number window(RRDR *r, struct grouping_ses *g) {
+ (void)g;
+
+ calculated_number points;
+ if(r->group == 1) {
+ // provide a running DES
+ points = r->internal.points_wanted;
+ }
+ else {
+ // provide a SES with flush points
+ points = r->group;
+ }
+
+ return (points > max_window_size) ? max_window_size : points;
+}
+
+static inline void set_alpha(RRDR *r, struct grouping_ses *g) {
+ // https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
+ // A commonly used value for alpha is 2 / (N + 1)
+ g->alpha = 2.0 / (window(r, g) + 1.0);
+ g->alpha_other = 1.0 - g->alpha;
+}
+
+void *grouping_create_ses(RRDR *r) {
+ struct grouping_ses *g = (struct grouping_ses *)callocz(1, sizeof(struct grouping_ses));
+ set_alpha(r, g);
+ g->level = 0.0;
+ return g;
+}
+
+// resets when switches dimensions
+// so, clear everything to restart
+void grouping_reset_ses(RRDR *r) {
+ struct grouping_ses *g = (struct grouping_ses *)r->internal.grouping_data;
+ g->level = 0.0;
+ g->count = 0;
+}
+
+void grouping_free_ses(RRDR *r) {
+ freez(r->internal.grouping_data);
+ r->internal.grouping_data = NULL;
+}
+
+void grouping_add_ses(RRDR *r, calculated_number value) {
+ struct grouping_ses *g = (struct grouping_ses *)r->internal.grouping_data;
+
+ if(isnormal(value)) {
+ if(unlikely(!g->count))
+ g->level = value;
+
+ g->level = g->alpha * value + g->alpha_other * g->level;
+ g->count++;
+ }
+}
+
+calculated_number grouping_flush_ses(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) {
+ struct grouping_ses *g = (struct grouping_ses *)r->internal.grouping_data;
+
+ if(unlikely(!g->count || !isnormal(g->level))) {
+ *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY;
+ return 0.0;
+ }
+
+ return g->level;
+}