summaryrefslogtreecommitdiffstats
path: root/web/api/queries/des/des.c
diff options
context:
space:
mode:
Diffstat (limited to 'web/api/queries/des/des.c')
-rw-r--r--web/api/queries/des/des.c139
1 files changed, 139 insertions, 0 deletions
diff --git a/web/api/queries/des/des.c b/web/api/queries/des/des.c
new file mode 100644
index 0000000..93d7247
--- /dev/null
+++ b/web/api/queries/des/des.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include <web/api/queries/rrdr.h>
+#include "des.h"
+
+
+// ----------------------------------------------------------------------------
+// single exponential smoothing
+
+struct grouping_des {
+ calculated_number alpha;
+ calculated_number alpha_other;
+ calculated_number beta;
+ calculated_number beta_other;
+
+ calculated_number level;
+ calculated_number trend;
+
+ size_t count;
+};
+
+static size_t max_window_size = 15;
+
+void grouping_init_des(void) {
+ long long ret = config_get_number(CONFIG_SECTION_WEB, "des max window", (long long)max_window_size);
+ if(ret <= 1) {
+ config_set_number(CONFIG_SECTION_WEB, "des max window", (long long)max_window_size);
+ }
+ else {
+ max_window_size = (size_t) ret;
+ }
+}
+
+static inline calculated_number window(RRDR *r, struct grouping_des *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;
+ }
+
+ // https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
+ // A commonly used value for alpha is 2 / (N + 1)
+ return (points > max_window_size) ? max_window_size : points;
+}
+
+static inline void set_alpha(RRDR *r, struct grouping_des *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;
+
+ //info("alpha for chart '%s' is " CALCULATED_NUMBER_FORMAT, r->st->name, g->alpha);
+}
+
+static inline void set_beta(RRDR *r, struct grouping_des *g) {
+ // https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
+ // A commonly used value for alpha is 2 / (N + 1)
+
+ g->beta = 2.0 / (window(r, g) + 1.0);
+ g->beta_other = 1.0 - g->beta;
+
+ //info("beta for chart '%s' is " CALCULATED_NUMBER_FORMAT, r->st->name, g->beta);
+}
+
+void *grouping_create_des(RRDR *r) {
+ struct grouping_des *g = (struct grouping_des *)malloc(sizeof(struct grouping_des));
+ set_alpha(r, g);
+ set_beta(r, g);
+ g->level = 0.0;
+ g->trend = 0.0;
+ g->count = 0;
+ return g;
+}
+
+// resets when switches dimensions
+// so, clear everything to restart
+void grouping_reset_des(RRDR *r) {
+ struct grouping_des *g = (struct grouping_des *)r->internal.grouping_data;
+ g->level = 0.0;
+ g->trend = 0.0;
+ g->count = 0;
+
+ // fprintf(stderr, "\nDES: ");
+
+}
+
+void grouping_free_des(RRDR *r) {
+ freez(r->internal.grouping_data);
+ r->internal.grouping_data = NULL;
+}
+
+void grouping_add_des(RRDR *r, calculated_number value) {
+ struct grouping_des *g = (struct grouping_des *)r->internal.grouping_data;
+
+ if(isnormal(value)) {
+ if(likely(g->count > 0)) {
+ // we have at least a number so far
+
+ if(unlikely(g->count == 1)) {
+ // the second value we got
+ g->trend = value - g->trend;
+ g->level = value;
+ }
+
+ // for the values, except the first
+ calculated_number last_level = g->level;
+ g->level = (g->alpha * value) + (g->alpha_other * (g->level + g->trend));
+ g->trend = (g->beta * (g->level - last_level)) + (g->beta_other * g->trend);
+ }
+ else {
+ // the first value we got
+ g->level = g->trend = value;
+ }
+
+ g->count++;
+ }
+
+ //fprintf(stderr, "value: " CALCULATED_NUMBER_FORMAT ", level: " CALCULATED_NUMBER_FORMAT ", trend: " CALCULATED_NUMBER_FORMAT "\n", value, g->level, g->trend);
+}
+
+calculated_number grouping_flush_des(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) {
+ struct grouping_des *g = (struct grouping_des *)r->internal.grouping_data;
+
+ if(unlikely(!g->count || !isnormal(g->level))) {
+ *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY;
+ return 0.0;
+ }
+
+ //fprintf(stderr, " RESULT for %zu values = " CALCULATED_NUMBER_FORMAT " \n", g->count, g->level);
+
+ return g->level;
+}