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1 // SPDX-License-Identifier: GPL-3.0-or-later
2
3 #ifndef NETDATA_API_QUERIES_DES_H
4 #define NETDATA_API_QUERIES_DES_H
5
6 #include "../query.h"
7 #include "../rrdr.h"
8
9 struct tg_des {
10 NETDATA_DOUBLE alpha;
11 NETDATA_DOUBLE alpha_other;
12 NETDATA_DOUBLE beta;
13 NETDATA_DOUBLE beta_other;
14
15 NETDATA_DOUBLE level;
16 NETDATA_DOUBLE trend;
17
18 size_t count;
19 };
20
21 static size_t tg_des_max_window_size = 15;
22
23 static inline void tg_des_init(void) {
24 long long ret = inicfg_get_number(&netdata_config, CONFIG_SECTION_WEB, "des max tg_des_window", (long long)tg_des_max_window_size);
25 if(ret <= 1) {
26 inicfg_set_number(&netdata_config, CONFIG_SECTION_WEB, "des max tg_des_window", (long long)tg_des_max_window_size);
27 }
28 else {
29 tg_des_max_window_size = (size_t) ret;
30 }
31 }
32
33 static inline NETDATA_DOUBLE tg_des_window(RRDR *r, struct tg_des *g) {
34 (void)g;
35
36 NETDATA_DOUBLE points;
37 if(r->view.group == 1) {
38 // provide a running DES
39 points = (NETDATA_DOUBLE)r->time_grouping.points_wanted;
40 }
41 else {
42 // provide a SES with flush points
43 points = (NETDATA_DOUBLE)r->view.group;
44 }
45
46 // https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
47 // A commonly used value for alpha is 2 / (N + 1)
48 return (points > (NETDATA_DOUBLE)tg_des_max_window_size) ? (NETDATA_DOUBLE)tg_des_max_window_size : points;
49 }
50
51 static inline void tg_des_set_alpha(RRDR *r, struct tg_des *g) {
52 // https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
53 // A commonly used value for alpha is 2 / (N + 1)
54
55 g->alpha = 2.0 / (tg_des_window(r, g) + 1.0);
56 g->alpha_other = 1.0 - g->alpha;
57
58 //info("alpha for chart '%s' is " CALCULATED_NUMBER_FORMAT, r->st->name, g->alpha);
59 }
60
61 static inline void tg_des_set_beta(RRDR *r, struct tg_des *g) {
62 // https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
63 // A commonly used value for alpha is 2 / (N + 1)
64
65 g->beta = 2.0 / (tg_des_window(r, g) + 1.0);
66 g->beta_other = 1.0 - g->beta;
67
68 //info("beta for chart '%s' is " CALCULATED_NUMBER_FORMAT, r->st->name, g->beta);
69 }
70
71 static inline void tg_des_create(RRDR *r, const char *options __maybe_unused) {
72 struct tg_des *g = (struct tg_des *)onewayalloc_mallocz(r->internal.owa, sizeof(struct tg_des));
73 tg_des_set_alpha(r, g);
74 tg_des_set_beta(r, g);
75 g->level = 0.0;
76 g->trend = 0.0;
77 g->count = 0;
78 r->time_grouping.data = g;
79 }
80
81 // resets when switches dimensions
82 // so, clear everything to restart
83 static inline void tg_des_reset(RRDR *r) {
84 struct tg_des *g = (struct tg_des *)r->time_grouping.data;
85 g->level = 0.0;
86 g->trend = 0.0;
87 g->count = 0;
88
89 // fprintf(stderr, "\nDES: ");
90
91 }
92
93 static inline void tg_des_free(RRDR *r) {
94 onewayalloc_freez(r->internal.owa, r->time_grouping.data);
95 r->time_grouping.data = NULL;
96 }
97
98 static inline void tg_des_add(RRDR *r, NETDATA_DOUBLE value) {
99 struct tg_des *g = (struct tg_des *)r->time_grouping.data;
100
101 if(likely(g->count > 0)) {
102 // we have at least a number so far
103
104 if(unlikely(g->count == 1)) {
105 // the second value we got
106 g->trend = value - g->trend;
107 g->level = value;
108 }
109
110 // for the values, except the first
111 NETDATA_DOUBLE last_level = g->level;
112 g->level = (g->alpha * value) + (g->alpha_other * (g->level + g->trend));
113 g->trend = (g->beta * (g->level - last_level)) + (g->beta_other * g->trend);
114 }
115 else {
116 // the first value we got
117 g->level = g->trend = value;
118 }
119
120 g->count++;
121
122 //fprintf(stderr, "value: " CALCULATED_NUMBER_FORMAT ", level: " CALCULATED_NUMBER_FORMAT ", trend: " CALCULATED_NUMBER_FORMAT "\n", value, g->level, g->trend);
123 }
124
125 static inline NETDATA_DOUBLE tg_des_flush(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) {
126 struct tg_des *g = (struct tg_des *)r->time_grouping.data;
127
128 if(unlikely(!g->count || !netdata_double_isnumber(g->level))) {
129 *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY;
130 return 0.0;
131 }
132
133 //fprintf(stderr, " RESULT for %zu values = " CALCULATED_NUMBER_FORMAT " \n", g->count, g->level);
134
135 return g->level;
136 }
137
138 #endif //NETDATA_API_QUERIES_DES_H