/*
** Copyright (C) 2001-2025 Zabbix SIA
**
** This program is free software: you can redistribute it and/or modify it under the terms of
** the GNU Affero General Public License as published by the Free Software Foundation, version 3.
**
** This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
** without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
** See the GNU Affero General Public License for more details.
**
** You should have received a copy of the GNU Affero General Public License along with this program.
** If not, see <https://www.gnu.org/licenses/>.
**/
#include "zbxeval.h"
#include "zbxnum.h"
#include "zbxalgo.h"
typedef struct
{
double upper;
double count;
}
zbx_histogram_t;
ZBX_VECTOR_DECL(histogram, zbx_histogram_t)
ZBX_VECTOR_IMPL(histogram, zbx_histogram_t)
static int zbx_is_normal_double(double dbl)
{
if (FP_ZERO != fpclassify(dbl) && FP_NORMAL != fpclassify(dbl))
return FAIL;
return SUCCEED;
}
/******************************************************************************
* *
* Purpose: calculates arithmetic mean (i.e. average) *
* *
* Parameters: v - [IN] non-empty vector with input data *
* *
* Return value: arithmetic mean value *
* *
******************************************************************************/
static double calc_arithmetic_mean(const zbx_vector_dbl_t *v)
{
double sum = 0;
int i;
for (i = 0; i < v->values_num; i++)
sum += v->values[i];
return sum / v->values_num;
}
/******************************************************************************
* *
* Purpose: evaluates function 'kurtosis' *
* *
* Parameters: values - [IN] non-empty vector with input data *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
******************************************************************************/
int zbx_eval_calc_kurtosis(zbx_vector_dbl_t *values, double *result, char **error)
{
double mean, second_moment = 0, fourth_moment = 0, second_moment2, res;
int i;
/* step 1: calculate arithmetic mean */
mean = calc_arithmetic_mean(values);
if (SUCCEED != zbx_is_normal_double(mean))
goto err;
/* step 2: calculate the second and the fourth moments */
for (i = 0; i < values->values_num; i++)
{
double diff = values->values[i] - mean;
second_moment += diff * diff;
fourth_moment += diff * diff * diff * diff;
}
second_moment /= values->values_num;
fourth_moment /= values->values_num;
/* step 3: calculate kurtosis */
second_moment2 = second_moment * second_moment;
if (FP_NORMAL != fpclassify(second_moment2) || SUCCEED != zbx_is_normal_double(fourth_moment))
goto err;
res = fourth_moment / second_moment2;
if (SUCCEED != zbx_is_normal_double(res))
goto err;
*result = res;
return SUCCEED;
err:
*error = zbx_strdup(*error, "cannot calculate kurtosis() value");
return FAIL;
}
/******************************************************************************
* *
* Purpose: finds median (helper function) *
* *
* Parameters: v - [IN/OUT] non-empty vector with input data *
* NOTE: it will be modified (sorted in place). *
* *
* Return value: median *
* *
******************************************************************************/
static double find_median(zbx_vector_dbl_t *v)
{
zbx_vector_dbl_sort(v, ZBX_DEFAULT_DBL_COMPARE_FUNC);
if (0 == v->values_num % 2) /* number of elements is even */
return (v->values[v->values_num / 2 - 1] + v->values[v->values_num / 2]) / 2.0;
else
return v->values[v->values_num / 2];
}
/******************************************************************************
* *
* Purpose: calculates 'median absolute deviation' *
* *
* Parameters: values - [IN] non-empty vector with input data *
* NOTE: its elements will be modified and should *
* not be used in the caller! *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
******************************************************************************/
int zbx_eval_calc_mad(zbx_vector_dbl_t *values, double *result, char **error)
{
double median;
int i;
/* step 1: find median of input data */
median = find_median(values);
if (SUCCEED != zbx_is_normal_double(median))
goto err;
/* step 2: find absolute differences of input data and median. Reuse input data vector. */
for (i = 0; i < values->values_num; i++)
values->values[i] = fabs(values->values[i] - median);
/* step 3: find median of the differences */
median = find_median(values);
if (SUCCEED != zbx_is_normal_double(median))
goto err;
*result = median;
return SUCCEED;
err:
*error = zbx_strdup(*error, "cannot calculate mad() value");
return FAIL;
}
/******************************************************************************
* *
* Purpose: evaluates 'skewness' function *
* *
* Parameters: values - [IN] non-empty vector with input data *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
******************************************************************************/
int zbx_eval_calc_skewness(zbx_vector_dbl_t *values, double *result, char **error)
{
double mean, std_dev = 0, sum_diff3 = 0, divisor;
int i;
/* step 1: calculate arithmetic mean */
mean = calc_arithmetic_mean(values);
if (SUCCEED != zbx_is_normal_double(mean))
goto err;
/* step 2: calculate the standard deviation and sum_diff3 */
for (i = 0; i < values->values_num; i++)
{
double diff = values->values[i] - mean;
std_dev += diff * diff;
sum_diff3 += diff * diff * diff;
}
std_dev = sqrt(std_dev / values->values_num);
/* step 3: calculate skewness */
divisor = values->values_num * std_dev * std_dev * std_dev;
if (FP_NORMAL != fpclassify(divisor) || SUCCEED != zbx_is_normal_double(sum_diff3))
goto err;
*result = sum_diff3 / divisor;
return SUCCEED;
err:
*error = zbx_strdup(*error, "cannot calculate skewness() value");
return FAIL;
}
/******************************************************************************
* *
* Purpose: evaluates function 'stdevpop' (population standard deviation) *
* *
* Parameters: values - [IN] non-empty vector with input data *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
* Comments: algorithm was taken from "Population standard deviation of *
* grades of eight students" in *
* https://en.wikipedia.org/wiki/Standard_deviation *
* *
******************************************************************************/
int zbx_eval_calc_stddevpop(zbx_vector_dbl_t *values, double *result, char **error)
{
double mean, std_dev = 0;
int i;
/* step 1: calculate arithmetic mean */
mean = calc_arithmetic_mean(values);
if (SUCCEED != zbx_is_normal_double(mean))
goto err;
/* step 2: calculate the standard deviation */
for (i = 0; i < values->values_num; i++)
{
double diff = values->values[i] - mean;
std_dev += diff * diff;
}
std_dev = sqrt(std_dev / values->values_num);
if (SUCCEED != zbx_is_normal_double(std_dev))
goto err;
*result = std_dev;
return SUCCEED;
err:
*error = zbx_strdup(*error, "cannot calculate stddevpop() value");
return FAIL;
}
/******************************************************************************
* *
* Purpose: evaluates function 'stddevsamp' (sample standard deviation) *
* *
* Parameters: values - [IN] vector with input data with at least 2 elements *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
* Comments: algorithm was taken from "Population standard deviation of *
* grades of eight students" in *
* https://en.wikipedia.org/wiki/Standard_deviation *
* *
******************************************************************************/
int zbx_eval_calc_stddevsamp(zbx_vector_dbl_t *values, double *result, char **error)
{
double mean, std_dev = 0;
int i;
if (2 > values->values_num) /* stddevsamp requires at least 2 data values */
{
*error = zbx_strdup(*error, "not enough data");
return FAIL;
}
/* step 1: calculate arithmetic mean */
mean = calc_arithmetic_mean(values);
if (SUCCEED != zbx_is_normal_double(mean))
goto err;
/* step 2: calculate the standard deviation */
for (i = 0; i < values->values_num; i++)
{
double diff = values->values[i] - mean;
std_dev += diff * diff;
}
std_dev = sqrt(std_dev / (values->values_num - 1)); /* divided by 'n - 1' because */
/* sample standard deviation */
if (SUCCEED != zbx_is_normal_double(std_dev))
goto err;
*result = std_dev;
return SUCCEED;
err:
*error = zbx_strdup(*error, "cannot calculate stddevsamp() value");
return FAIL;
}
/******************************************************************************
* *
* Purpose: calculates sum of squares *
* *
* Parameters: values - [IN] non-empty vector with input data *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
******************************************************************************/
int zbx_eval_calc_sumofsquares(zbx_vector_dbl_t *values, double *result, char **error)
{
double sum = 0;
int i;
for (i = 0; i < values->values_num; i++)
sum += values->values[i] * values->values[i];
if (SUCCEED != zbx_is_normal_double(sum))
{
*error = zbx_strdup(*error, "cannot calculate sumofsquares() value");
return FAIL;
}
*result = sum;
return SUCCEED;
}
/******************************************************************************
* *
* Purpose: evaluates function 'varpop' (population variance) *
* *
* Parameters: values - [IN] non-empty vector with input data *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
* Comments: algorithm was taken from "Population variance" in *
* https://en.wikipedia.org/wiki/Variance#Population_variance *
* *
******************************************************************************/
int zbx_eval_calc_varpop(zbx_vector_dbl_t *values, double *result, char **error)
{
double mean, res = 0;
int i;
/* step 1: calculate arithmetic mean */
mean = calc_arithmetic_mean(values);
if (SUCCEED != zbx_is_normal_double(mean))
goto err;
/* step 2: calculate the population variance */
for (i = 0; i < values->values_num; i++)
{
double diff = values->values[i] - mean;
res += diff * diff;
}
res /= values->values_num; /* divide by 'number of values' for population variance */
if (SUCCEED != zbx_is_normal_double(res))
goto err;
*result = res;
return SUCCEED;
err:
*error = zbx_strdup(*error, "cannot calculate varpop() value");
return FAIL;
}
/******************************************************************************
* *
* Purpose: evaluates function 'varsamp' (sample variance) *
* *
* Parameters: values - [IN] non-empty vector with input data *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
* Comments: algorithm was taken from "Sample variance" in *
* https://en.wikipedia.org/wiki/Variance#Population_variance *
* *
******************************************************************************/
int zbx_eval_calc_varsamp(zbx_vector_dbl_t *values, double *result, char **error)
{
double mean, res = 0;
int i;
if (2 > values->values_num) /* varsamp requires at least 2 data values */
{
*error = zbx_strdup(*error, "not enough data");
return FAIL;
}
/* step 1: calculate arithmetic mean */
mean = calc_arithmetic_mean(values);
if (SUCCEED != zbx_is_normal_double(mean))
goto err;
/* step 2: calculate the sample variance */
for (i = 0; i < values->values_num; i++)
{
double diff = values->values[i] - mean;
res += diff * diff;
}
res /= values->values_num - 1; /* divide by 'number of values' - 1 for unbiased sample variance */
if (SUCCEED != zbx_is_normal_double(res))
goto err;
*result = res;
return SUCCEED;
err:
*error = zbx_strdup(*error, "cannot calculate varsamp() value");
return FAIL;
}
static void remove_duplicate_backet(zbx_vector_histogram_t *h)
{
zbx_histogram_t b, last = h->values[0];
int i, inx = 0;
for (i = 1; i < h->values_num; i++)
{
b = h->values[i];
if (SUCCEED == zbx_double_compare(b.upper, last.upper))
{
last.count += b.count;
}
else
{
h->values[inx] = last;
last = b;
inx++;
}
}
h->values[inx] = last;
while (h->values_num > inx + 1)
zbx_vector_histogram_remove_noorder(h, h->values_num - 1);
}
static void ensure_histogram_monotonic(zbx_vector_histogram_t *h)
{
double max = h->values[0].count;
int i;
for (i = 1; i < h->values_num; i++)
{
if (h->values[i].count > max)
max = h->values[i].count;
else if (h->values[i].count < max)
h->values[i].count = max;
}
}
/******************************************************************************
* *
* Purpose: calculates histogram quantile base on vector, where odd position *
* is bucket upper bound ('le') and even position is 'rate' value *
* *
* Parameters: q - [IN] quantile value from 0 till 1 *
* values - [IN] non-empty vector with input data *
* err_fn - [IN] function name for error info *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
******************************************************************************/
int zbx_eval_calc_histogram_quantile(const double q, const zbx_vector_dbl_t *values, const char *err_fn,
double *result, char **error)
{
# define LAST(v) v.values[v.values_num - 1]
zbx_vector_histogram_t histogram;
double res, total, rank, count, end, start;
zbx_histogram_t hg;
int i, ret = FAIL;
if (0 == values->values_num)
{
*error = zbx_dsprintf(*error, "invalid parameter: number of histogram buckets must not be zero"
" for function at \"%s\"",err_fn);
return FAIL;
}
zbx_vector_histogram_create(&histogram);
for (i = 0; i < values->values_num;)
{
hg.upper = values->values[i++];
hg.count = values->values[i++];
zbx_vector_histogram_append(&histogram, hg);
}
if (histogram.values_num < 2)
{
*error = zbx_dsprintf(*error, "invalid number of rate buckets for function at \"%s\"",err_fn);
goto err;
}
zbx_vector_histogram_sort(&histogram, ZBX_DEFAULT_DBL_COMPARE_FUNC);
if (FP_INFINITE != fpclassify(LAST(histogram).upper))
{
*error = zbx_dsprintf(*error, "invalid last infinity rate buckets for function at \"%s\"", err_fn);
goto err;
}
remove_duplicate_backet(&histogram);
if (histogram.values_num < 2)
{
*error = zbx_dsprintf(*error,
"invalid number of rate buckets with duplicates for function at \"%s\"", err_fn);
goto err;
}
ensure_histogram_monotonic(&histogram);
total = LAST(histogram).count;
if (FP_ZERO == fpclassify(total))
{
res = -1; /* preprocessing pending with discard value */
goto end;
}
rank = q * total;
for (i = 0; i < histogram.values_num - 1; i++)
{
if (histogram.values[i].count >= rank)
break;
}
if (i == histogram.values_num - 1)
{
res = histogram.values[histogram.values_num - 2].upper;
goto end;
}
if (0 == i && 0 >= histogram.values[0].upper)
{
res = histogram.values[0].upper;
goto end;
}
start = 0;
end = histogram.values[i].upper;
count = histogram.values[i].count;
if (i > 0)
{
start = histogram.values[i - 1].upper;
count -= histogram.values[i - 1].count;
rank -= histogram.values[i - 1].count;
}
res = start + (end - start) * (rank / count);
end:
if (SUCCEED != zbx_is_normal_double(res))
{
*error = zbx_dsprintf(*error, "cannot calculate value for function at \"%s\"", err_fn);
goto err;
}
*result = res;
ret = SUCCEED;
err:
zbx_vector_histogram_destroy(&histogram);
return ret;
}
/******************************************************************************
* *
* Purpose: evaluates function avg *
* *
* Parameters: values - [IN] non-empty vector with input data *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
******************************************************************************/
int zbx_eval_calc_avg(zbx_vector_dbl_t *values, double *result, char **error)
{
if (0 == values->values_num)
{
*error = zbx_strdup(*error, "no data (at least one value is required)");
return FAIL;
}
*result = calc_arithmetic_mean(values);
return SUCCEED;
}
/******************************************************************************
* *
* Purpose: evaluates function min *
* *
* Parameters: values - [IN] non-empty vector with input data *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
******************************************************************************/
int zbx_eval_calc_min(zbx_vector_dbl_t *values, double *result, char **error)
{
double value;
int i;
if (0 == values->values_num)
{
*error = zbx_strdup(*error, "no data (at least one value is required)");
return FAIL;
}
value = values->values[0];
for (i = 1; i < values->values_num; i++)
{
if (values->values[i] < value)
value = values->values[i];
}
*result = value;
return SUCCEED;
}
/******************************************************************************
* *
* Purpose: evaluates function max *
* *
* Parameters: values - [IN] non-empty vector with input data *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
******************************************************************************/
int zbx_eval_calc_max(zbx_vector_dbl_t *values, double *result, char **error)
{
double value;
int i;
if (0 == values->values_num)
{
*error = zbx_strdup(*error, "no data (at least one value is required)");
return FAIL;
}
value = values->values[0];
for (i = 1; i < values->values_num; i++)
{
if (values->values[i] > value)
value = values->values[i];
}
*result = value;
return SUCCEED;
}
/******************************************************************************
* *
* Purpose: evaluates function sum *
* *
* Parameters: values - [IN] non-empty vector with input data *
* result - [OUT] calculated value *
* error - [OUT] dynamically allocated error message *
* *
* Return value: SUCCEED - evaluated successfully *
* FAIL - failed to evaluate function (see 'error') *
* *
******************************************************************************/
int zbx_eval_calc_sum(zbx_vector_dbl_t *values, double *result, char **error)
{
double value;
int i;
if (0 == values->values_num)
{
*error = zbx_strdup(*error, "no data (at least one value is required)");
return FAIL;
}
value = 0;
for (i = 0; i < values->values_num; i++)
value += values->values[i];
*result = value;
return SUCCEED;
}