VILLASnode/common/lib/hist.cpp

/** Histogram class.
 *
 * @author Steffen Vogel <svogel2@eonerc.rwth-aachen.de>
 * @copyright 2014-2022, Institute for Automation of Complex Power Systems, EONERC
 * @license Apache License 2.0
 *********************************************************************************/

#include <cmath>
#include <algorithm>

#include <villas/utils.hpp>
#include <villas/hist.hpp>
#include <villas/config.hpp>
#include <villas/table.hpp>
#include <villas/exceptions.hpp>

using namespace villas;
using namespace villas::utils;

namespace villas {

Hist::Hist(int buckets, Hist::cnt_t wu) :
	resolution(0),
	high(0),
	low(0),
	highest(std::numeric_limits<double>::min()),
	lowest(std::numeric_limits<double>::max()),
	last(0),
	total(0),
	warmup(wu),
	higher(0),
	lower(0),
	data(buckets, 0),
	_m{0, 0},
	_s{0, 0}
{ }

void Hist::put(double value)
{
	last = value;

	/* Update min/max */
	if (value > highest)
		highest = value;
	if (value < lowest)
		lowest = value;

	if (data.size()) {
		if (total < warmup) {
			/* We are still in warmup phase... Waiting for more samples... */
		}
		else if (data.size() && total == warmup && warmup != 0) {
			low  = getMean() - 3 * getStddev();
			high = getMean() + 3 * getStddev();
			resolution = (high - low) / data.size();
		}
		else if (data.size() && (total == warmup) && (warmup == 0)) {
			// there is no warmup phase
			// TODO resolution = ?
		}
		else {
			idx_t idx = std::round((value - low) / resolution);

			/* Check bounds and increment */
			if      (idx >= (idx_t) data.size())
				higher++;
			else if (idx < 0)
				lower++;
			else
				data[idx]++;
		}
	}

	total++;

	/* Online / running calculation of variance and mean
	 *  by Donald Knuth’s Art of Computer Programming, Vol 2, page 232, 3rd edition */
	if (total == 1) {
		_m[1] = _m[0] = value;
		_s[1] = 0.0;
	}
	else {
		_m[0] = _m[1] + (value - _m[1]) / total;
		_s[0] = _s[1] + (value - _m[1]) * (value - _m[0]);

		/* Set up for next iteration */
		_m[1] = _m[0];
		_s[1] = _s[0];
	}
}

void Hist::reset()
{
	total = 0;
	higher = 0;
	lower = 0;

	highest = std::numeric_limits<double>::min();
	lowest  = std::numeric_limits<double>::max();

	for (auto &elm : data)
		elm = 0;
}

double Hist::getMean() const
{
	return total > 0 ? _m[0] : std::numeric_limits<double>::quiet_NaN();
}

double Hist::getVar() const
{
	return total > 1 ? _s[0] / (total - 1) : std::numeric_limits<double>::quiet_NaN();
}

double Hist::getStddev() const
{
	return sqrt(getVar());
}

void Hist::print(Logger logger, bool details) const
{
	if (total > 0) {
		Hist::cnt_t missed = total - higher - lower;

		logger->info("Counted values: {} ({} between {} and {})", total, missed, low, high);
		logger->info("Highest:  {:g}", highest);
		logger->info("Lowest:   {:g}", lowest);
		logger->info("Mu:       {:g}", getMean());
		logger->info("1/Mu:     {:g}", 1.0 / getMean());
		logger->info("Variance: {:g}", getVar());
		logger->info("Stddev:   {:g}", getStddev());

		if (details && total - higher - lower > 0) {
			char *buf = dump();
			logger->info("Matlab: {}", buf);
			free(buf);

			plot(logger);
		}
	}
	else
		logger->info("Counted values: {}", total);
}

void Hist::plot(Logger logger) const
{
	/* Get highest bar */
	Hist::cnt_t max = *std::max_element(data.begin(), data.end());

	std::vector<TableColumn> cols = {
		{ -9, TableColumn::Alignment::RIGHT, "Value", "%+9.3g" },
		{ -6, TableColumn::Alignment::RIGHT, "Count", "%6ju" },
		{  0, TableColumn::Alignment::LEFT,  "Plot",  "%s", "occurences" }
	};

	Table table = Table(logger, cols);

	/* Print plot */
	table.header();

	for (size_t i = 0; i < data.size(); i++) {
		double value = low + (i) * resolution;
		Hist::cnt_t cnt = data[i];
		int bar = cols[2].getWidth() * ((double) cnt / max);

		char *buf = strf("%s", "");
		for (int i = 0; i < bar; i++)
			buf = strcatf(&buf, "\u2588");

		table.row(3, value, cnt, buf);

		free(buf);
	}
}

char * Hist::dump() const
{
	char *buf = new char[128];
	if (!buf)
		throw MemoryAllocationError();

	memset(buf, 0, 128);

	strcatf(&buf, "[ ");

	for (auto elm : data)
		strcatf(&buf, "%ju ", elm);

	strcatf(&buf, "]");

	return buf;
}

json_t * Hist::toJson() const
{
	json_t *json_buckets, *json_hist;

	json_hist = json_pack("{ s: f, s: f, s: i }",
		"low", low,
		"high", high,
		"total", total
	);

	if (total > 0) {
		json_object_update(json_hist, json_pack("{ s: i, s: i, s: f, s: f, s: f, s: f, s: f }",
			"higher", higher,
			"lower", lower,
			"highest", highest,
			"lowest", lowest,
			"mean", getMean(),
			"variance", getVar(),
			"stddev", getStddev()
		));
	}

	if (total - lower - higher > 0) {
		json_buckets = json_array();

		for (auto elm : data)
			json_array_append(json_buckets, json_integer(elm));

		json_object_set(json_hist, "buckets", json_buckets);
	}

	return json_hist;
}

int Hist::dumpJson(FILE *f) const
{
	json_t *j = Hist::toJson();

	int ret = json_dumpf(j, f, 0);

	json_decref(j);

	return ret;
}

int Hist::dumpMatlab(FILE *f) const
{
	fprintf(f, "struct(");
	fprintf(f, "'low', %f, ", low);
	fprintf(f, "'high', %f, ", high);
	fprintf(f, "'total', %ju, ", total);
	fprintf(f, "'higher', %ju, ", higher);
	fprintf(f, "'lower', %ju, ", lower);
	fprintf(f, "'highest', %f, ", highest);
	fprintf(f, "'lowest', %f, ", lowest);
	fprintf(f, "'mean', %f, ", getMean());
	fprintf(f, "'variance', %f, ", getVar());
	fprintf(f, "'stddev', %f, ", getStddev());

	if (total - lower - higher > 0) {
		char *buf = dump();
		fprintf(f, "'buckets', %s", buf);
		free(buf);
	}
	else
		fprintf(f, "'buckets', zeros(1, %zu)", data.size());

	fprintf(f, ")");

	return 0;
}

} /* namespace villas */