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#ifndef HISTO_HH
#define HISTO_HH
#include <cmath>
#include <ostream>
#include <vector>
#include <iterator>
#include <limits>
#include <algorithm>
#include <functional>
#include <numeric>
#include "common.hh"
#include "atomic.hh"
// Forward declaration.
template <typename T>
class Histogram;
/**
* An individual bin of histogram data.
*/
template <typename T>
class HistogramBin {
public:
/**
* Get a HistogramBin covering [s, e)
*/
HistogramBin(T s, T e) : _count(0), _start(s), _end(e) {}
/**
* The starting value of this histogram bin (inclusive).
*/
T start() const { return _start; }
/**
* The ending value of this histogram bin (exclusive).
*/
T end() const { return _end; }
/**
* The count in this bin.
*/
size_t count() const { return _count.get(); }
private:
friend class Histogram<T>;
/**
* Increment this bin by the given amount.
*/
void incr(size_t amount) {
_count.incr(amount);
}
/**
* Set a specific value for this bin.
*/
void set(size_t val) {
_count.set(val);
}
/**
* Does this bin contain the given value?
*
* @param value a value that may be within this bin's boundaries
* @return true if this value is counted within this bin
*/
bool accepts(T value) {
return value >= _start &&
(value < _end || value == std::numeric_limits<T>::max());
}
Atomic<size_t> _count;
T _start;
T _end;
DISALLOW_COPY_AND_ASSIGN(HistogramBin);
};
/**
* Helper function object to sum sample.
*/
template <typename T>
class HistogramBinSampleAdder {
public:
HistogramBinSampleAdder() {}
size_t operator() (size_t n, const HistogramBin<T> *b) { return n + b->count(); }
};
/**
* A bin generator that generates buckets of a width that may increase
* in size a fixed growth amount over iterations.
*/
template <typename T>
class GrowingWidthGenerator {
public:
/**
* Construct a growing width generator.
*
* @param start the starting point for this generator (inclusive)
* @param width the starting width for this generator
* @param growth how far the width should increase each time
*/
GrowingWidthGenerator(T start, T width, double growth=1.0)
: _growth(growth), _start(start), _width(static_cast<double>(width)) {}
/**
* Generate the next bin.
*/
HistogramBin<T>* operator () () {
HistogramBin<T>* rv = new HistogramBin<T>(_start,
_start + static_cast<T>(_width));
_start += static_cast<T>(_width);
_width = _width * _growth;
return rv;
}
private:
double _growth;
T _start;
double _width;
};
/**
* A bin generator that generates buckets from a sequence of T where
* each bin is from [v[n], v[n+1]).
*/
template <typename T>
class FixedInputGenerator {
public:
/**
* Get a FixedInputGenerator with the given sequence of bin starts.
*/
FixedInputGenerator(std::vector<T> &input)
: it(input.begin()), end(input.end()) {}
HistogramBin<T>* operator () () {
assert(it != end);
T current = *it;
++it;
assert(it != end);
T next = *it;
return new HistogramBin<T>(current, next);
}
private:
typename std::vector<T>::iterator it;
typename std::vector<T>::iterator end;
};
/**
* A bin generator that [n^i, n^(i+1)).
*/
template <typename T>
class ExponentialGenerator {
public:
/**
* Get a FixedInputGenerator with the given sequence of bin starts.
*/
ExponentialGenerator(uint64_t start, double power)
: _start(start), _power(power) {}
HistogramBin<T>* operator () () {
T start = static_cast<T>(std::pow(_power, static_cast<double>(_start)));
T end = static_cast<T>(std::pow(_power, static_cast<double>(++_start)));
return new HistogramBin<T>(start, end);
}
private:
uint64_t _start;
double _power;
};
/**
* Comparator for finding a histogram bin to hold a value.
*/
template <typename T>
class BinCompare {
public:
BinCompare() {}
bool operator() (T t, HistogramBin<T> *b) {
return t < b->end();
}
};
/**
* A Histogram.
*/
template <typename T>
class Histogram {
public:
/**
* Build a histogram.
*
* @param generator a generator for the bins within this bucket
* @param n how many bins this histogram should contain
*/
template <typename G>
Histogram(const G &generator, size_t n=30) : bins(n) {
fill(generator);
}
/**
* Build a default histogram.
*
* @param n how many bins this histogram should contain.
*/
Histogram(size_t n=30) : bins(n) {
ExponentialGenerator<T> generator(0, 2.0);
fill(generator);
}
~Histogram() {
for (typename std::vector<HistogramBin<T>*>::iterator it = bins.begin();
it != bins.end(); ++it) {
delete *it;
}
}
/**
* Add a value to this histogram.
*
* @param amount the size of the thing being added
* @param count the quantity at this size being added
*/
void add(T amount, size_t count=1) {
findBin(amount)->incr(count);
}
/**
* Get the bin servicing the given sized input.
*/
const HistogramBin<T>* getBin(T amount) {
return findBin(amount);
}
/**
* Set all bins to 0.
*/
void reset() {
std::for_each(bins.begin(), bins.end(),
std::bind2nd(std::mem_fun(&HistogramBin<T>::set), 0));
}
/**
* Get the total number of samples counted.
*
* This is the sum of all counts in each bin.
*/
size_t total() {
HistogramBinSampleAdder<T> a;
return std::accumulate(begin(), end(), 0, a);
}
/**
* A HistogramBin iterator.
*/
class iterator : public std::iterator<std::random_access_iterator_tag,
const Histogram<T>*> {
public:
iterator(typename std::vector<HistogramBin<T>*>::iterator x) :p(x) {}
iterator(const iterator& mit) : p(mit.p) {}
iterator& operator++() {++p;return *this;}
iterator& operator++(int) {iterator tmp(*this); operator++(); return tmp;}
bool operator==(const iterator& rhs) {return p==rhs.p;}
bool operator!=(const iterator& rhs) {return p!=rhs.p;}
const HistogramBin<T>* operator*() {return *p;}
private:
typename std::vector<HistogramBin<T>*>::iterator p;
friend class Histogram<T>;
};
/**
* Get an iterator from the beginning of a histogram bin.
*/
iterator begin() const {
return iterator(const_cast<Histogram<T>*>(this)->bins.begin());
}
/**
* Get the iterator at the end of the histogram bin.
*/
iterator end() const {
return iterator(const_cast<Histogram<T>*>(this)->bins.end());
}
private:
template <typename G>
void fill(G &generator) {
std::generate(bins.begin(), bins.end(), generator);
// If there will not naturally be one, create a bin for the
// smallest possible value
if (bins.front()->start() > std::numeric_limits<T>::min()) {
bins.insert(bins.begin(),
new HistogramBin<T>(std::numeric_limits<T>::min(),
bins.front()->start()));
}
// Also create one reaching to the largest possible value
if (bins.back()->end() < std::numeric_limits<T>::max()) {
bins.push_back(new HistogramBin<T>(bins.back()->end(),
std::numeric_limits<T>::max()));
}
verify();
}
// This validates that we're sorted and have no gaps or overlaps.
void verify() {
T prev = std::numeric_limits<T>::min();
typename std::vector<HistogramBin<T>*>::iterator it;
int pos(0);
for (it = bins.begin(); it != bins.end(); ++it) {
if ((*it)->start() != prev) {
std::cerr << "Expected " << (*it)->start() << " == " << prev
<< " at pos " << pos << std::endl;
abort();
}
assert((*it)->start() == prev);
prev = (*it)->end();
++pos;
}
assert(prev == std::numeric_limits<T>::max());
}
HistogramBin<T> *findBin(T amount) {
HistogramBin<T> *rv(NULL);
if (amount == std::numeric_limits<T>::max()) {
rv = bins.back();
} else {
typename std::vector<HistogramBin<T>*>::iterator it;
BinCompare<T> binCompare;
it = std::upper_bound(bins.begin(), bins.end(), amount, binCompare);
assert(it != bins.end());
assert((*it)->accepts(amount));
rv = *it;
}
return rv;
}
template <typename Ttype>
friend std::ostream& operator<< (std::ostream& out,
const Histogram<Ttype> &b);
std::vector<HistogramBin<T>*> bins;
DISALLOW_COPY_AND_ASSIGN(Histogram);
};
/**
* Times blocks automatically and records the values in a histogram.
*/
class BlockTimer {
public:
/**
* Get a BlockTimer that will store its values in the given
* histogram.
*
* @param d the histogram that will hold the result
*/
BlockTimer(Histogram<hrtime_t> *d, const char *n=NULL, std::ostream *o=NULL)
: dest(d), start(gethrtime()), name(n), out(o) {}
~BlockTimer() {
hrtime_t spent(gethrtime() - start);
dest->add(spent / 1000);
log(spent, name, out);
}
static inline void log(hrtime_t spent, const char *name, std::ostream *o) {
if (o && name) {
*o << name << "\t" << spent << "\n";
}
}
private:
Histogram<hrtime_t> *dest;
hrtime_t start;
const char *name;
std::ostream *out;
};
// How to print a bin.
template <typename T>
std::ostream& operator <<(std::ostream &out, const HistogramBin<T> &b) {
out << "[" << b.start() << ", " << b.end() << ") = " << b.count();
return out;
}
// How to print a vector histogram bin pointers
template <typename T>
std::ostream& operator <<(std::ostream &out, const std::vector<HistogramBin<T>*> &b) {
bool needComma(false);
for (typename std::vector<HistogramBin<T>*>::const_iterator it = b.begin();
it != b.end(); ++it) {
if (needComma) {
out << ", ";
}
out << **it;
needComma = true;
}
return out;
}
// How to print a histogram.
template <typename T>
std::ostream& operator <<(std::ostream &out, const Histogram<T> &b) {
out << "{Histogram: " << b.bins << "}";
return out;
}
#endif /* HISTO_HH */
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