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132 lines
3.7 KiB
C++
132 lines
3.7 KiB
C++
// histogram.cc
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/**
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* Copyright (C) 2010 10gen Inc.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License, version 3,
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <iomanip>
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#include <limits>
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#include <sstream>
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#include "histogram.h"
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namespace mongo {
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using std::ostringstream;
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using std::setfill;
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using std::setw;
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Histogram::Histogram( const Options& opts )
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: _initialValue( opts.initialValue )
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, _numBuckets( opts.numBuckets )
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, _boundaries( new uint32_t[_numBuckets] )
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, _buckets( new uint64_t[_numBuckets] ) {
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// TODO more sanity checks
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// + not too few buckets
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// + initialBucket and bucketSize fit within 32 bit ints
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// _boundaries store the maximum value falling in that bucket.
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if ( opts.exponential ) {
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uint32_t twoPow = 1; // 2^0
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for ( uint32_t i = 0; i < _numBuckets - 1; i++) {
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_boundaries[i] = _initialValue + opts.bucketSize * twoPow;
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twoPow *= 2; // 2^i+1
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}
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}
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else {
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_boundaries[0] = _initialValue + opts.bucketSize;
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for ( uint32_t i = 1; i < _numBuckets - 1; i++ ) {
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_boundaries[i] = _boundaries[ i-1 ] + opts.bucketSize;
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}
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}
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_boundaries[ _numBuckets-1 ] = std::numeric_limits<uint32_t>::max();
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for ( uint32_t i = 0; i < _numBuckets; i++ ) {
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_buckets[i] = 0;
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}
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}
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Histogram::~Histogram() {
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delete [] _boundaries;
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delete [] _buckets;
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}
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void Histogram::insert( uint32_t element ) {
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if ( element < _initialValue) return;
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_buckets[ _findBucket(element) ] += 1;
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}
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string Histogram::toHTML() const {
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uint64_t max = 0;
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for ( uint32_t i = 0; i < _numBuckets; i++ ) {
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if ( _buckets[i] > max ) {
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max = _buckets[i];
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}
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}
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if ( max == 0 ) {
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return "histogram is empty\n";
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}
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// normalize buckets to max
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const int maxBar = 20;
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ostringstream ss;
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for ( uint32_t i = 0; i < _numBuckets; i++ ) {
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int barSize = _buckets[i] * maxBar / max;
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ss << string( barSize,'*' )
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<< setfill(' ') << setw( maxBar-barSize + 12 )
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<< _boundaries[i] << '\n';
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}
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return ss.str();
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}
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uint64_t Histogram::getCount( uint32_t bucket ) const {
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if ( bucket >= _numBuckets ) return 0;
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return _buckets[ bucket ];
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}
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uint32_t Histogram::getBoundary( uint32_t bucket ) const {
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if ( bucket >= _numBuckets ) return 0;
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return _boundaries[ bucket ];
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}
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uint32_t Histogram::getBucketsNum() const {
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return _numBuckets;
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}
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uint32_t Histogram::_findBucket( uint32_t element ) const {
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// TODO assert not too small a value?
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uint32_t low = 0;
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uint32_t high = _numBuckets - 1;
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while ( low < high ) {
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// low + ( (high - low) / 2 );
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uint32_t mid = ( low + high ) >> 1;
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if ( element > _boundaries[ mid ] ) {
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low = mid + 1;
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}
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else {
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high = mid;
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}
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}
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return low;
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}
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} // namespace mongo
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