cartographer源码分析(5)-common-fixed_ratio_sampler.h

源码可在https://github.com/learnmoreonce/SLAM 下载

文件:common/fixed_ratio_sampler.h#ifndef CARTOGRAPHER_COMMON_FIXED_RATIO_SAMPLER_H_#define CARTOGRAPHER_COMMON_FIXED_RATIO_SAMPLER_H_#include <string>#include "cartographer/common/port.h"namespace cartographer {namespace common {/*FixedRatioSampler是频率固定的采样器类，目的是从数据流中均匀的按照固定频率采样数据FixedRatioSampler不可拷贝,不可赋值.成员函数提供2种操作:Pulse()产生一个事件pulses,并且:如果计入采样samples，返回trueDebugString():以string形式输出采样率*/// Signals when a sample should be taken from a stream of data to select a// uniformly distributed fraction of the data.class FixedRatioSampler { public:  explicit FixedRatioSampler(double ratio);  ~FixedRatioSampler();  FixedRatioSampler(const FixedRatioSampler&) = delete;  FixedRatioSampler& operator=(const FixedRatioSampler&) = delete;  // Returns true if this pulse should result in an sample.  bool Pulse();  // Returns a debug string describing the current ratio of samples to pulses.  string DebugString(); private:  // Sampling occurs if the proportion of samples to pulses drops below this  // number.  const double ratio_;  int64 num_pulses_ = 0; //产生的脉冲次数  int64 num_samples_ = 0;//记录的采样次数};}  // namespace common}  // namespace cartographer#endif  // CARTOGRAPHER_COMMON_FIXED_RATIO_SAMPLER_H_

.

文件：fixed_ratio_sampler.cc:#include "cartographer/common/fixed_ratio_sampler.h"namespace cartographer {namespace common {FixedRatioSampler::FixedRatioSampler(const double ratio) : ratio_(ratio) {}FixedRatioSampler::~FixedRatioSampler() {}bool FixedRatioSampler::Pulse() {     //如果当前采样率 samples/ pulses低于固定采样率,此次事件计入采样.  ++num_pulses_;  if (static_cast<double>(num_samples_) / num_pulses_ < ratio_) {    ++num_samples_;    return true;  }  return false;}string FixedRatioSampler::DebugString() {  return std::to_string(num_samples_) + " (" +         std::to_string(100. * num_samples_ / num_pulses_) + "%)";}}  // namespace common}  // namespace cartographer

…

测试代码:#include "cartographer/common/fixed_ratio_sampler.h"#include "gtest/gtest.h"namespace cartographer {namespace common {namespace {TEST(FixedRatioSamplerTest, AlwaysTrue) {  FixedRatioSampler fixed_ratio_sampler(1.);//固定采样率是1hz，每次Pulse都采集samples  for (int i = 0; i < 100; ++i) {    EXPECT_TRUE(fixed_ratio_sampler.Pulse());  }}TEST(FixedRatioSamplerTest, AlwaysFalse) {  FixedRatioSampler fixed_ratio_sampler(0.);//0 hz，不采集samples  for (int i = 0; i < 100; ++i) {    EXPECT_FALSE(fixed_ratio_sampler.Pulse());  }}TEST(FixedRatioSamplerTest, SometimesTrue) {  FixedRatioSampler fixed_ratio_sampler(0.5); //0.5hz  for (int i = 0; i < 100; ++i) {    EXPECT_EQ(i % 2 == 0, fixed_ratio_sampler.Pulse());//每2次Pulse采集一次samples  }}TEST(FixedRatioSamplerTest, FirstPulseIsTrue) {  // Choose a very very small positive number for the ratio.  FixedRatioSampler fixed_ratio_sampler(1e-20); //0.000000...001hz  EXPECT_TRUE(fixed_ratio_sampler.Pulse());  for (int i = 0; i < 100; ++i) {    EXPECT_FALSE(fixed_ratio_sampler.Pulse()); //每100000000次Pulse采集一次samples  }}}  // namespace}  // namespace common}  // namespace cartographer

本文发于：
* http://www.jianshu.com/u/9e38d2febec1
* https://zhuanlan.zhihu.com/learnmoreonce
* http://blog.csdn.net/learnmoreonce
* slam源码分析微信公众号:slamcode