Quick and dirty way to profile your code

Question

What method do you use when you want to get performance data about specific code paths?

Answer 1

I use this class when the problem at hand doesn't justify profiling all my code or I get some data from a profiler that I want to verify. What it basically does is sum up the time you spent in a specific block and at the end of the program outputs it to the debug stream (viewable with DbgView) including how many times the code was executed (and the average time spent of course).

#pragma once 
#include <tchar.h>
#include <windows.h>
#include <sstream>
#include <boost/noncopyable.hpp>

namespace scope_timer {
    class time_collector : boost::noncopyable {
     __int64 total;
     LARGE_INTEGER start;
     size_t times;
     const TCHAR* name;

     double cpu_frequency() { // cache the CPU frequency, which doesn't change.
      static double ret = 0; // store as double so devision later on is floating point and not truncating
      if (ret == 0) { 
       LARGE_INTEGER freq;
       QueryPerformanceFrequency(&freq);
       ret = static_cast<double>(freq.QuadPart);
      }
      return ret;
     }

    public:
     time_collector(const TCHAR* n) : times(0), name(n), total(0), start(LARGE_INTEGER()) { }
     ~time_collector() {  
      std::basic_ostringstream<TCHAR> msg;
      msg << _T("scope_timer> ") <<  name << _T(" called: ");

      double seconds = total / cpu_frequency();
      double average = seconds / times;

      msg << times << _T(" times total time: ") << seconds << _T(" seconds  ")
       << _T(" (avg ") << average <<_T(")\n");
      OutputDebugString(msg.str().c_str());
     }

     void add_time(__int64 ticks) { 
      total += ticks;
      ++times;
     }
    };

    class one_time :  boost::noncopyable {
     LARGE_INTEGER start;
     time_collector& collector;
    public:
     one_time(time_collector& tc) : collector(tc) {
      QueryPerformanceCounter(&start);
     }
     ~one_time() { 
      LARGE_INTEGER end;
      QueryPerformanceCounter(&end);
      collector.add_time(end.QuadPart - start.QuadPart); 
     }
    };
} 

// Usage TIME_THIS_SCOPE(XX); where XX is a C variable name (can begin with a number)
#define TIME_THIS_SCOPE(name) \
    static scope_timer::time_collector st_time_collector_##name(_T(#name)); \
    scope_timer::one_time st_one_time_##name(st_time_collector_##name)

Answer 2

Well, I have 2 code snippets. In pseudo code they are looking like (it's a simplified version, I'm using QueryPerformanceFrequency actually)

1st snippet:

Timer timer = new Timer
timer.Start

2nd snippet:

timer.Stop
show elapsed time

A bit of hot-keys kung fu and I can say how much time this piece of code stole from my CPU

Answer 3

This article has lots of information about C++ code profiling and also has a free download link to a program/class that will show you a graphic presentation for different code paths/methods:

http://www.codeproject.com/KB/cpp/profiler.aspx

Answer 4

Related Question: How do you profile your code

Answer 5

I do my profiles by creating two class: cProfile and cProfileManager.

cProfileManager will hold all the data that resulted from cProfile.

cProfile with have the following requirements:

• cProfile have a constructor which initializes the current time.
• cProfile have a deconstructor which sends the total time the class was alive to cProfileManager

To use this profile classes, I first make an instance of cProfileManager. Then, I put the code block which I want to profile inside curly braces. Inside the curly braces, I create a cProfile instance. When the code block ends, cProfile will send the time it took for the block of code to finish to cProfileManager.

Example Code

Here's an example of the code (simplified):

class cProfile
{
    cProfile()
    {
     TimeStart = GetTime();
    };

    ~cProfile()
    {
     ProfileManager->AddProfile (GetTime() - TimeStart);
    }

    float TimeStart;
}

To use cProfile, I would do something like this:

int main()
{
    printf("Start test");

    {
     cProfile Profile;

     Calculate();
    }

    ProfileManager->OutputData();
}

or this:

void foobar()
{
    cProfile ProfileFoobar;

    foo();

    {    
     cProfile ProfileBarCheck;

     while (bar())
     {
      cProfile ProfileSpam;

      spam();
     }
    }
}

Technical Note

This code is actually an abuse of the way scoping, constructors and deconstructors work in c++. cProfile exists only inside the block scope (the code block we want to test). Once the program leaves the block scope, cProfile records the result.

Additional Enhancements

• You can add a string parameter to the constructor so you can do something like this: cProfile Profile("Profile for complicated calculation");

• You can use a macro to make the code look cleaner (be careful not to abuse this. Unlike our other abuses on the language, macros can be dangerous when used).

  Example:

  #define START_PROFILE cProfile Profile(); {
  #define END_PROFILE }

• cProfileManager can check how many times a block of code is called. But you would need an identifier for the block of code. The first enhancement can help identify the block. This can be useful in cases where the code you want to profile is inside a loop (like the second example aboe). You can also add the average, fastest and longest execution time the code block took.

• Don't forget to add a check to skip profiling if you are in debug mode.

Answer 6

I have a quick-and-dirty profiling class that can be used in profiling even the most tight inner loops. The emphasis is on extreme light weight and simple code. The class allocates a two-dimensional array of fixed size. I then add "checkpoint" calls all over the place. When checkpoint N is reached immediately after checkpoint M, I add the time elapsed (in microseconds) to the array item [M,N]. Since this is designed to profile tight loops, I also have "start of iteration" call that resets the the "last checkpoint" variable. At the end of test, dumpResults() call produces the list of all pairs of checkpoints that followed each other, together with total time accounted for and unaccounted for.

Answer 7

I also have a timer class that I wrote to do quick-and-dirty profiling that uses QueryPerformanceCounter() to get high-precision timings, but with a slight difference. My timer class doesn't dump the elapsed time when the Timer object falls out of scope. Instead, it accumulates the elapsed times in to an collection. I added a static member function, Dump(), which creates a table of elapsed times, sorted by timing category (specified in Timer's constructor as a string) along with some statistical analysis such as mean elapsed time, standard deviation, max and min. I also added a Clear() static member function which clears the collection & lets you start over again.

Note, this was all written specifically for Windows.

How to use the Timer class (psudocode):

int CInsertBuffer::Read(char* pBuf)
{
       // TIMER NOTES: Avg Execution Time = ~1 ms
       Timer timer("BufferRead");
       :      :
       return -1;
}

Sample output :

Timer Precision = 418.0095 ps

=== Item               Trials    Ttl Time  Avg Time  Mean Time StdDev    ===
    AddTrade           500       7 ms      14 us     12 us     24 us
    BufferRead         511       1:19.25   0.16 s    621 ns    2.48 s
    BufferWrite        516       511 us    991 ns    482 ns    11 us
    ImportPos Loop     1002      18.62 s   19 ms     77 us     0.51 s
    ImportPosition     2         18.75 s   9.38 s    16.17 s   13.59 s
    Insert             515       4.26 s    8 ms      5 ms      27 ms
    recv               101       18.54 s   0.18 s    2603 ns   1.63 s

file Timer.inl :

#include <map>
#include "x:\utils\stlext\stringext.h"
#include <iterator>
#include <set>
#include <vector>
#include <numeric>
#include "x:\utils\stlext\algorithmext.h"
#include <math.h>

    class Timer
    {
    public:
     Timer(const char* name)
     {
      label = std::safe_string(name);
      QueryPerformanceCounter(&startTime);
     }

     virtual ~Timer()
     {
      QueryPerformanceCounter(&stopTime);
      __int64 clocks = stopTime.QuadPart-startTime.QuadPart;
      double elapsed = (double)clocks/(double)TimerFreq();
      TimeMap().insert(std::make_pair(label,elapsed));
     };

     static std::string Dump(bool ClipboardAlso=true)
     {
      static const std::string loc = "Timer::Dump";

      if( TimeMap().empty() )
      {
       return "No trials\r\n";
      }

      std::string ret = std::formatstr("\r\n\r\nTimer Precision = %s\r\n\r\n", format_elapsed(1.0/(double)TimerFreq()).c_str());

      // get a list of keys
      typedef std::set<std::string> keyset;
      keyset keys;
      std::transform(TimeMap().begin(), TimeMap().end(), std::inserter(keys, keys.begin()), extract_key());

      size_t maxrows = 0;

      typedef std::vector<std::string> strings;
      strings lines;

      static const size_t tabWidth = 9;

      std::string head = std::formatstr("=== %-*.*s %-*.*s %-*.*s %-*.*s %-*.*s %-*.*s ===", tabWidth*2, tabWidth*2, "Item", tabWidth, tabWidth, "Trials", tabWidth, tabWidth, "Ttl Time", tabWidth, tabWidth, "Avg Time", tabWidth, tabWidth, "Mean Time", tabWidth, tabWidth, "StdDev");
      ret += std::formatstr("\r\n%s\r\n", head.c_str());
      if( ClipboardAlso ) 
       lines.push_back("Item\tTrials\tTtl Time\tAvg Time\tMean Time\tStdDev\r\n");
      // dump the values for each key
      {for( keyset::iterator key = keys.begin(); keys.end() != key; ++key )
      {
       time_type ttl = 0;
       ttl = std::accumulate(TimeMap().begin(), TimeMap().end(), ttl, accum_key(*key));
       size_t num = std::count_if( TimeMap().begin(), TimeMap().end(), match_key(*key));
       if( num > maxrows ) 
        maxrows = num;
       time_type avg = ttl / num;

       // compute mean
       std::vector<time_type> sortedTimes;
       std::transform_if(TimeMap().begin(), TimeMap().end(), std::inserter(sortedTimes, sortedTimes.begin()), extract_val(), match_key(*key));
       std::sort(sortedTimes.begin(), sortedTimes.end());
       size_t mid = (size_t)floor((double)num/2.0);
       double mean = ( num > 1 && (num % 2) != 0 ) ? (sortedTimes[mid]+sortedTimes[mid+1])/2.0 : sortedTimes[mid];
       // compute variance
       double sum = 0.0;
       if( num > 1 )
       {
        for( std::vector<time_type>::iterator timeIt = sortedTimes.begin(); sortedTimes.end() != timeIt; ++timeIt )
         sum += pow(*timeIt-mean,2.0);
       }
       // compute std dev
       double stddev = num > 1 ? sqrt(sum/((double)num-1.0)) : 0.0;

       ret += std::formatstr("    %-*.*s %-*.*s %-*.*s %-*.*s %-*.*s %-*.*s\r\n", tabWidth*2, tabWidth*2, key->c_str(), tabWidth, tabWidth, std::formatstr("%d",num).c_str(), tabWidth, tabWidth, format_elapsed(ttl).c_str(), tabWidth, tabWidth, format_elapsed(avg).c_str(), tabWidth, tabWidth, format_elapsed(mean).c_str(), tabWidth, tabWidth, format_elapsed(stddev).c_str()); 
       if( ClipboardAlso )
        lines.push_back(std::formatstr("%s\t%s\t%s\t%s\t%s\t%s\r\n", key->c_str(), std::formatstr("%d",num).c_str(), format_elapsed(ttl).c_str(), format_elapsed(avg).c_str(), format_elapsed(mean).c_str(), format_elapsed(stddev).c_str())); 

      }
      }
      ret += std::formatstr("%s\r\n", std::string(head.length(),'=').c_str());

      if( ClipboardAlso )
      {
       // dump header row of data block
       lines.push_back("");
       {
        std::string s;
        for( keyset::iterator key = keys.begin(); key != keys.end(); ++key )
        {
         if( key != keys.begin() )
          s.append("\t");
         s.append(*key);
        }
        s.append("\r\n");
        lines.push_back(s);
       }

       // blow out the flat map of time values to a seperate vector of times for each key
       typedef std::map<std::string, std::vector<time_type> > nodematrix;
       nodematrix nodes;
       for( Times::iterator time = TimeMap().begin(); time != TimeMap().end(); ++time )
        nodes[time->first].push_back(time->second);

       // dump each data point
       for( size_t row = 0; row < maxrows; ++row )
       {
        std::string rowDump;
        for( keyset::iterator key = keys.begin(); key != keys.end(); ++key )
        {
         if( key != keys.begin() )
          rowDump.append("\t");
         if( nodes[*key].size() > row )
          rowDump.append(std::formatstr("%f", nodes[*key][row]));
        }
        rowDump.append("\r\n");
        lines.push_back(rowDump);
       }

       // dump to the clipboard
       std::string dump;
       for( strings::iterator s = lines.begin(); s != lines.end(); ++s )
       {
        dump.append(*s);
       }

       OpenClipboard(0);
       EmptyClipboard();
       HGLOBAL hg = GlobalAlloc(GMEM_MOVEABLE, dump.length()+1);
       if( hg != 0 )
       {
        char* buf = (char*)GlobalLock(hg);
        if( buf != 0 )
        {
         std::copy(dump.begin(), dump.end(), buf);
         buf[dump.length()] = 0;
         GlobalUnlock(hg);
         SetClipboardData(CF_TEXT, hg);
        }
       }
       CloseClipboard();
      }

      return ret;
     }

     static void Reset()
     {
      TimeMap().clear();
     }

     static std::string format_elapsed(double d) 
     {
      if( d < 0.00000001 )
      {
       // show in ps with 4 digits
       return std::formatstr("%0.4f ps", d * 1000000000000.0);
      }
      if( d < 0.00001 )
      {
       // show in ns
       return std::formatstr("%0.0f ns", d * 1000000000.0);
      }
      if( d < 0.001 )
      {
       // show in us
       return std::formatstr("%0.0f us", d * 1000000.0);
      }
      if( d < 0.1 )
      {
       // show in ms
       return std::formatstr("%0.0f ms", d * 1000.0);
      }
      if( d <= 60.0 )
      {
       // show in seconds
       return std::formatstr("%0.2f s", d);
      }
      if( d < 3600.0 )
      {
       // show in min:sec
       return std::formatstr("%01.0f:%02.2f", floor(d/60.0), fmod(d,60.0));
      }
      // show in h:min:sec
      return std::formatstr("%01.0f:%02.0f:%02.2f", floor(d/3600.0), floor(fmod(d,3600.0)/60.0), fmod(d,60.0));
     }

    private:
     static __int64 TimerFreq()
     {
      static __int64 freq = 0;
      static bool init = false;
      if( !init )
      {
       LARGE_INTEGER li;
       QueryPerformanceFrequency(&li);
       freq = li.QuadPart;
       init = true;
      }
      return freq;
     }
     LARGE_INTEGER startTime, stopTime;
     std::string label;

     typedef std::string key_type;
     typedef double time_type;
     typedef std::multimap<key_type, time_type> Times;
//   static Times times;
     static Times& TimeMap()
     {
      static Times times_;
      return times_;
     }

     struct extract_key : public std::unary_function<Times::value_type, key_type>
     {
      std::string operator()(Times::value_type const & r) const
      {
       return r.first;
      }
     };

     struct extract_val : public std::unary_function<Times::value_type, time_type>
     {
      time_type operator()(Times::value_type const & r) const
      {
       return r.second;
      }
     };
     struct match_key : public std::unary_function<Times::value_type, bool>
     {
      match_key(key_type const & key_) : key(key_) {};
      bool operator()(Times::value_type const & rhs) const
      {
       return key == rhs.first;
      }
     private:
      match_key& operator=(match_key&) { return * this; }
      const key_type key;
     };

     struct accum_key : public std::binary_function<time_type, Times::value_type, time_type>
     {
      accum_key(key_type const & key_) : key(key_), n(0) {};
      time_type operator()(time_type const & v, Times::value_type const & rhs) const
      {
       if( key == rhs.first )
       {
        ++n;
        return rhs.second + v;
       }
       return v;
      }
     private:
      accum_key& operator=(accum_key&) { return * this; }
      const Times::key_type key;
      mutable size_t n;
     };
    };

file stringext.h (provides formatstr() function):

namespace std
{
    /* ---

    Formatted Print

     template<class C>
     int strprintf(basic_string<C>* pString, const C* pFmt, ...);

     template<class C>
     int vstrprintf(basic_string<C>* pString, const C* pFmt, va_list args);

    Returns :

     # characters printed to output


    Effects :

     Writes formatted data to a string.  strprintf() works exactly the same as sprintf(); see your
     documentation for sprintf() for details of peration.  vstrprintf() also works the same as sprintf(), 
     but instead of accepting a variable paramater list it accepts a va_list argument.

    Requires :

     pString is a pointer to a basic_string<>

    --- */

    template<class char_type> int vprintf_generic(char_type* buffer, size_t bufferSize, const char_type* format, va_list argptr);

    template<> inline int vprintf_generic<char>(char* buffer, size_t bufferSize, const char* format, va_list argptr)
    {
#    ifdef SECURE_VSPRINTF
     return _vsnprintf_s(buffer, bufferSize-1, _TRUNCATE, format, argptr);
#    else
     return _vsnprintf(buffer, bufferSize-1, format, argptr);
#    endif
    }

    template<> inline int vprintf_generic<wchar_t>(wchar_t* buffer, size_t bufferSize, const wchar_t* format, va_list argptr)
    {
#    ifdef SECURE_VSPRINTF
     return _vsnwprintf_s(buffer, bufferSize-1, _TRUNCATE, format, argptr);
#    else
     return _vsnwprintf(buffer, bufferSize-1, format, argptr);
#    endif
    }

    template<class Type, class Traits>
    inline int vstringprintf(basic_string<Type,Traits> & outStr, const Type* format, va_list args)
    {
     // prologue
     static const size_t ChunkSize = 1024;
     size_t curBufSize = 0;
     outStr.erase(); 

     if( !format )
     {
      return 0;
     }

     // keep trying to write the string to an ever-increasing buffer until
     // either we get the string written or we run out of memory
     while( bool cont = true )
     {
      // allocate a local buffer
      curBufSize += ChunkSize;
      std::ref_ptr<Type> localBuffer = new Type[curBufSize];
      if( localBuffer.get() == 0 )
      {
       // we ran out of memory -- nice goin'!
       return -1;
      }
      // format output to local buffer
      int i = vprintf_generic(localBuffer.get(), curBufSize * sizeof(Type), format, args);
      if( -1 == i )
      {
       // the buffer wasn't big enough -- try again
       continue;
      }
      else if( i < 0 )
      {
       // something wierd happened -- bail
       return i;
      }
      // if we get to this point the string was written completely -- stop looping
      outStr.assign(localBuffer.get(),i);
      return i;
     }
     // unreachable code
     return -1;
    };

    // provided for backward-compatibility
    template<class Type, class Traits>
    inline int vstrprintf(basic_string<Type,Traits> * outStr, const Type* format, va_list args)
    {
     return vstringprintf(*outStr, format, args);
    }

    template<class Char, class Traits>
    inline int stringprintf(std::basic_string<Char, Traits> & outString, const Char* format, ...)
    {
     va_list args;
     va_start(args, format);
     int retval = vstringprintf(outString, format, args);
     va_end(args);
     return retval;
    }

    // old function provided for backward-compatibility
    template<class Char, class Traits>
    inline int strprintf(std::basic_string<Char, Traits> * outString, const Char* format, ...)
    {
     va_list args;
     va_start(args, format);
     int retval = vstringprintf(*outString, format, args);
     va_end(args);
     return retval;
    }

    /* ---

    Inline Formatted Print

     string strprintf(const char* Format, ...);

    Returns :

     Formatted string


    Effects :

     Writes formatted data to a string.  formatstr() works the same as sprintf(); see your
     documentation for sprintf() for details of operation.  

    --- */

    template<class Char>
    inline std::basic_string<Char> formatstr(const Char * format, ...)
    {
     std::string outString;

     va_list args;
     va_start(args, format);
     vstringprintf(outString, format, args);
     va_end(args);
     return outString;
    }
};

File algorithmext.h (provides transform_if() function) :

/* ---

Transform
25.2.3

 template<class InputIterator, class OutputIterator, class UnaryOperation, class Predicate>
  OutputIterator transform_if(InputIterator first, InputIterator last, OutputIterator result, UnaryOperation op, Predicate pred)

 template<class InputIterator1, class InputIterator2, class OutputIterator, class BinaryOperation, class Predicate>
  OutputIterator transform_if(InputIterator first, InputIterator last, OutputIterator result, BinaryOperation binary_op, Predicate pred)

Requires: 

 T is of type EqualityComparable (20.1.1) 
 op and binary_op have no side effects

Effects :

 Assigns through every iterator i in the range [result, result + (last1-first1)) a new corresponding value equal to one of:
  1: op( *(first1 + (i - result)) 
  2: binary_op( *(first1 + (i - result), *(first2 + (i - result))

Returns :

 result + (last1 - first1)

Complexity :

 At most last1 - first1 applications of op or binary_op

--- */

template<class InputIterator, class OutputIterator, class UnaryFunction, class Predicate>
OutputIterator transform_if(InputIterator first, 
       InputIterator last, 
       OutputIterator result, 
       UnaryFunction f, 
       Predicate pred)
{
 for (; first != last; ++first)
 {
  if( pred(*first) )
   *result++ = f(*first);
 }
 return result; 
}

template<class InputIterator1, class InputIterator2, class OutputIterator, class BinaryOperation, class Predicate>
OutputIterator transform_if(InputIterator1 first1, 
       InputIterator1 last1, 
       InputIterator2 first2, 
       OutputIterator result, 
       BinaryOperation binary_op, 
       Predicate pred)
{
 for (; first1 != last1 ; ++first1, ++first2)
 {
  if( pred(*first1) )
   *result++ = binary_op(*first1,*first2);
 }
 return result;
}

Answer 8

You don't need classes, tools, or anything else. Check this out