calculating execution time in c

Question

I have written a c   program   I want to know how to calculate the time taken for execution so I won t exceed the time limit    include lt iostream gt   using namespace std   int main          int st 10000  d 10000  p 10000  n k km r t ym 10000       k 0      km 0      r 0      scanf   d   amp t       for int y 0 y lt t y              scanf   d   amp n       for int i 0 i lt n i                      cin gt  gt st i   gt  gt d i   gt  gt p i             for int i 0 i lt n i                      for int j i 1 j lt n j                                      if  d i  st i   lt  st j                                                       k p i  p j                                             if k gt km                      km k                        if km gt r          r km            ym y  r        for  int i 0 i lt t i                   cout lt  lt ym i  lt  lt endl                system  pause        return 0           this is my program and i want it to be within time limit 3 sec    how to do it   yeah sorry i meant execution time

User · Answer

I have used the technique said above  still I found that the time given in the Code Blocks IDE was more or less similar to the result obtained- may be it will differ by little micro seconds

User · Answer

Note  the question was originally about compilation time  but later it turned out that the OP really meant execution time  But maybe this answer will still be useful for someone   For Visual Studio  go to Tools   Options   Projects and Solutions   VC   Project Settings and set Build Timing option to  yes   After that the time of every build will be displayed in the Output window

User · Answer

This looks like Dijstra s algorithm  In any case  the time taken to run will depend on N  If it takes more than 3 seconds there isn t any way I can see of speeding it up  as all the calculations that it is doing need to be done   Depending on what problem you re trying to solve  there might be a faster algorithm

User · Answer

With C  11 for measuring the execution time of a piece of code  we can use the now   function   auto start   chrono  steady clock  now         Insert the code that will be timed  auto end   chrono  steady clock  now        Store the time difference between start and end auto diff   end - start    If you want to print the time difference between start and end in the above code  you could use   cout  lt  lt  chrono  duration  lt double  milli gt   diff  count    lt  lt    ms   lt  lt  endl    If you prefer to use nanoseconds  you will use   cout  lt  lt  chrono  duration  lt double  nano gt   diff  count    lt  lt    ns   lt  lt  endl    The value of the diff variable can be also truncated to an integer value  for example  if you want the result expressed as   diff sec   chrono  duration cast lt chrono  nanoseconds gt  diff   cout  lt  lt  diff sec count    lt  lt  endl    For more info click here

User · Answer

If you have cygwin installed  from it s bash shell  run your executable  say MyProgram  using the time utility  like so    usr bin time   MyProgram   This will report how long the execution of your program took -- the output would look something like the following   real    0m0 792s user    0m0 046s sys     0m0 218s   You could also manually modify your C program to instrument it using the clock   library function  like so    include  lt time h gt  int main void        clock t tStart   clock           Do your stuff here        printf  Time taken    2fs n    double  clock   - tStart  CLOCKS PER SEC       return 0

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OVERVIEW  I have written a simple semantic hack for this using  AshutoshMehraresponse  You code looks really readable this way    MACRO   include  lt time h gt    ifndef SYSOUT F  define SYSOUT F f             RPT1  0  f    VA ARGS        For Visual studio  endif   ifndef speedtest                 define speedtest   data    for  long blockTime   NULL   blockTime    NULL    blockTime   clock       NULL   false   SYSOUT F data    9fs    double   clock   - blockTime    CLOCKS PER SEC    endif   USAGE  speedtest    Block Speed              The code goes here     OUTPUT  Block Speed  0 127000000s

[c++] calculating execution time in c++

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