CS210 Lab: Libraries and Running Time Measurement

Prelab Questions:

Highlights of This Lab:

• Running Time Measurements
• Creating a Library and Using it

Lab Exercise:

1. Running Time Measurements

Big Oh allows us to group routines based on their projected performance under different conditions (best case, worst case, etc). Remember that Big Oh is only an estimate. It does not take into account factors specific to a particular environment, such the specific implementation, the type of computer system we are using, and the data that we are processing.

To determine how well or poorly a routine will perform in a particular environment, we need to evaluate the routine in that environment.

In "Part 1" of the laboratory exercise, you will measure the performance of three search routines:

• binarySearch()
• linearSearch()
• unknownSearch()

In summary, for the binary search, you are given a sorted array. The idea is to divide the array into two equal parts and narrow down the range of the array to be searched either to the low part of the array or high part of the array. We will continue narrowing down the range until the value is located, or until we realize that the value searched for is not in the array.

The linear search is also known as the sequential search. The idea is start with the first element, and sequentially search through the array until we find a match.

Before we can measure the performance of these routines, we must first develop a set of tools that allow us to measure the execution time.

The general approach will be the following:

• Get the current system time (startTime)
• Execute the routine
• Get the current system time (stopTime)
• Calculate the routines's execution time=stopTime-startTime

• Get the current system time (startTime)
• Execute the routine n times
• Get the current system time (stopTime)
• Calculate the routines's execution time = (stopTime-startTime)/n

• start()
• stop()
• getElapsedTime()

2. Creating a Library and Using it

2.1 Download the C++ programs

Transfer three files to your local PC (C:\Workarea). Get the files from ftp://ftp.cs.uregina.ca/pub/class/210/ftp/Library

The three files are :

This is where you should store the three files in your local PC:

    C:\Workarea

2.2 Compile the C++ programs

• create a new project called labtst
• add the three files to this project
• build and execute this project

• timer.h and timer.cpp are useful for calculating the running time measurements. Because we may want to use the class Timer over and over again, we may want to put it in a library.

2.3 What is a library?

A library is a collection of functions or classes. Unlike an object file, a library file stores each function or class, individually. When your program references a function or class contained in a library, it links that function or class and adds its code to your program. This way only functions or classes that you actually use in your program are added to the executable file.

2.4 What are header files?

Each function or class defined in the C or C++ standard library has a header file associated with it. The header files that relate to the functions that you use in your programs should be included (using #include) in your program.
There are two reasons for this:

1. to get the data types that work with many functions or classes in the standard library. Your program must have access to these data types that are defined in the header file related to each function or class
2. to obtain the prototypes for the standard library functions

2.5 Why create your own Library

Libraries can be regarded as pre-compiled functions or classes that do not need to be re-compiled if other parts of your project change. If you have a "bug-free" module (a piece of self-contained code) that could be reused with other projects, you can compile this module to a library. After you link this library to your new project, you will then be able to use any of the functions or classes in this library as if they are defined locally in your project. One major advantage is that the functions or classes in the library will not be recompiled, which saves time compiling your entire project.

In our example, "timer" is a perfect candidate: it does not contain any bugs and we can use it again in other projects.

2.6 Compile the C++ programs using a library.

In this program, timer.h and timer.cpp define and implement a time measuring class Timer. This class is independent of the kind of program it is measuring. In other words, we can reuse this Timer class to measure the running time of other programs. It naturally follows that once we make this class bug-free, we can compile it into a library.  To use this time-measuring class, we simply include the header file (i.e.timer.h) in the program and link the library to this program.

The following shows you how we do this:  

Step 1. Create the library

• Start Microsoft Visual Studio .NET
• Choose File->New->Project...
• A "New Project" Dialogue box will appear
  • Expand the "Visual C++ Projects" folder and select the "Win32" sub folder
  • From the "Templates" pane, select "Win32 Console Project"
  • Name: mylibrary
  • Location:C:\Workarea
  • Click OK
• The "Win32 Application Wizard" Dialogue box will appear (see the below picture)
  • Under Application Settings, choose Static library
  • Uncheck Precompiled header

Step 2. Add the necessary files to mylibrary and build the library

• Copy the files timer.cpp and timer.h into the mylibrary directory
• Choose Project->Add Existing Item...
• Highlight timer.cpp and timer.h
• Click Open

Step 3. Build mylibrary 

• Select Build->Build mylibrary

The following message should be displayed in the output area:

------ Build started: Project: mylibrary, Configuration: Debug Win32 ------

Compiling...
timer.cpp
Creating library...

Build log was saved at "file://C:\Workarea\mylibrary\Debug\BuildLog.htm"
mylibrary - 0 error(s), 0 warning(s)

---------------------- Done ----------------------

    Build: 1 succeeded, 0 failed, 0 skipped

The library should be stored in C:\Workarea\mylibrary\Debug

Step 4. Link the library to your project

• Choose File->New->Project...
• A "New Project" Dialogue box will appear
  • Expand the "Visual C++ Projects" folder and select the "Win32" sub folder
  • From the "Templates" pane select "Win32 Console Project"
  • Name: lab5
  • Click OK
• In the "Win32 Application Wizard" Dialogue box, select Application Settings, and check Empty project
• Copy complexity.cpp into the lab5 directory (you do not need to add timer.cpp, since you have already compiled it into a library)
• Choose Project->Add Existing Item...
• Highlight complexity.cpp , then click Open

1. Add mylibrary.lib to the Project Properties
   • From the main menu, select: Project->Properties
   • A "lab5 Property Pages" Dialogue Box should be displayed (as shown below)
   • Expand the Linker folder and select the Input subcategory
   • Click on the "Additional Dependencies" on the right-hand side and type: mylibrary.lib

   

2. Add the corresponding path (or location of this library) to the project. The path is used to locate the library files when the VC++ project is being built.
   • In the "lab5 Property Pages", under the expanded Linker folder select the General subcategory.
   • Click on the "Additional Library Directories" on the right-hand side and type: "C:\Workarea\mylibrary\Debug"
     (the location where the mylibrary.lib can be found)

   

3. Add the path where the timer.h file is to be found.
   • Again, in the "lab5 Property Pages" dialog, expand the C/C++ folder.
   • Select the subcategory General and click on "Additional Include Directories".
   • Type in: "C:\Workarea\mylibrary\"

   

------ Build started: Project: lab5, Configuration: Debug Win32 ------

Compiling...
complexity.cpp
Linking...

Build log was saved at "file://c:\Workarea\lab5\Debug\BuildLog.htm"
lab5 - 0 error(s), 0 warning(s)

---------------------- Done ----------------------

    Build: 1 succeeded, 0 failed, 0 skipped

Finally, click on Debug->Start Without Debugging to run your program.
Your output should look like the following:

3. Lab Exercise

• Get the files:

  Click here
  To get the zipped files for this exercise 
  

• Extract all of the files to the WORKAREA. There are three files used in this program:
  • search.cpp contains the implementation of a set of searching routines.
  • sort.cpp contains the implementation of a set of sorting routines (used to sort the array so that binary search will work).
  • timesrch.cpp -- the main program. Outputs the runtime of the three searching routines.

  Your primary tasks for this exercise are:

  1. Create a normal C++ Win32 Console Project using the three files.
  2. Include the timer library into this program.
  3. Compare the execution times of the three searching routines.

  Steps include:

• Adjust the project properties to link to "mylibrary".
  Don't forget the three steps:
  1. Add mylibray.lib to the "Additional Dependencies"
  2. Tell it where to find the mylibrary.lib
     (The setting is in the Property Pages, under Linker->General)
  3. Tell it where to find the timer.h file
     (The setting is in the Property Pages, under C/C++->General)

• Compile and run the project. You will notice that the values are printed in the following format:

  Enter the number of keys : 1000
  
  
       Sort     | Number of |  Total Time  |   Time  per
       Type     |   Sorts   |     (s)      |    Sort(s)
  --------------|-----------|--------------|--------------
  Selection sort|       1700|    3.093e+000|    1.819e-003
  QuickSort     |      14000|    2.922e+000|    2.087e-004
  unknown sort  |        500|    2.781e+000|    5.562e-003
  Press any key to continue
  

  The 2.087e-004 is equivalent to 2.087*10^-4 or 0.000002087.

• Fill in the handout provided by your instructor.
  This involves plotting the time that it takes to run the three algorithms with different numbers of keys. In the end, you will have three lines for the three searches: linear, binary, and unknown.

  Suggestion: The increments for the "Search time" axis have been left up to you. First, write everthing as 10^-6 seconds. Then, create six tick marks along the y-axis: 3, 6, 9, 12, 15, and 18.

Part 2

• Get the files:

  Click here
  To get the zipped files for this exercise 
  

• Extract all of the files to the WORKAREA. There are two files used in this program:
  • sort.cpp contains the implementation of a set of sorting routines (including selectionSort(), quickSort(), and unknownSort())
  • timesort.cpp -- the main program. Outputs the runtime of the three sorting routines.

  Your primary tasks for this exercise are:

  1. Create a normal C++ Win32 Console Project using the two files.
  2. Include the timer library into this program.
  3. Compare the execution times of the three sorting routines.

• Follow the steps outlined in Part 1 and complete the handout provided by your instructor.

  Suggestion: The increments for the "Search time" axis have been left up to you. First, write everthing as 10^-3 seconds. Then, create ten tick marks along the y-axis: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100.

4. Postlab Exercises

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