Changes

The Intel C++ Compiler is not the only tool that comes provides with IPS XE 2019. It also includes next applicationstools to do thread debugging:  [[File:XEVTuneLogo.jpg]]

[[File:Inspector VS.PNG| 700px]]

[[File:Inspector_app.PNG| 200px]] 

[[File:Inspector_03_Threading_analysis_startpage.PNG| 700px]]

[[File:Inspector_03_Threading_analysis_CollectionLog.PNG| 300px]]

 There is a thread and timeline information for all code locations in one or all occurrences of the problem(s) highlighted in the Problems pane [[File:Inspector_03_Threading_analysis_02_dataRace_.PNG| 1000px]]

[[File:Inspector_03_Threading_analysis_02_dataRace_source_.PNG| 1000px]]

==='''IntroductionAbout VTune'''===

Intel VTune amplifier is a analysis software that allows you the ability to measure performance of your serial or multithreaded program. VTune allows you to analyze the performance of your algorithms and multithreading. It can help with debugging threads by calculating overhead, finding bottlenecks or inefficiencies.

==='''Create VTune allows you to analyze the performance of your algorithms and multithreading. It can help with debugging threads by calculating overhead, finding bottlenecks or inefficiencies.  VTune can be ran as a project'''===stand alone program or Integrated with Visual Studio.

==='''Configure a projectStarting VTune'''===

 Select the '''Select configure Analysis.'''option.

The following screen will To see the different analysis's available to be displayedran with Vtune. Click on the three little dots circled in the below picture. To expand more options for running VTune.

[[File:startup optionsThis menu will appear, it contains different tests that you can run against your program.PNG | 600px]]

[[File:startup options.PNG | 400px]]  ==='''How it worksDemo'''===On  The following is some code from the main page Matrix Multiplication exercise we can did in lab3. It contains 2 versions of the “matMul” function.  Change the value of the version macro inside "MatMul.cpp" to run the different versions. *Version 1 – the matrix multiplication logic has been put inside a parallel for statement *Version 2 – the matrix multiplication logic is still inside the parallel for statement, but it is being dynamically scheduled and certain variables are selected to be private or shared.  '''[https://github.com/coreyjjames/CoreyJJames/tree/Lab3_VTune_Example Example Code]'''  To run the testexample code, by clicking on copy the code into Visual Studio and Build it. - Run the program with VTune threading analysis. - The point of interest in the program is under the blue play buttonplatform tab.

[[File:start test- You will notice in version 1 some of the threads finish before other's. The work is not being spread evenly.PNG | 600px]]

When - In version 2, that issue is resolved all the test completes, threads end at the summary page will be displayedsame time. This will outline the results from the testWhen I ran Version 2 I saw around a 0.6s increase in performance.

[[FileImportant notes:test complete*Run in Release X64, using OpenMP and Intel compiler.*Turn off optimization so you can see source code Hotspot's*Rebuild after any changes.PNG | 600px]]

**Elapsed Time: this is the amount of time your program took to run***The CPU time: displays the effective, spin and overhead times.**Top Hotspots: Displays the area’s that were most active in your program.**Effective CPU Utilization Histogram: This shows the time your program spent using x number of threads. The graph shows x axis is the moments that your program was a certain number of threads. And the y axis is the time that your program used that number of threads for.**Collection and Platform Info: this display’s all the hardware Display's relevant information about the computer the test was run on.analysis

Lets start by creating a project on Visual Studio, I am using a sample code from Intel Advisor folder which they provide different samples for you to test the functionality of it. They can be found under <Your-Installed-Directory>\IntelSWTools\Advisor 2019\samples\en. I am using the "nqueens_Advisor" one. After choosing your project build the solution and look the following Icon from the image below

'''First step is to Collect the Survey Target report by clicking "Collect"''' 

 '''3 -''' It is a dropdown list which shows you all the threads runned in this program which it is important for in this case since we are focusing on debugging threads  '''Second step is running Check Dependecies'''For running Check Dependecies we should select one of the function call or loop from the first step from the following window  [[File:Drop.png|800px]]  Pay attention to the black water drop which indicates me that I have selected a loop or function for Annotation. This means that part of the code will be inside of an Annotation range specially for the analysis. This is a new feature since before it did not exist and we would have to go into the source code and add the Annotation range for the part of the code which we would like to analyze.  After selecting the loop or function for Annotation we will proceed to start the Check Dependecies  [[File:Dependency.png|200px]]  Starting Check Dependencies will take a bit longer than running the program so be patient with it. After it is done the following window should appear.  [[File:No_lock.png|900px]]  '''1 -''' It displays the selected loop or function for Annotation and tells us the number of errors it contains. '''2 -''' Here is a very important window since it tells us in detail all the errors that needs to be fixed. '''3 -''' In this case I selected the P6 error and it tells me in which function it is in and the specific variable affected.  ==='''Fixing the problem'''===We have Identified that there are several problems from the Check Dependencies report lets try to fix one of them. From the "Dependecies Report - Problem and Messages" Window. right-click any data row and choose Edit Source to open the source file. It will bring you directly to the code of the selected problem. In my case I selected the previously selected error P6 and the error is because multiple tasks may try and increment nrOfSolutions at the same time. So by adding Lock into it can avoid the multiple access to the variable making it one by one with the following way.  [[File:Lock.png|300px]]  After adding the lock, we build the solution again and re run the 2 analysis following the previous steps. This time we can notice that our Check Dependencies Report has changed  [[File:Refined.png|800px]]  The previous error has disappeared. Notice that previously there were 2 errors in RAW and now there is just one. We can also verify from the "Dependecies Report - Problem and Messages" Window that the previous problem is not there anymore which means it has been fixed.