Managing Threading Errors with Intel? Parallel Inspector XE
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Copyright ? 2010, Intel Corporation. All Rights Reserved.Table of Contents
Disclaimer ii
Parallelism Tools – Checking for Thread Correctness 1
Activity 1 - Choose, Build and Run a project 1
Activity 2 - Configure and Run Analysis 9
Activity 3 - Manage result data after analysis 13
Activity 4 - Resolve, Rebuild and Rerun 21
Parallelism Tools – Checking for Thread Correctness
Activity 1 – Choose, Build and Run a Project
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Time Required |
Ten minutes |
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Objective |
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The application is a 2-D ray tracer/renderer called tachyon written in C++. The code is small enough that you may be able to identify potential memory access violations by visual inspection. If you identify and make a list of problems, check your list with the list that Parallel Inspector XE identifies.
Choose a project
- With Windows Explorer*, locate the samples folder in the Parallel Inspector XE directory.
- From the Microsoft Visual Studio* menu, choose File > Open > Project/Solution.
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In the Open Project dialog box, open the filesamples\windows\tachyon_insp_xe\vc8\tachyon_insp_xe.sln fileby double-clicking it.
This should now display tachyon_insp_xe solution in the Solution Explorer.
- In the Solution Explorer, right-click the find_and_fix_threading_errors project and choose Set as Startup Project from among the menu options.
Build a project
- We first need to verify debug mode is configured to produce the best results. So in the Solution Explorer, right-click the find_and_fix_threading_errors project and choose Properties to display the Property Pages dialog box.
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Verify the Configuration drop-down list is set to Debug or Active(Debug).
- In the left pane, choose Configuration Properties > C/C++ > General.
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Verify the Debug Information Format is set to Program Database (/Zi) or Program Database for Edit & Continue (/ZI).
- In the left pane, choose Configuration Properties > C/C++ > Optimization.
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Verify the Optimization field is set to Disabled (/Od).
- In the left pane, choose Configuration Properties > C/C++ > Code Generation.
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Verify the Runtime Library field is set to Multi-threaded DLL (/MD) or Multi-threaded Debug DLL (/MDd).
- In the left pane, choose Configuration Properties > Linker > Debugging.
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Verify the Generate Debug Info field is set to Yes (/DEBUG).
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Verify the project is set to build in debug mode. Click the Configuration Manager button and verify the Active solution configuration drop-down list is set to Debug.
- Click the Close button to close the Configuration Manager dialog box.
- Click the OK button to close the Property Pages dialog box.
Run a project
- From the Visual Studio* menu, choose Debug > Start Without Debugging.
- When the Visual Studio* IDE responds this project is out of date, click Yes to build the project.
- The application is run but the application output window will be empty and grey because of memory errors in the code!
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You verified the find_and_fix_threading_errors project is set to produce the most accurate, complete results, compiled and linked the project and ensured the resulting find_and_fix_threading_errors.exe file runs on your system outside the Inspector XE.
Activity 2 – Configure and Run analysis
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Time Required |
Ten minutes |
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Objective |
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Configure a threading error analysis
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From the Visual Studio* menu, choose Tools > Intel Inspector XE 2011 > New Analysis to display an Analysis Type window similar to the following:
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Open the Threading Error Analysis folder and choose the Detect Deadlocks and Data Races analysis type to display a window similar to the following. (If necessary, click the
icon in the Details region to display analysis type characteristics.)
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Use the Navigation toolbar to navigate among Inspector XE windows. The buttons on the toolbar vary depending on the displayed window. |
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The Analysis Types region shows available preset analysis types. You can also use existing analysis types as templates to create custom analysis types. |
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Use the checkbox(es) and drop-down field(s) to fine-tune some, but not all, analysis type characteristics. If you need to fine-tune more analysis type characteristics, choose another preset analysis type or create a custom analysis type. |
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The Details region shows all current analysis type characteristics. Try choosing a different preset analysis type or checkbox/drop-down list value to see the impact on the Details region. |
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Use the Command toolbar to control analysis runs and perform other functions. For example, use the Project Properties button to redisplay the Project Properties dialog box. |
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After you finish experimenting, ensure your Analysis Type window resembles the following window:
- You chose a preset analysis type of intermediate scope to detect memory errors in the find_and_fix_memory_errors.exe file.
Run a threading error analysis
- Click the Analyze button on the Analysis Type window to:
- Execute the find_and_fix_threading_errors.exe file.
- Identify memory errors that may need handling.
- Collect the result in a folder in the tachyon_insp_xe\vc8\My Inspector XE 2011 Project - find_and_fix_threading_errors folder.
- Finalize the result (convert symbol information into filenames and line numbers, perform duplicate elimination, and form problem sets).
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During collection, the Inspector XE displays a Collection Log window similar to the following:
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The Visual Studio* IDE offers a pointer to the result from the Solution Explorer to provide easy future access. Here, the Visual Studio* IDE created a MyInspector XE Results/find_and_fix_threading_errors folder in the Solution Explorer. Open it to see the pointer to the r000ti2 result. |
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The result name appears in the tab. Here, the name of the result (and the name of the result folder in the tachyon_insp_xe\vc8\My Inspector XE 2011 Project - find_and_fix_threading_errors folder) is r000mi2, where
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The Collection Log pane shows detected problems in real time. This tutorial does not cover examining and solving problems during collection. For more details, please check the Inspector XE Help Index for examine result during analysis. |
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The Collector Messages pane shows analysis status messages. You can control where application output appears: Separate console window (as in this tutorial), Application Output pane in the Collection Log window, or Visual Studio* output window. |
Activity 3 – Manage result data after analysis
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Time Required |
Fifteen minutes |
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Objective |
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After analysis (both collection and finalization) completes successfully, the Inspector XE displays the Summary window:
Choose Problem Set
Start exploring a threading error.
Interpret the Summary window
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The Summary window is the starting point for managing result data. It groups observations into problem sets, and then prioritizes the problem sets by severity and size.
Notice the arrow to the left of the Analysis Type button. Use it to revisit a read-only window showing your target project properties. |
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Think of the Problem Sets pane as a to-do list. Start at the top and work your way down. |
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The Observations in Problem Set pane shows all the observations in all the problems in the selected problem set. By default, the Inspector XE selects the first problem set for you.
Here, the Inspector XE selected the Invalid Memory Access problem set, which contains one problem composed of a Write observation. |
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This tutorial does not cover manipulating the timeline. For more details, check the Inspector XE Help Index for manipulate timeline. |
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The Summaries/Subsets pane categorizes all displayed problem sets by specific criteria. Use it to temporarily limit the list in the Problem Sets pane to only those problem sets that meet specific criteria. This tutorial does not cover searching for specific problem sets. For more details, check the Inspector XE Help Index for select/problem set search criteria. |
Choose a problem set
Click the data row for the Data race problem set in the find_and_fix_threading_errors.cpp source file to display a window similar to the following:
This Data race problem set contains one or more problems composed of Read and Write observations.
Choose a focus observation
Double-click the data row for the X2 Write observation to display the Sources window, which provides more visibility into the error:
Interpret Result Data
In this section, we will see how to determine the cause of the detected threading error.
To interpret the Sources window:
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Like the pane on the Summary window, the Observations in Problem Set pane shows all the observations in one Write -> Write Data race problem and three Write -> Read Data race problems in the Data race problem set. There are at least two observations in each problem. The X2 Write observation is in all problems.
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The Related Observation
Code pane shows the source code in the
find_and_fix_threading_errors.cpp source file surrounding the X3
Read observation. (Notice the |
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The Focus Observation
Code pane shows the source code in the
find_and_fix_threading_errors.cpp source file surrounding the X2
Write observation. (Notice the |
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This tutorial does not cover manipulating the timeline. For more details, check the Inspector XE Help Index for manipulate timeline |
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To interpret window icons:
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Icon |
Meaning |
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This observation is the focus observation. The Inspector XE chose it for you when you double-clicked the Mismatched allocation/deallocation problem set on the Summary window. Its source code is currently displayed in the Focus Observation Code pane. |
Observation source code is available for viewing in the Inspector XE and editing in the Visual Studio* editor. |
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This observation is related to the focus observation. Its source code is currently displayed in the Related Observation Code pane. |
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To view source code for another observation:
Double click the data row for the X4 Read observation in the Observations in Problem Set pane to display a window similar to the following:
Notice the window changes:
- The Related Observation Code pane now shows the source code for the X4 Read observation.
- The
icon for the X4 Read observation is now
instead of
in the Observations in Problem Set pane (and throughout the Sources window).
Understand the issue:
A Write -> Write Data race problem occurs when multiple threads write to the same memory location without proper synchronization. A Write -> Read Data race problem occurs when one thread writes to, while a different thread concurrently reads from, the same memory location.
The commenting in the Focus Observation Code window identifies the cause of the Data race problems: Multiple threads are concurrently accessing the global variable col. One possible correction strategy: change the global variable to a local variable.
Access more information on interpreting and resolving problems:
- Right-click any observation in the Observations in Problem Set pane.
- Choose Explain Problem to display Inspector XE Help information for the Data race problem type.
Activity 4 – Resolve, Rebuild and Rerun
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Time Required |
Twenty minutes |
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Objective |
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Resolve an issue:
- Scroll to this source code near line 80 in the Focus Observation Code pane: color col;
- Double-click the line to open the find_and_fix_threading_errors.cpp source file in a separate tab where you can edit it with the Visual Studio* editor:
- Comment color col; and uncomment //color col; near line 89:
- Click the r000ti2 tab to redisplay the Sources window:
Rebuild and Rerun Analysis
To see if your edits resolved the memory errors:
- Rebuild the project with your edited source code.
- Run another analysis.
- Start managing result data after collection.
To rebuild the project:
- Right-click the find_and_fix_threading_errors project in the Solution Explorer.
- Choose Build.
To run another analysis:
From the Visual Studio* menu, choose Tools > Intel Inspector XE 2011 > Analyze As... > Threading Error Analysis / Detect Deadlocks and Data Races to run another analysis of the same analysis type:
Notice the image now displays.
To start managing result data after collection:
After analysis (both collection and finalization) completes successfully, the Inspector XE displays the Summary window:
Notice the Inspector XE:
- Created a new result tab.
- No longer detects problems in the find_and_fix_threading_errors.cpp file