GPU621/Pragmatic

Pragmatic

Group Members

1. Vadym Karpenko, Research, and everything else.
2. Oleksandr Zhurbenko, Research, and everything else.

Progress

Entry on: October 17th 2016

Group page (Pragmatic) has been created and 3 suggested project topics are being considered (Preference in order specified):

1. OpenMP Debugging in Visual Studio - [MSDN Notes]
2. Analyzing False Sharing - [Herb Sutter's Article]
3. Debugging Threads in Intel Parallel Studio - [Dr Dobbs Article]

Once project topic is confirmed (On Thursday, October 20th 2016, by Professor Chris Szalwinski), group will be able to proceed with topic research.

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Entry on: November 1st 2016

Project topic has been confirmed (OpenMP Debugging in Visual Studio - [MSDN Notes]) and team is working on researching material and testing newly acquired knowledge.

Team is considering using Prefix Scan or Convolution workshops for demonstration purposes.

Notes

• All notes are based on the material outlined in "Debug Multithreaded Applications in Visual Studio" section of MSDN documentation at: https://msdn.microsoft.com/en-us/library/ms164746.aspx and other related MSDN documentation.

Entry on: November 6th 2016

Debug Multithreaded Applications in Visual Studio

While parallel processing of multiple threads increases program performance, it makes debugging task harder, since we need to track multiple threads instead of just one (Master thread). Also some potential bugs are introduced with parallel processing, for example, when race condition (When multiple processes or threads try to access same resource at the same time, for more information visit Race Condition Wiki) occurs and mutual exclusion is performed incorrectly, it may create a deadlock condition (When all threads wait for the resource and none can execute, for more info visit Deadlock Wiki), which can be very difficult to debug.

Visual Studio provides many useful tools that make multithreaded debugging task easier.

Debug Threads and Processes

A process is task or a program that is executed by operating system, while a thread is a set of instructions to be executed within a process. A process may consist of one or more threads.

Following are the tools for debugging Threads and Processes in Visual Studio:

1. Attach to Process (Dialog box) - Allows to attach the Visual Studio debugger to a process that is already running;
2. Process (Window) - Shows all processes that are currently attached to the Visual Studio debugger;
3. Threads (Window) - Allows to view and manipulate threads;
4. Parallel Stacks (Window) - Shows call stack information for all the threads in the application (Threads View);
5. Parallel Tasks (Window) - Displays all parallel tasks that are currently running as well as tasks that are scheduled for execution;
6. Parallel Watch (Window) - Allows to see and manipulate the values for one expression executed on multiple threads;
7. GPU Threads (Window) - Allows to examine and work with threads that are running on the GPU in the application that is being debugged;
8. Debug Location (Toolbar) - Allows to manipulate processes and threads while debugging the application;

Above mentioned tools can be classified as follows:

• The primary tools for working with processes are the Attach To Process dialog box, the Processes window, and the Debug Location toolbar;
• The primary tools for working with threads are the Threads window and the Debug Location toolbar.
• The primary tools for working with multithreaded applications are the Parallel Stacks, Parallel Tasks, Parallel Watch, and GPU Threads windows.