OptView

Overview

The introduction of the Intel IA-64 Itanium processor brings a substantial increase in potential speed for applications that are tuned to run on this architecture. At the same time, the role of the compiler has become increasingly important in realizing the full potential of the processor (some would say "critical").

To achieve performance commensurate with the capabilities of the IA-64 processor, developers must be aware of those portions of their source code that were successfully optimized by the compiler and others that might need further attention. This requires that information revealed by the compiler during optimization phases is readily available. Unfortunately, this information is often not easily found or can sometimes be difficult to comprehend.

OptView is a tool that's designed to make it easier for developers and performance analysts to navigate through the frequently lengthy output contained in optimization reports produced by Intel compilers for the Itanium processor. OptView provides an easy-to-use and intuitive interface that allows the user to browse through their own source code which is automatically cross-referenced by the tool with the optimization reports.

OptView is one of the PerfSuite tools designed to assist with software performance analysis. OptView can be used on both Microsoft Windows and X-Windows.

Generating Optimization Reports

To generate an optimization report with the Intel 6.0 compilers that can be used by OptView, compile the source file as usual but include the flag -opt_report_file filename. The report will be written to the file filename.

Tip: If you have a lot of source files to process all at once, and you use a Makefile to compile, you can also use make's "suffix" rules to have optimization reports produced automatically, each with a unique name. For example,

	.f.o:
		efc -c -o $@ $(FFLAGS) -opt_report_file $*.opt $*.f
The above will create optimization reports that are named identically to the original Fortran source but with the suffix ".f" replaced by ".opt". You can then start working with these files using OptView.



Using OptView at NCSA

OptView is installed on NCSA's Itanium cluster (Titan) in the directory /usr/apps/tools/bin. You can either add that directory to your UNIX PATH or you can invoke optview using an absolute path name. You'll need to be using the X-Window system and to have set your DISPLAY environment variable correctly for OptView to work.

Example

Here's a snapshot of the main window of OptView. An optimization report has been loaded into the tool and a portion of the summary information is shown:

OptView main window
The OptView main window, showing a portion of the molecular dynamics application
NAMD2 (Klaus Schulten/Theoretical Biophysics Group, University of Illinois).

As you can see, OptView presents optimization information organized in a manner that's easily understood and navigated. The screen above shows:

Examining Source Code & Specific Loops

Additional displays available in OptView feature color-highlighted browsing of the original source code as well as pop-up windows that provide in-depth summaries of the success of individual optimizations (or failure to optimize, which is probably of more interest to the developer concerned about optimization).

After you've loaded an optimization report into OptView, you can access the source code browser for a particular file by double-clicking on the file name from within the "Source" frame in the main OptView window.

For example, here's a screen shot of an OptView source code browser displaying a portion of a program in which a loop was successfully optimized. The loop control statement is highlighted by a light green background (if the compiler had failed to optimize the loop, the statement would still have been highlighted, but in red). The color-coding of optimizations provides very quick insight into the overall success of the compiler when translating your source code.

OptView source code browser
An OptView source code browser window, showing a portion of a kernel from the
computational fluid dynamics application GenIDLEST (Danesh Tafti, Virginia Tech)



The highlighted regions are also "active hyperlinks" that enable you to drill down and examine more detailed information about the optimizations applied to specific loops (or the reasons why optimization failed). You can request this additional information by clicking on the highlighted source code line (this feature is not shown here).

Browsing Multiple Optimization Reports Simultaneously

OptView also allows you to browse multiple files in a given directory, which can help give a quick overall view of which source files were highly-optimized and which might need additional work. Here's an example of this feature:

OptView multiple-report display
An OptView source directory browser window, showing a summary of
the software pipeline optimizations in the source of the
machine learning program CN2 (Peter Clark, Univ. of Texas/Boeing Corp.)


This source directory browser window provides easy access to any of the individual optimization reports by clicking on the optimization report file name in the leftmost column. This will automatically load that report in the main OptView window where you can examine that report further.

Summary

OptView and similar tools can be major time-savers that are invaluable when working with large applications containing many different source files (especially if you're not familiar with the application). By providing a very quick method of isolating which files or portions thereof are especially difficult for the compiler to deal with, OptView helps you to quickly focus your attention on those areas that need it the most.

We're continuing to investigate ways in which performance- and optimization-related information and measurements can be made much more easily accessible.

For more information

Those who are interested in the details of software pipelining in the compiler can refer to the report Iterative Modulo Scheduling, B. R. Rau, 1995. (H P Labs Technical Report HPL-94-115)

More general information about the design and features of the Intel IA-64 compiler can be found in An Overview of the IA-64 Compiler, Dulong et al, 1999. (Intel Technology Journal, 4Q 1999). Note: if you have trouble loading this article, you may want to search for the title directly from http://developer.intel.com/.

Specific optimization information from Intel is also available in the document Optimizing Applications with the Intel (R) C++ and Fortran Compilers for Windows and Linux.


Last modified: Sunday, 08-Feb-2004 14:45:25 CST

PerfSuite
National Center for Supercomputing Applications
University of Illinois at Urbana-Champaign