Vectorization Essentials, Vectorization and Optimization Reports
This chapter describes how to run and interpret Intel® C/C++ Compiler and Intel® Fortran Compiler vectorization and optimization reports. These reports can pinpoint areas where the compiler is not adding vectorization or able to introduce optimizations. It may be possible to modify your code or communicate additional information to the compiler to vectorization or optimizations to be applied to the generated code for your application.
Note: With version 15.0, the four optimization report options (-opt-report, -vec-report, -openmp-report, and -par-report) have been consolidated under a single -qopt-report interface. This consolidated optimization report has been rewritten to improve the presentation, content, and precision of the information provided so that users better understand what optimizations were performed by the compiler and how they may be tuned to yield the best performance. The output of this report no longer defaults to stderr due to issues with parallel builds. Instead, by default an output file (extension .optrpt) containing the report for each corresponding object file is generated to the target directory of the compilation process (i.e. the same directory where object files would be generated). The option -qopt-report-file (for example: -qopt-report-file:stderr) can be used to change this behavior.
The -vec-report, -openmp-report, and -par-report options have been deprecated, but they remain and map to corresponding values of the -qopt-report option. However, the report information and formatting, and the default to reporting to a file, will follow the new -qopt-report model. It is strongly recommended that you read the documentation for full details. See the Intel Compiler User’s Guide under Compiler Reference->Compiler Option Categories and Descriptions->Optimization Report Options.
You should now know how to run vectorization and optimization reports to determine areas where vectorization could be enabled or optimization improved by the compiler with changes to your source code.
It is essential that you read this guide from start to finish using the built-in hyperlinks to guide you along a path to a successful port and tuning of your application(s) on Intel® Xeon Phi™ architecture. The paths provided in this guide reflect the steps necessary to get best possible application performance.