Tune Algorithms

In the Source window, you identified a code line in the initialize_2D_buffer hotspot function that took the most CPU time. Focus on this line and do the following:

  1. Open the code editor.

  2. Optimize the algorithm used in this code section.

Open the Code Editor

Note

Depending on the sample code version, your source line numbers may slightly differ from the numbers provided in this tutorial.

In the Source window, click the Source Editor button to open the initbuffer.cpp file in the default code editor at the hotspot line:

Hotspot line 118 is used to initialize a memory array using non-sequential memory locations. For demonstration purposes, the code lines are commented as a slower method of filling the array.

Resolve the Problem

To resolve this issue, optimize your algorithm as follows:

  1. Edit lines 110 and 113 deleting the ending forward slash (/). This action comments out code lines 111-125 marked as a "First (slower) method".

  2. Edit line 144 by adding a forward slash (/) at the end of the line. This action uncomments code lines 145-151 marked as a "Faster method".

    In this step, you interchange the for loops to initialize the code in sequential memory locations.

  3. Save the changes made in the source file.

  4. Browse to the directory you extracted the sample code (for example, /home/myuser/samples/tachyon).

  5. Rebuild your target using the make command as follows:

    $ make clean

    $ make

    The tachyon_find_hotspots application is rebuilt and stored in the tachyon directory.

  6. Run tachyon_find_hotspots as follows:

    $ ./tachyon_find_hotspots dat/balls.dat

    System runs the tachyon_find_hotspots application. Note that execution time reduced from 13.365 seconds to 10.479 seconds.

Key Terms

Hotspot

Optimization Notice

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804


Supplemental documentation specific to a particular Intel Studio may be available at <install-dir>/<studio>/documentation/.

Per informazioni complete sulle ottimizzazioni del compilatore, consultare l'Avviso sull'ottimizzazione