Intel® Advisor User Guide

User Guide

Contents

Suitability Report Overview

After the Suitability tool runs your program's target executable to collect data, the
Suitability Report
 window appears. It displays the approximate predicted performance based on its analysis of the annotated parallel sites and tasks.
Example of a Suitability Report when Target System is CPU
This screen shows data based on a
Target System
 of
CPU
. The screen shown on your system will differ.
The upper-left area shows the
Maximum Program Gain for All Sites
 in the program. Your overall goal of adding parallelism is to increase the
Maximum Program Gain for All Sites
 so the parallel program will execute as fast as possible. The measured serial execution runtime, predicted parallel runtime, and any measured are displayed below
Maximum Program Gain for All Sites
. Use the predicted Suitability gain values to help you make informed decisions about where to add parallelism.
If the Suitability tool detects any annotation-related errors, they appear at the top of the
Suitability Report
 window. If you see this type of error, the displayed Suitability data may not be reliable. Annotation-related errors may be caused when the correct sequence of annotations do not occur because of missing annotations, when unexpected execution paths occur, or if Suitability data collection was paused while the target was executing.
Use the upper-right row of to model performance. Choose a hardware configuration and threading model (parallel framework) values from the drop-down lists. If you select a
Target System
 for
Intel® Xeon Phi™
 processors, an additional value for total
Coprocessor Threads
 appears.
Below this row is a grid of data that shows the estimated performance of each parallel site detected during program execution. The
Site Label
 shows the argument to the site annotation. Examine the predicted
Site Gain
 and
Impact to Program Gain
 (higher values are better) to estimate how much each site contributes to the
Maximum Program Gain for All Sites
 for all sites (described above). To expand the data under
Combined Site Metrics
 or
Site Instance Metrics
, click the icon to the right of that heading; to collapse data, click to the right of that heading.
To view source code for a selected parallel site, click its row to display the
Suitability Source
 window.
To show or hide the side command toolbar, click the Show side command toolbar or Hide side command toolbar icon.
The
Scalability of Maximum Site Gain
 graph summarizes performance for the selected site. The number of CPU processors or total number of coprocessor threads appears on the horizontal X axis and the target's predicted performance gain appears on the Y axis. To change the default
CPU Count
 and the
Maximum CPU Count
, set the Options value.
If you choose a
Target System
 of
CPU
, to view detailed characteristics of the selected site as well as its tasks and locks, click the
Site Details
 tab.
Use the
Loop Iterations (Tasks) Modeling
 (or
Tasks Modeling
) to experiment with different loop structures, iteration counts, and instance durations that might improve the predicted parallel performance.
For example, you might want to see the impact of modifying your nested change loop structure, modify the loop body code, or change number of iterations.
If the task annotations indicate likely task parallelism, the title will appear as
Task Modeling
 (instead of
Loop Iterations (Task) Modeling
 for data parallelism).
Use the
Runtime Modeling
 to learn which parallel overhead categories might have an impact on parallel overhead. If you agree to address a category later by using the chosen parallel framework's capabilities or by tuning the parallel code after you have implemented parallelism, check that category.
If the chosen
Target System
 is
Intel Xeon Phi
 or
Offload to Intel Xeon Phi
, additional options appear below the
Runtime Modeling
 area. To expand this area, click the down arrow to the right of
Intel Xeon Phi Advanced Modeling
.
Below the graph is a list of issues that might be preventing better
predicted
 performance gains as well as a summary of serial and predicted parallel time. To expand a line, click the down arrow to the right of the item's name. Most issues are related to the
Runtime Modeling
. Later, you can use other Analyzer tools like to measure
actual
 performance of your parallel program.

Target System Hardware Configurations

The
Target System
 lets you select the type of hardware configuration to be analyzed. From this drop-down list, you can check each type to learn the likely predicted performance characteristics for each:
  • CPU
     shows the predicted performance of only the CPU. Choose this item for
    Intel® Xeon®
    or similar processors that do not have significant
    parallel coprocessors
    . For an
    Intel® Xeon Phi™
     processor, choose this setting to only model the host processor, such as an
    Intel Xeon
    processor. If you choose this configuration, you can specify the
    CPU Count
     modeling parameter.
  • Intel Xeon Phi
     shows the predicted performance when using only the
    Intel Xeon Phi
     coprocessor cores, and not the host processor. This parameter does not account for data exchange amongst
    Intel Xeon Phi
     coprocessor cores and the host CPU. If you choose this configuration, you can specify the
    Coprocessor Threads
     modeling parameter.
  • Offload to Intel Xeon Phi
    shows the predicted performance when using
    Intel Xeon Phi
     coprocessor manycores to execute parallel code after the host CPU starts the program and before execution resumes on the host CPU for program completion. If you choose this configuration, you can specify the
    Coprocessor Threads
     and
    CPU Count
     modeling parameters.

Data Displayed When the Target System is
Intel® Xeon Phi™

A sample screen below shows changes in orange boxes when the
Target System
 is
Intel Xeon Phi
 (instead of
CPU
).
Suitability Report when Target System is Intel Xeon Phi
  • The displayed data changes, such as the
    Maximum Program Gain for All Sites
     and the serial and predicted parallel time.
  • The graph's appearance changes to a gray-green color and the X axis displays
    Coprocesser Threads
     (instead of
    CPU Count
    ) to represent the predicted performance of the manycore parallel coprocessor. This graph shows the predicted parallel performance of the manycore parallel coprocessor without accounting for data exchange amongst
    Intel Xeon Phi
    i coprocessor cores and the host CPU. For many applications, the number of task instances does not scale enough to fully utilize the many cores of the parallel coprocessor, as indicated by a hover tip. Applications that are not appropriate for a
    Intel Xeon Phi
     processing system have values that appears in the gray part of the graph; in this case, try modeling other types of the
    Target System
    .
  • The lines between the graph's gray and green areas is a reference baseline, where the reference CPU chosen to calculate the
    Intel Xeon
    processor peak baseline is a dual-socket 8-core
    Intel Xeon
    processor E5-26xx product family (2.7 GHz, 16 cores total). When the
    Maximum Site Gain
     exceeds this baseline, you might consider using an
    Intel Xeon Phi
     coprocessor rather than an
    Intel Xeon
    or similar processor.
    When the
    Target System
     is either
    Intel Xeon Phi
     or
    Offload to Intel Xeon Phi
    , the
    Intel Xeon Phi Advanced Modeling
     options appear. See
    Intel® Xeon Phi™
     Advanced Modeling    .

Data and Modeling Parameters When the Target System is Offload to
Intel Xeon Phi

A sample screen below shows changes in orange boxes when the
Target System
 is
Offload to Intel Xeon Phi
 (instead of
CPU
) and the
Offload to Intel Xeon Phi
 column is selected.
Suitability Report when Target System is Offload to Intel Xeon Phi
When you select a
Target System
 of
Offload to Intel Xeon Phi
 coprocessor:
  • The displayed data changes, such as the
    Maximum Program Gain for All Sites
     and the serial and predicted parallel time.
  • An additional modeling parameter appears as a new column for each site named
    Offload to Intel Xeon Phi
    . If selected, the
    Scalability of Maximum Site Gain
     graph displays
    Coprocessor Threads
     on the X axis. If unselected, the graph displays
    CPU Count
     on the X axis.
  • In the upper-right corner, an additional modeling parameter appears. That is, both the total number of
    Coprocessor Threads
     and the
    CPU Count
     appear because both the number of CPUs and the coprocessor's total number of hardware threads should be considered to predict parallel execution.
  • Additional modeling parameters appear below
    Runtime Modeling
     area under
    Intel Xeon Phi Advanced Modeling
     - see
    Intel® Xeon Phi™
     Advanced Modeling    .
  • When the column named
    Offload to Intel Xeon Phi
     is selected, the graph's appearance changes to a gray-green color and the X axis displays
    Coprocessor Threads
     instead of
    CPU Count
    . This graph shows the predicted performance of the manycore parallel coprocessor and its host CPUs. For many applications, the number of task instances does not scale enough to fully utilize the many cores of the parallel coprocessor, as indicated by a hover tip. Applications that are not appropriate for an
    Intel Xeon Phi
     processing system have values that appear in the gray part of the graph; in this case, try modeling other types of the
    Target System
    . Applications that are appropriate for offload to an
    Intel Xeon Phi
     processing system have values that appear in the green part of the graph.
    The lines between the graph's gray and green areas is a reference baseline, where the reference CPU chosen to calculate the
    Intel Xeon
    processor peak baseline is a dual-socket 8-core
    Intel Xeon
    processor E5-26xx product family (2.7 GHz, 16 cores total). When the
    Maximum Site Gain
     exceeds this baseline, you might consider using an
    Intel Xeon Phi
     coprocessor rather than an
    Intel Xeon
    or similar processor.

Site Details Tab

If you chose a
Target System
 of
CPU
, after you click the
Site Details
 tab (next to
Site Performance Scalability
), the lower part of the Suitability Report shows details about the selected site, as well as details about each task and lock within that site.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.