User Guide

  • 2020
  • 06/18/2020
  • Public Content
Contents

Suitability Report, Scalability Graph

View a scalability graph showing the predicted approximate performance characteristics of the selected site. The Scalability graph is automatically updated if you change modeling assumptions in the Suitability Report.
Two types of graphs appear depending upon the selected
Target System
. The X axis of the graph shows either
CPU Count
to model CPU usage or
Coprocessor Threads
to model
Intel® Xeon Phi™
coprocessor usage.

Scalability Graph for CPU Count Usage

If you select a
Target System
of
CPU
or select
Offload to Intel Xeon Phi
and uncheck the column
Offload to Intel Xeon Phi
for the selected site, a green-yellow-red graph appears and the X axis shows
CPU Count
.
The number of CPUs appears on the X axis and the program's predicted run-time performance gain appears on the Y axis.
Near the top of each vertical line for a CPU number, you will see a box and a circle that indicate the minimum and maximum predicted gain values. The color shading indicates the likely benefit. For example, if the minimum-maximum range appears in the red-shaded area, this site is hurting your program's performance and you should significantly modify or remove the site annotations.
If the minimum-maximum range appears in the:
  • Red-shaded area, this site is hurting your program's performance. Remove or significantly modify the site annotations.
  • Yellow-shaded area, this site is helping your program's performance, but maybe the gain may not be enough to justify the effort you needed to refactor and maintain your program. You should investigate how the results can be improved. Also, it might be more energy (power) efficient to increase the serial throughput using program changes or faster processors (parallel machines are designed to run at a lower clock frequency than certain serial machines).
  • Green-shaded area, this indicates good results. If you can achieve this level of performance, you will likely have a significant improvement to your program. The green area also indicates energy efficient (power) parallel speedups.
If the minimum-maximum range forms a flat line, this indicates that the maximum number of CPUs specified exceeds the number of task instances.

Scalability Graph for
Intel® Xeon Phi™
Coprocessor Threads Usage

If you select a
Target System
of
Intel Xeon Phi
or select
Offload to Intel Xeon Phi
and check the column
Offload to Intel Xeon Phi
for the selected site, a gray-green graph appears.
The X axis shows
Coprocessor Threads
and the program's predicted run-time performance gain appears on the Y axis.
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.
Near the top of each vertical line for
Coprocessor Threads
, you will see a box and a circle that indicate the minimum and maximum predicted gain values. The color shading indicates the likely benefit depending on whether the number of predicted threads would saturate the manycore coprocessor.
This graph shows the predicted parallel performance of the manycore parallel coprocessor without accounting for data exchange amongst
Intel Xeon Phi
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 appear in the gray part of the graph; in this case, try modeling other types of the
Target System
.

For Each Site, Decide Whether to Modify or Keep Annotations

Use the
Suitability Report
window to view the predicted parallel performance of each parallel site and its impact on the
Maximum Program Gain for All Sites
. For example, if a site either has a
Site Gain
of less than 1.0 or does not contribute to
Maximum Program Gain for All Sites
, modify or remove its annotations. In contrast, any site that contributes to
Maximum Program Gain for All Sites
should be kept. For most sites, carefully examine the annotations, overhead assumptions, and related code.
Within the upper-right area of the
Suitability Report
window, if multiple parallel sites were detected during execution, select a different Site row to display its details.

Implementing Modeling Assumptions Later When Adding Parallel Code

In the lower-right part of the Suitability Report under
Runtime Modeling
, changing a checkmark does not resolve an issue - it configures the modeling of your proposed parallel program execution. To implement the modeled improvements indicated by the check boxes, use specific parallel framework constructs in the
Add Parallel Framework
step of the workflow and consider .

Product and Performance Information

1

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