User Guide

Contents

Miscellaneous Techniques to Minimize Analysis Overhead

Issue

Running your target application with the
Intel Advisor
can take substantially longer than running your target application without the
Intel Advisor
. For example:
Runtime Overhead / Analysis
Survey
Trip Counts & FLOP
Roofline
Dependencies
MAP
Target application runtime with
Intel Advisor
compared to runtime without
Intel Advisor
1.1x longer
3 - 8x longer
3.1 - 8.1x longer
5 - 100x longer
5 - 20x longer

Solutions

The following techniques may help minimize overhead without limiting collection scope.

Disable Cache Simulation

Minimize collection overhead.
Applicable analyses:
  • Memory Access Patterns (base simulation functionality)
  • Trip Counts and FLOP
    (enhanced simulation functionality)
Implement these techniques when cache modeling information is not important to you:
The default setting for all the properties/options in the table below is disabled.
Path: Project Properties
Analysis Target
...
CLI Action Options
Description
Disable the
Memory Access Patterns Analysis
Advanced
Enable Memory-Level Roofline with cache simulation
checkbox.
--no-enable-cache-simulation
Do not model cache misses, cache misses and cache line utilization, or cache misses and loop footprint.
Disable the
Trip Counts and FLOP Analysis
Advanced
Enable CPU cache simulation
checkbox.
--no-enable-cache-simulation
Do not:
  • Model multiple levels of cache for data, such as counts of loaded of stored bytes for each loop.
  • Create simulations for specific cache hierarchy configurations.

Limit Reported Data

Applicable analysis: Memory Access Patterns.
Implement these techniques when the additional data is not important to you.
The default setting for all the properties/options in the table below is enabled.
Project Properties
Analysis Target
Memory Access Patterns Analysis
Advanced
CLI Action Options
Description
Disable the
Report stack variables
checkbox.
--no-record-stack-frame
Do not report stack variables for which memory access strides are detected.
Disable the
Report heap allocated variables
checkbox.
--no-record-mem-allocations
Do not report heap-allocated variables for which memory access strides are detected.

Minimize Data Set

Minimize collection overhead.
Applicable analyses: All, but especially Dependencies, Memory Access Patterns.
When you run an analysis, the
Intel Advisor
executes the target against the supplied data set. Data set size and workload have a direct impact on target application execution time and analysis speed
For example, it takes longer to process a 1000x1000 pixel image than a 100x100 pixel image. A possible reason: You may have loops with an iteration space of 1...1000 for the larger image, but only 1...100 for the smaller image. The exact same code paths may be executed in both cases. The difference is the number of times these code paths are repeated.
You can control analysis cost without sacrificing completeness by minimizing this kind of unnecessary repetition from target application execution.
Instead of choosing large, repetitive data sets, choose small, representative data sets that minimize the number of instructions executed within a loop while thoroughly exercising target application control flow paths.
Your objective: In as short a runtime period as possible, execute as many paths as you can afford, while minimizing the repetitive computation within each task to the bare minimum needed for good code coverage.
Data sets that run in about ten seconds or less are ideal. You can always create additional data sets to ensure all your code is checked.

Temporarily Disable Finalization

Minimize finalization overhead.
Applicable analyses:
Roofline,
Survey,
Trip Counts and FLOP
.
Use when you plan to view collected analysis data on a different machine. Finalization automatically occurs when a result is opened in the GUI or a report is generated from the result.
To implement, do one of the following while running an analysis:
  • When the analysis
    Finalizing data...
    phase begins, click the associated
    Cancel
    button.
    Intel Advisor control: Finalize Cancel button
  • Use the
    advixe-cl
    CLI action option
    --no-auto-finalize
    when you run the desired analysis. For example:
    advixe-cl --collect=survey --project-dir=./myAdvisorProj --no-auto-finalize -- ./bin/myTargetApplication

Product and Performance Information

1

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