Intel® Advisor User Guide

User Guide

Contents

Collection Controls 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
.
Depending on an accuracy level and analyses you choose for a perspective, different overhead is added to your application execution time.
For example:
Runtime Overhead / Analysis
Survey
Characterization
Dependencies
MAP
Target application runtime with
Intel® Advisor
 compared to runtime without
Intel® Advisor
1.1x longer
2 - 55x longer
5 - 100x longer
5 - 20x longer

Solutions

Use the following techniques to skip
uninteresting
 parts of your target application, such as the initialization phase, and analyze only
interesting
 parts.

Pause Collection/Resume Collection Using Annotations

Minimize collection overhead.
Applicable analyses: Survey, Dependencies.
Some analysis types recognize the structural annotations typically used in the
Threading
 perspective
 workflow.
Use when:
  • Modifying/recompiling your target application is not an issue.
  • You do not want to analyze one or more uninteresting parts of your target application.
  • The interesting parts of your target application involve large workloads (because Pause/Resume API call frequency is about 1 Hz, and the operations pause and resume data collection in all processes in the analysis run, with the corresponding collection state notification to the GUI).
To pause collection, add the following annotation to your code:
  • C++:
    ANNOTATE_DISABLE_COLLECTION_PUSH
  • Fortran:
    call annotate_disable_collection_push()
  • C#:
    Annotate.DisableCollectionPush()
    ;
To resume collection, add the following annotation to your code:
  • C++:
    ANNOTATE_DISABLE_COLLECTION_POP
  • Fortran:
    call annotate_disable_collection_pop()
  • C#:
    Annotate.DisableCollectionPop();
C# and .NET support is deprecated starting
Intel® Advisor
 2021.1.

Pause Collection/Resume Collection Using API Methods

Minimize collection overhead using the Intel® Instrumentation and Tracing Technology (ITT) API.
For MPI applications, you can also use a standard MPI-specific function
MPI_Pcontrol(
<N>
)
 to pause and resume data collection. This function requires no changes in the application building process, unlike the ITT API calls, which require linking of a static ITT API library. See Analyze MPI Workloads.
Applicable analyses: Survey,
Characterization with Trip Counts or FLOP collection enabled
.
Use when:
  • Modifying/recompiling your target application is not an issue.
  • You do not want to analyze one or more uninteresting parts of your target application.
  • The interesting parts of your target application involve large workloads (because Pause/Resume API call frequency is about 1 Hz, and the operations pause and resume data collection in all processes in the analysis run, with the corresponding collection state notification to the GUI).
Prerequisites:
  • Add the following statements to every source file you want to instrument:
    • C/C++:
      ittnotify.h
    • Fortran:
      USE ITTNOTIFY
    • The
      ittnotify
       header file contains definitions of ITT API routines and important macros that provide the correct logic of API invocation from an application.
    • The ITT API is designed to incur almost zero overhead when tracing is disabled. If you need completely zero overhead, you can compile out all ITT API calls from an application by defining the
      INTEL_NO_ITTNOTIFY_API
       macro in your project at compile time, either on the compiler command line or in your source file prior to including the
      ittnotify
       header file.
  • Configure your build system to reach ITT API header file and libraries, where
    <install-dir>
     is the
    Intel Advisor
     installation directory.
    • Add the appropriate entry to your INCLUDE path:
      • C++:
        <install-dir>/sdk/include
      • Fortran:
        <install-dir>/sdk/include/lib32
         or
        <install-dir>/sdk/include/lib64
      • Microsoft Visual Studio* IDE:
        Project Properties
        C/C++ | Fortran
        General
        Additional Include Directories
        .
    • Add
      <install-dir>/sdk/lib32
       or
      <install-dir>/sdk/lib64
       to your LIBRARIES path.
      Visual Studio IDE:
      Project Properties
      C/C++ | Fortran
      General
      Additional Include Libraries
      .
    The ITT API headers, static libraries, and Fortran modules previously located at
    <install-dir>/include
     and
    <install-dir>/[lib32 | lib64]
     folders were moved to the
    <install-dir>/sdk/include
     and
    <install-dir>/sdk/[lib32 | lib64]
     folder. Copies of these files are retained at their old locations for backward compatibility and these copies should not be used for new projects.
  • Link your target application to the static library
    libittnotify.a
     (Linux* OS) or
    libittnotify.lib
     (Windows* OS) by passing
    -littnotify
     to your compiler. If tracing is enabled, this static library loads the ITT API implementation and forwards ITT API instrument data to the
    Intel Advisor
    . If tracing is disabled, the static library ignores ITT API calls, providing nearly zero instrumentation overhead.
    Visual Studio IDE:
    Project Properties
    Linker
    Input
    Additional Dependencies
  • Insert
    _itt_pause
     (C/C++) or
    CALL ITT_PAUSE
     (Fortran) before uninteresting parts of your target application and the
    _itt_resume
     (C/C++) or
    CALL ITT_RESUME
     (Fortran) before interesting parts of your target application.
    Example 1: The following snippet plus the standard run control collects analysis data twice - at the beginning and the middle of the snippet: 
    #include <ittnotify.h>
int main(int argc, char* argv[])
{
// Do work here
__itt_pause();
// Do uninteresting work here
__itt_resume();
// Do work here
__itt_pause();
// Do uninteresting work here
return 0;
}
    Example 2: The following snippet plus the standard run control collects analysis data only once - in the middle of the snippet: 
    #include <ittnotify.h>
int main(int argc, char* argv[])
{
__itt_pause();
// Do uninteresting work here
__itt_resume();
// Do work here
__itt_pause();
// Do uninteresting work here
return 0;
}
    Example 3: The following snippet plus the standard run control collects analysis data only once - at the end of the snippet: 
    #include <ittnotify.h>
int main(int argc, char* argv[])
{
__itt_pause();
// Do uninteresting work here
__itt_resume();
// Do work here
return 0;
}
    Example 4: The following snippet plus the
    Start Paused
     control collects analysis data only once - at the end of the snippet: 
    #include <ittnotify.h>
int main(int argc, char* argv[])
{
// Do uninteresting work here
__itt_resume();
// Do work here
return 0;
}
After
 performing the prerequisites and recompiling, do one of the following:
Info
: In the commands below, make sure to replace the
myApplication
 with your application executable path and name
before
 executing a command. If your application requires additional command line options, add them
after
 the executable name.
  • Click the standard run control or the
    Start Paused
     control on the
    Analysis Workflow
     pane to run the desired analysis.
  • Use the
    advisor
     CLI action
    --collect
     with or without the CLI action option to run the desired analysis. For example: 
    advisor --collect=survey --project-dir=./advi_results -- ./myApplication
To attach ITT APIs to a launched application, that is, to collect API data on an application that is already launched, point the target application to the
ittnotify_collector
library using an environment variable:
  • Windows* OS:
    set INTEL_LIBITTNOTIFY32=<install_dir>\bin32\runtime\ittnotify_collector.dll
    set INTEL_LIBITTNOTIFY64=<install_dir>\bin64\runtime\ittnotify_collector.dll
  • Linux* OS:
    export INTEL_LIBITTNOTIFY32=<install_dir>/lib32/runtime/libittnotify_collector.so
    export INTEL_LIBITTNOTIFY64=<install_dir>/lib64/runtime/libittnotify_collector.so
Use the full path to the library without quotations marks.
After you complete configuration, start the instrumented application in the correct environment.
Intel® Advisor
 collects API data even if the application is launched before the
Intel® Advisor
 is launched.
You can find the
ITT API documentation
 at https://github.com/intel/ittapi.

Start Target Application With Collection Paused

Minimize collection overhead.
Applicable analyses: Survey,
Characterization with Trip Counts and FLOP collection enabled
.
Use when you do not want to analyze the early phase(s) of your target application, such as the initialization phase, but you want analysis in
ready mode
.
Info
: In the commands below, make sure to replace the
myApplication
 with your application executable path and name
before
 executing a command. If your application requires additional command line options, add them
after
 the executable name.
To implement, do one of the following:
  • Click the associated control on the
    Analysis Workflow
     pane to run the desired analysis.
  • Use the
    advisor
     CLI action option when you run the desired analysis. For example: 
    advisor --collect=survey --start-paused --project-dir=./advi_results -- ./myApplication
You can use different techniques to resume collection. The most common is
__itt_resume
.

Start Target Application With Collection Paused/Resume Collection After N Seconds

Minimize collection overhead.
Applicable analyses: Survey,
Characterization with Trip Counts and FLOP collection enabled
.
Use when...
  • You do not want to modify/recompile your target application.
  • You do not want to analyze the initialization phase of your target application.
  • You have a good idea of the time interval of interest, but pinpointing the exact beginning of the interesting part of your target application is not important.
  • The interesting part of your target application is more than a few loops.
Info
: In the commands below, make sure to replace the
myApplication
 with your application executable path and name
before
 executing a command. If your application requires additional command line options, add them
after
 the executable name.
To implement, do one of the following:
  • Enable the
    Project Properties
    Analysis Target
    [Name] Analysis
    Advanced
    Automatically resume collection after (sec)
     checkbox and supply the desired value
    , where
    [Name]
     is Survey or Trip Counts and FLOP
    .
    Click the standard run control on the
    Analysis Workflow
     pane to run the desired analysis. (Collection automatically starts in the paused state.)
  • Use the
    advisor
     CLI action option
    --resume-after=<integer>
     when your run the desired analysis. For example: 
    advisor --collect=survey --resume-after=30 --project-dir=./advi_results -- ./myApplication
Use a value representing seconds in the GUI field and milliseconds in the integer argument.

Stop Collection After N Seconds

Minimize collection overhead.
Applicable analyses: Survey,
Characterization with Trip Counts and FLOP collection enabled
, Dependencies, Memory Access Patterns.
This is the flip side of the
Start target application with collection paused
 technique. Use when...
  • You do not want to modify/recompile your target application.
  • You do not want to analyze the end of your target application.
  • You have a good idea of the time interval of interest, but pinpointing the exact end of the interesting part of your target application is not important.
  • The interesting part of your target application is more than a few loops.
To implement, enable
Project Properties
Analysis Target
[Name] Analysis
Advanced
Automatically stop collection after (sec)
 checkbox and supply the desired value
, where
[Name]
 is Survey or Trip Counts and FLOP
.
Click the standard run control on the
Analysis Workflow
 pane to run the desired analysis.
Use a value representing seconds in both the GUI field and integer argument.

Stop Collection

Minimize collection overhead.
Applicable analyses: Survey,
Characterization with Trip Counts and FLOP collection enabled
, Dependencies, Memory Access Patterns.
Use when...
  • You do not want to modify/recompile your target application.
  • You do not want to analyze the end of your target application.
  • You can detect the time interval of interest based on target application output.
  • The interesting part of your target application is more than a few loops.
To implement, do one of the following:
  • Click the associated control on the
    Analysis Workflow
     pane when running the desired analysis.
    If running a Dependencies or Memory Access Patterns analysis, use the
    Site Coverage
     bar to determine when all marked loops are analyzed at least once:
    Intel Advisor: Site coverage bar
  • Use the
    advisor
     CLI action
    --command=stop
     when you run the desired analysis. For example: 
    advisor --command=stop --result-dir=./myAdvisorResult

Manually Pause Collection/Manually Resume Collection

Minimize collection overhead.
Applicable analyses: Survey,
Characterization with Trip Counts and FLOP collection enabled
.
Use when...
  • You can detect the time interval of interest based on target application output.
  • Your need to pause or resume is unplanned and spontaneous.
To implement, do one of the following to pause analysis data collection (the target application continues running, but analysis data collection stops):
  • Click the associated control on the
    Analysis Workflow
     pane when running the desired analysis.
  • Use the
    advisor
     CLI action
    --command=pause
     when you run the desired analysis. For example: 
    advisor --command=pause --result-dir=./myAdvisorResult
Do one of the following to resume analysis data collection:
  • Click the associated control on the
    Analysis Workflow
     pane.
  • Use the
    advisor
     CLI action
    --command=resume
    . For example: 
    advisor --command=resume --result-dir=./myAdvisorResult

Attach to Process/Detach from Process

Minimize collection overhead.
Applicable analyses: Survey,
Characterization with Trip Counts and FLOP collection enabled
 without call stacks.
This technique is similar to the
Start target application with collection paused
 technique, except you can attach to an already running process. This is particularly beneficial if:
  • The process is a service that runs forever.
  • The launching infrastructure is relatively complicated, such as a sequence of scripts that must be modified to embed a
    launch collection
     command.
GUI:
  1. Choose
    Project Properties
    Analysis Target
    [Name] Analysis
    > Launch Application
     drop-down list
    > Attach to Process
    , where
    [Name]
     is Survey or Trip Counts and FLOP
    .
  2. Disable the
    Inherit settings from Survey Hotspots Analysis Type
     checkbox.
  3. Choose the
    Process name
     or
    PID
     option and identify a process.
  4. Supply other information as desired and close the
    Project Properties
     dialog box.
  5. Click the standard run control on the
    Analysis Workflow
     pane to run the desired analysis.
CLI: Use the
advisor
 CLI action option
--target-pid=<unsigned integer>
 or
--target-process=<string>
 to attach to a process when running the desired analysis. For example: 
advisor --collect=survey --project-dir=./advi_results --result-dir=./myAdvisorResult --target-process=myProcess
Do one of the following to stop collecting analysis data on a process (the process continues running but analysis data collection stops):
  • Click the associated control on the
    Analysis Workflow
     pane.
  • Use the
    advisor
     CLI action
    --command=detach
    . For example: 
    advisor --command=detach --result-dir=./myAdvisorResult
  • Ensure call stacks are disabled (which is the default setting) if you run the
    Characterization with Trip Counts and FLOP collection enabled
     analysis:
    • Disable the
      Project Properties
      Analysis Target
      Trip Counts and FLOP Analysis
      Advanced
      Collect stacks
      checkbox.
    • Add the
      advisor
       CLI action option to the
      --collect
       command, or simply omit a action option on the
      --collect
       command.
  • Using the
    advisor
     CLI action
    --command=stop
     kills the process (which also stops analysis data collection).

Product and Performance Information

1

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