Quick performance evaluation with VTune APS or detailed hotspot, memory, or threading analysis with VTune profiler.

First load the environment module:

module add vtune/XXXX

Intro:
https://ci.spdk.io/download/2019-summit-prc/02_Presentation_02_VTune_and_Analyzers_Overview_Sri.pdf
www.intel.com/content/www/us/en/docs/vtune-profiler/get-started-guide/2023/linux-os.html

Manuals:
Intel_APS.pdf
VTune_features_for_HPC.pdf

vtune -help

Run VTune via the command line interface

Run your application with VTune wrapper as follows:
www.intel.com/content/www/us/en/docs/vtune-profiler/user-guide/2023-0/command-line-interface.html

Minimal Application Performance Snapshot (APS)

mpirun -np 4 aps -collect hotspots advanced-hotspots ./path-to_your/app.exe args_of_your_app

# after completion, explore the results:
aps-report aps_result_*

Full Hotspot Analysis

mpirun -np 4 vtune –collect hotspots -result-dir vtune_hotspot ./path-to_your/app.exe args_of_your_app

# after completion, explore the results:
vtune -report summary -r vtune_*

Run VTune-GUI (not recommended)

Login with x-window support (ssh -X) and then start

vtune-gui

Run VTune-GUI remotely on your local browser (recommended)

Login to the supercomputer with local port forwarding and start your VTune server on an exclusive compute node (1h job):

ssh -L 127.0.0.1:55055:127.0.0.1:55055 blogin.hlrn.de
salloc -p standard96:test -t 01:00:00
ssh -L 127.0.0.1:55055:127.0.0.1:55055 $SLURM_NODELIST
module add intel/19.0.5 impi/2019.9 vtune/2022
vtune-backend --web-port=55055 --enable-server-profiling &

Open 127.0.0.1:55055 in your browser (allow security exception, set initial password).

In 1^st "Welcome" VTune tab (run MPI parallel Performance Snapshot):

Click: Configure Analysis
-> Set application: /path-to-your-application/program.exe
-> Check: Use app. dir. as work dir.
-> In case of MPI parallelism, expand "Advanced": keep defaults but paste the following wrapper script and check "Trace MPI":

#!/bin/bash

# Run VTune collector (here with 4 MPI ranks)
mpirun -np 4 "$@"

Under HOW, run: Performance Snapshot.
(After completion/result finalization a 2^nd result tab opens automatically.)

In 2^nd "r0..." VTune tab (explore Performance Snapshot results):

-> Here you find several analysis results e.g. the HPC Perf. Characterization.
-> Under Performance Snapshot - depending on the snapshot outcome - VTune suggests (see % in the figure below) more detailed follow-up analysis types:

--> For example select/run a Hotspot analysis:

In 3^nd "r0..." VTune tab (Hotspot analysis):

-> Expand sub-tab Top-down Tree
--> In Function Stack expand the "_start" function and expand further down to the "main" function (first with an entry in the source file column)
--> In the source file column double-click on "filename.c" of the "main" function

-> In the new sub-tab "filename.c" scroll down to the line with maximal CPU Time: Total to find hotspots in the main function

To quit the debug session press "Exit" in the VTune "Menu" (upper left symbol of "three horizontal bars"). Then close the browser page. Exit your compute node via CTRL+D and kill your interactive job:

squeue -l -u $USER
scancel your-job-id

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