Tutorial

Analyze MPI Applications with Intel® Trace Analyzer and Collector and Intel® VTune™ Profiler

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ID 773180
Date 3/31/2023
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Document Table of Contents
Document Table of Contents x
Analyze MPI Applications with Intel® Trace Analyzer and Collector and Intel® VTune™ Profiler
Analyze MPI Applications with Intel® Trace Analyzer and Collector and Intel® VTune™ Profiler x
Prerequisites Starting Intel® Trace Analyzer Starting Intel® VTune™ Profiler Analyzing an MPI Application Summary Notices and Disclaimers
Analyzing an MPI Application x
Optimizing MPI Communications Improving Intra-process Performance
Optimizing MPI Communications x
Prepare for Analysis Ungroup MPI Functions Detect Serialization in Function Profile and Message Profile Compare Original Trace File With Idealized Trace File Remove Serialization Compare Two Trace Files Analyze Optimized Communications
Improving Intra-process Performance x
Run Basic Hotspots Analysis Interpret Results
Analyze MPI Applications with Intel® Trace Analyzer and Collector and Intel® VTune™ Profiler

Ungroup MPI Functions

Analyze MPI process activity in your application.

To see the particular MPI functions called in the application, right-click on MPI (marked with a red rectangle) in the Event Timeline and select Ungroup Group MPI. This operation exposes the individual MPI calls.



After ungrouping the MPI functions, you see that the processes communicate with their direct neighbors using MPI_Sendrecv at the start of the iteration.



This data exchange has a disadvantage: process i does not exchange data with its neighbor i+1 until the exchange between i-1 and i is complete. This delay appears as a staircase pattern resulting with the processes waiting for each other.

The MPI_Allreduce at the end of the iteration resynchronizes all processes; that is why this block has the reverse staircase appearance.

Parent topic: Optimizing MPI Communications
Level Two Title