Intel® Trace Analyzer and Collector

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Introduction

Intel® Trace Collector is a tool for tracing MPI applications. It intercepts all MPI calls and generates tracefiles that can be analyzed with Intel® Trace Analyzer for understanding the application behavior. Intel® Trace Collector can also trace non-MPI applications, like socket communication in distributed applications or serial programs. The tool was formerly known as Vampirtrace* (VT), which is why the VT abbreviation is present in the names of some of components and variables.

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Collecting Lightweight Statistics

Intel® Trace Collector can gather and store statistics about the function calls and their communication. These statistics are gathered even if no trace data is collected, so it is a good starting point for trying to understand an unknown application that might produce an unmanageable trace.

Usage Instructions

To collect this light-weight statistics for your application, set the following environment variables before tracing:

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VT_countsetcallback

int VT_countsetcallback( VT_CountCallback_t callback, void *custom, int ncounters )

Description

Sets a callback for counter sampling for the calling thread.

The data provided by the callback is logged with the same time stamp as the event that triggered the callback. The callback must be set for each thread individually. Setting NULL disables sampling for the thread.

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SYNCED-HOST

Syntax

SYNCED-HOST [on|off]

Variable

VT_SYNCED_HOST

Default

off

Description

Use this setting to override whether Intel Trace Collector treats the clock of all processes one the same node as synchronized or not. Whether Intel Trace Collector makes that assumption depends on the selected time source.

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Buffer Given to MPI Cannot Be Read or Written

(LOCAL:MEMORY:INACCESSIBLE)

During the check for LOCAL:MEMORY:ILLEGAL_MODIFICATION of a send buffer Intel® Trace Collector will read each byte in the buffer once. This works for contiguous as well as non-contiguous data types. If any byte cannot be read because the memory is inaccessible, a LOCAL:MEMORY:INACCESSIBLE is reported. This is an error because it is only possible to proceed by skipping the entire operation.

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