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# 3.5.4 PARALLEL EXECUTION IN Abaqus/CFD

Products: Abaqus/CFD Abaqus/CAE

# References

• “Obtaining information,” Section 3.2.1   
• “Using the Abaqus environment settings,” Section 3.3.1   
• “Controlling job parallel execution,” Section 19.8.8 of the Abaqus/CAE User’s Guide, in the HTML version of this guide

# Overview

Parallel execution in Abaqus/CFD:

• reduces run time for analyses that require a large number of increments;   
• reduces run time for analyses that contain a large number of nodes and elements;   
• produces analysis results that are independent of the number of processors used for the analysis; and   
• is available for both shared memory computers and computer clusters using an MPI-based domain decomposition parallel implementation.

# Invoking parallel processing

Abaqus/CFD uses domain-based parallelism implemented with explicit message passing for both shared memory and distributed memory computers. All procedures provided by Abaqus/CFD and their associated features are fully parallel (“Parallel execution: overview,” Section 3.5.1). Parallel execution is invoked by specifying the number of processors to be used.

Input File Usage: Enter the following input on the command line:

abaqus job=job-name cpus=n

For example, the following input will run the job “manifold” on two processors:

abaqus job=manifold cpus=2

Abaqus/CAE Usage: Job module: job editor: Parallelization: toggle on Use multiple

processors, and specify the number of processors, n

# Domain-based parallelism

Abaqus/CFD uses a domain-decomposition message passing paradigm for its parallel implementation. An element-based decomposition strategy is used that minimizes the number of communications required between subdomains while providing a nearly uniform computational work distribution among the processors. The number of domains maps exactly to the number of user-specified processors for a given calculation. The load-balancing procedures are implemented in parallel as well, so that

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you can avoid time consuming serial load-balancing procedures at the start of a calculation. Every attempt has been made to ensure that Abaqus/CFD provides scalable parallel solutions for a broad range of applications. All procedures and features in Abaqus/CFD are provided with a fully parallel implementation. All output is serialized automatically for the user so that there is no translation between parallel domains and the original user input. In addition, this permits Abaqus/CFD to restart seamlessly on any number of processors, regardless of how many were used for the original computation.

# Co-simulation

The co-simulation technique (“Co-simulation: overview,” Section 17.1.1) for run-time coupling of Abaqus/CFD to Abaqus/Standard or to Abaqus/Explicit can be used with Abaqus/CFD running either in serial or parallel.

# Restart

There are no restrictions on features that can be included in steps defined in a restart analysis. The number of processors used for the restart analysis is not required to be the same as the number of processors used in the original analysis.

# Output

There are no output restrictions.

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# 3.6 File extension definitions

• “File extensions used by Abaqus,” Section 3.6.1

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# 3.6.1 FILE EXTENSIONS USED BY Abaqus

Products: Abaqus/Standard Abaqus/Explicit Abaqus/CFD

# Reference

• “Execution procedure for Abaqus: overview,” Section 3.1.1

# Overview

The abaqus procedure generates several files. Some of these files contain analysis, postprocessing, and translation results and are retained for use by other analysis options, restarting, or postprocessing. This section describes the files that are created and retained by Abaqus.

Other files exist only while Abaqus is executing and are deleted when a run completes. These temporary files are generated in the scratch directory. The number and types of temporary files generated depend on the analysis procedures, memory management parameters, and environment settings.

Certain file extensions used by Abaqus are also used by other software applications. You must handle any file extension conflicts with other applications.

# File extensions

abq

State file, only used by Abaqus/Explicit. It is written by the analysis, continue, and recover options. It is read by the convert and recover options. This file is required for restart.

axi

Symmetric model data file, only used by Abaqus/Standard. It is written during symmetric model generation by the datacheck and analysis options.

bsp

Text file containing beam cross-section properties for meshed section profiles. It is written by Abaqus/Standard during meshed beam cross-section generation.

c

User subroutine or other special-purpose C file.

c++

User subroutine or other special-purpose C++ file.

cpp

User subroutine or other special-purpose C++ file.

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cid

Auto-release file, which contains information needed for license recovery and suspension.

com

Command file, created by the Abaqus execution procedure.

dat

Printed output file. It is written by the analysis, datacheck, parametercheck, and continue options. Abaqus/Explicit and Abaqus/CFD do not write analysis results to this file.

f

User subroutine or other special-purpose Fortran file.

fil

Results file. It is written by the analysis and continue options in Abaqus/Standard and by the convert=select and convert=all options in Abaqus/Explicit.

fin

Results file created when changing the format of the .fil file using the abaqus ascfil command. It can be in either ASCII or binary format. (See “ASCII translation of results (.fil) files,” Section 3.2.14.) The ASCII format is convenient for data transfer between machines that do not have compatible binary data formats.

inp

Analysis input file. It is read when the analysis, datacheck, and parametercheck options are selected.

ipm

Interprocess message file. It is written when an analysis is run from Abaqus/CAE, and it contains a log of all messages sent from Abaqus/Standard, Abaqus/Explicit, or Abaqus/CFD to Abaqus/CAE.

lck

Lock file for the output database. This file is written whenever an output database file is opened with write access; it prevents you from having simultaneous write permission to the output database from multiple sources. It is deleted automatically when the output database file is closed or when the analysis that creates it ends. The ask\_delete environment file parameter setting will not affect the lock file.

log

Log file, which contains start and end times for modules run by the current Abaqus execution procedure.

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# mdl

Model file, used by Abaqus/Standard and Abaqus/Explicit. It is written by the datacheck option. It is read and can be written by the analysis and continue options in Abaqus/Standard. It is read by the analysis and continue options in Abaqus/Explicit. Multiple model files may exist if the element operations are executed in parallel in an Abaqus/Standard analysis. In such a case a process identifier is attached to the file name. This file is required for restart.

# msg

Message file. It is written by the analysis, datacheck, and continue options in Abaqus/Standard and Abaqus/Explicit. Multiple message files may exist if the element operations are executed in parallel in an Abaqus/Standard analysis. In such a case a process identifier is attached to the file name.

# nck

Nickname file used by Abaqus/Standard. It stores a set of internal identifiers for the degrees of freedom in a model.

# odb

Output database. It is written by the analysis and continue options in Abaqus/Standard, Abaqus/Explicit, and Abaqus/CFD. It is read by the Visualization module in Abaqus/CAE (Abaqus/Viewer) and by the convert=odb option. This file is required for restart.

# pac

Package file, which contains model information and is used by Abaqus/Explicit only. It is written by the analysis and datacheck options. It is read by the analysis, continue, and recover options. This file is required for restart.

# par

Modified version of original parametrized input file showing input parameters and their values.

# pes

Modified version of original parametrized input file showing input free of parameter information (after input parameter evaluation and substitution has been performed).

# pmg

Parameter evaluation and substitution message file. It is written when the input file is parametrized.

# prt

Part file, used by Abaqus/Standard and Abaqus/Explicit. This file is used to store part and assembly information and is created even if the input file does not contain an assembly definition. The part file is required for restart, import, sequentially coupled thermal-stress analysis, symmetric model generation, and underwater shock analysis, even if the model is not defined in terms of an assembly of part instances. This file may also be needed for submodeling analysis.

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psf

Python scripting file. You must create this type of file to define a parametric study.

res

Restart file, which contains information necessary to continue a previous analysis and is used by Abaqus/Standard and Abaqus/Explicit. The restart file is written by the analysis, datacheck, and continue options. It is read by any restarted analysis.

sel

Selected results file, used by Abaqus/Explicit. It is written by the analysis, continue, and recover options and is read by the convert=select option. This file is required for restart.

sim

Model and results file, used by Abaqus/CFD. It is also used by Abaqus/Standard and Abaqus/Explicit when the resultsformat=sim or both option is specified. It is written by the datacheck option. It is read and can be written by the analysis and continue options. This file is required for restart.

Linear dynamics data file, used by Abaqus/Standard when the resultsformat=odb option is specified. It is written during the frequency extraction procedure in SIM-based linear dynamics analyses (see “Using the SIM architecture for modal superposition dynamic analyses” in “Dynamic analysis procedures: overview,” Section 6.3.1, for details) and is used to store eigenvectors, substructure matrices, and other modal system information. This file is required for restart.

sta

Status file. Abaqus writes increment summaries to this file in the analysis, continue, and recover options.

stt

State file. It is written by the datacheck option in Abaqus/Standard and Abaqus/Explicit. It is read and can be written by the analysis and continue options in Abaqus/Standard. It is read by the analysis and continue options in Abaqus/Explicit. Multiple state files may exist if the element operations are executed in parallel in an Abaqus/Standard analysis. In such a case a process identifier is attached to the file name. This file is required for restart.

sup

Substructure file, used by Abaqus/Standard.

var

File containing information about the input file variations generated by a parametric study.

023

Communications file, used by Abaqus/Standard and Abaqus/Explicit. It is written by the analysis and datacheck options and is read by the analysis and continue options.

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# 3.7 Fortran unit numbers

• “Fortran unit numbers used by Abaqus,” Section 3.7.1

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