Use the comsol command to start COMSOL products with detailed start-up options.

where square brackets indicate optional arguments. The comsol command can be combined with optional targets to achieve various results. The table below lists the command and targets:

The comsol command is located in the bin folder in the COMSOL installation directory.

There is a number of .ini files in the subdirectories glnx86 and glnxa64 in the bin directory. It is sometimes recommended that you edit these files. For example, you can add options to any of the above commands by modifying the corresponding ini file. To change the option opt to value val, add the line

to the file comsol.ini. Change the file comsolbatch.ini for comsol batch, and similarly for the other COMSOL targets.

You can enter various options after the comsol command and target. Table 22-16 lists the options (See [<options>] in the command syntax) available for all comsol commands. Always issue these options between the command and the target (if any).

For the -tmpdir option, the COMSOL Multiphysics software uses the specified directory to store temporary files. Use the -prefsdir option to specify the directory where COMSOL Multiphysics stores the preference file.

In a default COMSOL Multiphysics installation, the documentation files are located in the directory doc under the installation root directory. You can use the -docroot option if you want to move the documentation directory to a different location. Similarly, use the -applicationsroot option if you want to move the Application Libraries root directory applications from its default location under the COMSOL Multiphysics installation root. Relocating the documentation and Application Libraries root directories can be useful for administering Application Library Update; see The Application Library Update Window.

Use the option -np to control the number of cores used. The default is to use all available cores (processing units).

Use the option -numasets to control the number of nonuniform memory access (NUMA) node sets that the COMSOL Multiphysics software should take into account. This is usually the number of processor sockets that the hardware is using. If you only set the -np option, the number of sockets is determined automatically so that sufficient number of sockets are used by default.

Depending on how loaded the machine is, you can control how COMSOL Multiphysics uses the available processors with the -mpmode option. The following options are available:

Use the option -alloc to specify memory allocator type. The default is to use the native memory allocator. The scalable memory allocator can increase performance significantly for computers with many cores but uses more memory.

If you want to use a different BLAS library than the ones provided by COMSOL, make sure that COMSOL Multiphysics can find the library. The simplest way for COMSOL Multiphysics to find a library is to put it in /lib/win64 or somewhere in the standard search path. Also provide the path to any sublibraries needed by the library. Set the search path to point to the directory where the library is installed. To do so, use the environment variable PATH. Your library must support both the standard FORTRAN LAPACK interface and the standard FORTRAN BLAS interface. If your LAPACK and BLAS interface consists of several libraries, use the path to the LAPACK library.

By default COMSOL Multiphysics uses the GCC libraries installed on the system. If COMSOL Multiphysics is unable to start, the software uses the GCC libraries shipped with COMSOL Multiphysics. The option -forcegcc is intended for use together with the LiveLink™ for MATLAB®; use it if you are unable to make function callbacks to MATLAB.

The following options are used to specify inputs to an application with command-line options.Find more information about these options in the section The Application Argument Node in the Application Builder Reference Manual.

In additions to the options in Table 22-16, the standalone COMSOL command supports the following options on Linux.

Use a COMSOL Multiphysics server command to start a COMSOL process ready to process computational requests. A COMSOL Multiphysics server listens for TCP/IP connections from COMSOL Multiphysics clients. A COMSOL Desktop can become a COMSOL Multiphysics client by connecting to a COMSOL Multiphysics server. The LiveLink™ for MATLAB® also needs to connect to a COMSOL Multiphysics server.

To access the computer running the COMSOL Multiphysics server, simply log in on the server computer by using ssh or a similar command, then enter the comsol mphserver command.

When you start a COMSOL Multiphysics server for the first time, you are asked for a username and password. Select a username and a password, which COMSOL then uses in communications between the COMSOL Multiphysics client and the server. You must also specify a matching username and password in the Connect to Server dialog box. The software writes this login information in the subdirectory .comsol/v54/login.properties in your home directory.

To enhance security, you can limit the address range that can access the COMSOL Multiphysics server, both in your firewall and by changing the COMSOL Multiphysics server configuration. To limit the allowed address range in the server, edit the file <COMSOL Installation Directory>/bin/conf/server.xml and find the lines:

The default port for the COMSOL Multiphysics server is 2036. You can change this by using the option -port <port> when launching COMSOL and COMSOL Multiphysics server.

To serve the COMSOL Desktop with documentation, COMSOL Multiphysics opens a separate documentation server on the client computer when you open the documentation. The documentation server program, comsoldocserver.exe, is always installed, even when you choose online documentation. It is nontrivial to start the documentation server, so it is typically only started from comsol.exe or comsoldoc.exe.

To enhance security, you can limit the address range that can access the documentation server, both in your firewall and by changing the documentation server configuration. To limit the allowed address range in the server, edit the file <COMSOL Installation Directory>/doc/help/conf/server.xml and find the lines:

and follow the instructions. The default port for the documentation server when started from comsol.exe is 8090 or the nearest higher free port. You can change this by using the option -docport <docport> when launching COMSOL. The port used by the documentation server when started from comsoldoc.exe is 8390 or the nearest higher free port.

where <level> is the level to stop the process on. Set the level to a high value in order to stop as soon as possible. By default, it is set to 100. The -inputfile option indicates the filename of the model that another process is running. The inputfile arguments should be consistent with the one specified to launch another process. That is, either the same inputfile arguments should be provided or the -inputfile should be the same as the -outputfile specified to launch another process.

This command starts COMSOL Multiphysics in batch mode, solves the model in the Model MPH-file with the given filename using the active solver settings in the model, and stores the solution in the out.mph.

The -study option directs COMSOL Multiphysics to run a certain study. The study is identified by its tag. In the COMSOL Desktop, select Show Name and Tag under Model Builder Node Label to see the tags of the jobs under Study within curly braces in the Model Builder. In the model object, determine the tags of the jobs by the command model.study().tags(). You can determine the name of each study by model.study(<tag>).name() using one of the job tags.

The -job option works similarly to the -study option. It directs COMSOL Multiphysics to start a certain job. The job is identified by its tag. In the model object, determine the tags of the jobs by the command model.batch().tags(). You can determine the name of each job by model.batch(<tag>).name() using one of the job tags..

The -usebatchlic option makes COMSOL use batch licenses for the job. This option is equivalent to the Use batch license check box available in the Cluster Computing and Cluster Sweep study nodes. Using batch licenses for a cluster computing or cluster sweep job means that you can continue working in the COMSOL Desktop while the job is running using only a single FNL license.

The comsol compile command compiles a model file for Java for use by the COMSOL batch command or for loading class files into the GUI. With COMSOL Compiler, you can also use it to compile COMSOL apps into standalone executable apps. The Linux syntax for the COMSOL compile command is

Options not given are taken from the application’s Compiler node, except for -outputdir and -platforms.

Use the comsol command with the option -nn <no. of nodes>. -nn specifies the total number of compute nodes created. A COMSOL instance resides in each compute node and communicates with other compute nodes using MPI. A compute node is a process running on the operating system, and multiple compute nodes can be assigned to run on a single host.

The preferred way of starting COMSOL cluster jobs is from the Study node in the COMSOL Desktop. If you need to start COMSOL cluster jobs from the command line, the preferred way is to use the comsol -nn <nn> batch command because the comsol -nn <nn> mphserver and comsol -nn <nn> commands require TCP/IP access from your client computer to the cluster node where COMSOL runs.

The file <filename> should contain the hostnames of the physical nodes (or, alternatively, host) that you intend to use. You can find out the hostname of each physical node from the hostname command. Each physical node should be listed on a separate line in the file. You can also list the IP address of each physical node. The file can contain more hosts than you intend to use.

Previously there was a shorthand for performing the COMSOL MPI environment initialization and starting COMSOL Multiphysics. The -clustersimple option is still supported but performs the same Hydra MPI initialization as other COMSOL command with cluster options specified. For example,

So when no COMSOL cluster options are included in the command, the use of -clustersimple instructs the Intel MPI library to automatically detect the number of nodes that were scheduled to the program. However, explicitly setting the number of processes with the -nn option is common practice, as COMSOL Multiphysics can combine MPI with multithreading to obtain more efficient performance. If the -nn option is specified, then the -clustersimple option has no additional effect.

The following three examples show the command for starting distributed computing with COMSOL Desktop, COMSOL Multiphysics Server, and COMSOL batch mode, respectively. Each starts 4 computational nodes, one on each of the 4 hosts listed in the file hostfile:

It is possible to specify the number of CPU cores for each COMSOL process. The following command uses the option -np 2 to assign 2 CPU cores to each compute node:

For additional command-line options, see COMSOL Cluster Options in Table 22-28.

There are several implementations of MPI. COMSOL Multiphysics is shipped with the Intel MPI library but also supports most MPI implementations based on MPICH2. It is recommended that you use the default Intel MPI library. For running COMSOL Multiphysics on a computer that has MPICH2 installed, the COMSOL software also has a compatibility mode that you can activate by adding the option -mpi mpich2. When using this option, both the variables PATH and LD_LIBRARY_PATH must include your MPI implementation. It is also possible to use other MPI libraries based on MPICH2 using the option -mpipath <path to shared library> and -mpiroot <path to root of mpi library installation>. Table 22-16 lists the MPI related options, -mpi, -mpipath, -scalapack, and -scalapackpath. Additionally, the COMSOL MPI arguments are configurable inside the COMSOL start script. To configure COMSOL to work with a job scheduler through the Cluster Computing study, you can set the options

in the comsol.ini file. This adds commands prior to the comsol command and after the comsol command. You can add {nn} or {perhost} to any of these pre- or postcommands. This configures the Cluster Computing study to use the number of nodes and number of nodes on each host from the corresponding settings for the Cluster Computing study. For more information, see Cluster Computing.

Use the -h switch for more information about each command, typing, for example, comsol -h hydra cleanup.

COMSOL Multiphysics ships with the Intel MPI library but should be compatible with most MPICH2 compatible MPI libraries. To download the latest version of Intel MPI library runtime visit http://software.intel.com/en-us/intel-mpi-library. To run COMSOL Multiphysics with another version of Intel MPI or other MPI library, set -mpiroot to the root path of the MPI library. In case the downloaded library is not compatible with the version COMSOL Multiphysics uses (this should usually not be the case), also set -mpipath to the dynamically loaded library that should be used. The default of the Intel MPI library is to use ssh as communication protocol. If you require another communication protocol, use the option -mpibootstrap <protocol>. If you are using a scheduler, the Intel MPI library can often detect the environments it is running in automatically, in which case you may not need to provide additional cluster options in the COMSOL command.

In some cases it helps if you combine the option with the environment variable PSM_SHAREDCONTEXTS_MAX set to 1. You can control the fabrics used for communication with the option -mpifabrics fabric1:fabric2, where fabric1 is equal to fabric2 or fabric1 is shm.

If COMSOL Multiphysics aborts during start, make sure that all nodes can access the license manager and that COMSOL Multiphysics can be started on each node when not running distributed. Sometimes there is additional information in the log files located in $HOME/.comsol/v54/configuration/comsol/*.log. If this does not help, start the MPI test program to make sure that the MPI library is working as it should using the following command:

For more verbose information about the startup process when using Hydra, use -mpiarg -verbose, or set -mpidebug to a value greater than the default 4.

Use the COMSOL matlab command to access the COMSOL API through MATLAB®. Enter:

The following options are available for the comsol mphserver matlab command: