Link 0 Commands Summary

This section lists all Link 0 commands, which are optional and precede the route section. Detailed discussions of their use are found elsewhere.

Link 0 commands may be up to 500 characters in length.

Sets the amount of dynamic memory used to N 8-byte words (default). This value may also be followed by KB, MB, GB, TB, KW, MW, GW or TW (without intervening spaces) to specify units of kilo-, mega-, giga- or tera-bytes or words. The default memory size is 256 MB.

Locates and names the checkpoint file.

The contents of the checkpoint file specified by %OldChk are copied to the checkpoint file of the current job step at the start of the job step. This allows data to be picked up from a previous calculation without destroying anything on the checkpoint file from it.

Locates and names a single, unified read-write file (old-style syntax).

%RWF=loc1,size1,loc2,size2, …
An alternate syntax is provided for splitting the read-write file among two or more disks (or file systems). Each location is followed by a maximum size for the file segment at that location. The size of each file segment is given in 8-byte words (default). This value may also be followed by KB, MB, GB, TB, KW, MW, GW or TW (without intervening spaces) to specify units of kilo-, mega-, giga- or tera-bytes or words. A value of -1 for any size parameter indicates that any and all available space may be used, and a value of 0 indicates that an existing segment should retain its current size. The locations may be either directory locations, or full pathnames. Note that directory specifications must include terminal slashes (on UNIX systems).

Locates and names the two-electron integral file(s). spec may take on either of the forms used for the read-write file.

Locates and names the two-electron integral derivative file(s). spec may take on either of the forms used for the read-write file.

%KJob LN [M]
Tells the program to stop the run after the Mth occurrence of Link N. For example, %KJob L502 2 will cause the run to terminate after Link 502 has been run for the second time. M may be omitted; it defaults to 1.

Causes Link 0 to save scratch files at the end of the run. By default, all non-specified scratch files are deleted and all named scratch files are saved when the run completes successfully.

Causes Link 0 to delete scratch files at the end of a run, including any files that were named explicitly preceding this directive. In other words, if a file is named before %NoSave is encountered, it will not be saved. However, if the % directive naming the file appears after the %NoSave directive, the file will be retained.

If both %Save and %NoSave are specified, then the one appearing latest in the input file takes precedence.

%Subst LN dir
Tells Link 0 to take the executable (.exe file) for a link from an alternate directory. For example %SUBST L913 /user/chem will cause /user/chem/l913.exe to be run instead of the default executable (in $g09root). The directory specification should be in the usual format for the machine involved. Only the directory can be specified; the file name must have the standard form of lnnnn.exe, where nnnn is the Link number.


Requests that the job use up to N processors for shared memory parallel execution on SMP multiprocessor computers. This capability is only available on some computer systems. On parallel machines, the number of processors to use in production runs is usually set in the Default.Route file, and the %NProcShared Link 0 command is used to override this local default (e.g., to run debug jobs on a single processor even if the default is to use 4 processors). If %NProcShared is not used, and no default is provided in the Default.Route file, then only one processor is used.

The %NProc directive used in earlier program versions is obsolete.

%LindaWorkers=node1[:n1] [,node2[:n2]] …
This lists the TCP node name for each node to use. By default, one Linda worker is started on each node, but the optional value allows this to be varied. A worker is always started on the node where the job is started (the master node) whether or not it appears in the node list. %LindaWorkers may be combined with %NProcShared. In this case, one or more parallel worker processes will be run on each node (the number still determined by the values in %LindaWorkers). The value to %NProcShared specifies the number of SMP processors/cores to use on each system in the worker node list.

Do not use the obsolete %NProcLinda directive. G09 will compute the total number of Linda workers based on the %LindaWorkers input.

Start Linda workers using ssh rather than rsh.

Report details concerning the starting and stopping of Linda workers.


These commands specify a name for the checkpoint file, and an alternate name and directory location for the read-write file, and cause only the checkpoint file to be saved at the conclusion of the Gaussian job:

%RWF=/chem/scratch2/water  Files to be deleted go here.
%Chk=water                 Files to be saved go here.

The following directive causes a network parallel job to be run across the specified 5 nodes. Nodes hamlet and ophelia will each run two worker processes.


The following directives specify that a parallel job will be executed on hosts norway, italy and spain. Nodes norway and italy will each run one 4-way SMP parallel worker, and spain will run two such workers:

%NProcShared=4   Specifies four-way SMP parallelism.

These directives make sense when norway and italy are 4 processor/core computers, and spain is an 8 processor/core computer.


Last update: 28 May 2013