Command line options

In this module you will learn how to use Yambo's command line options.

Prerequisites

Previous modules

• Initialization for bulk hBN.

You will need:

• The SAVE databases for bulk hBN
• The yambo executable

Uppercase options

Uppercase options modify some of the code's default settings. They can be used when launching the code but also when generating input files.

Allowed options

To see the list of options, do:

$ yambo -H
Tool: yambo 4.1.2 rev.14024
Description: A shiny pot of fun and happiness [C.D.Hogan] 
-J <opt>	:Job string identifier
-V <opt>	:Input file verbosity
                [opt=RL,kpt,sc,qp,io,gen,resp,all,par]
-F <opt>	:Input file
-I <opt>	:Core I/O directory
-O <opt>	:Additional I/O directory
-C <opt>	:Communications I/O directory
-D		:DataBases properties
-W <opt>	:Wall Time limitation (1d2h30m format)
-Q		:Don't launch the text editor
-M		:Switch-off MPI support (serial run)
-N		:Switch-off OpenMP support (single thread run)
[Lower case options]

Command line options are extremely important to master if you want to use yambo productively. Often, the meaning is clear from the help menu:

$ yambo -F yambo.in_HF -x    Make a Hartree -Fock input file called yambo.in_HF
$ yambo -D                   Summarize the content of the databases in the SAVE folder
$ yambo -I ../               Run the code, using a SAVE folder in a directory one level up
$ yambo -C MyTest            Run the code, putting all report, log, plot files inside a folder MyTest

Other options deserve a closer look.

Verbosity

Yambo uses many input variables, many of which can be left at their default values. To keep input files short and manageable, only a few variables appear by default in the inout file. More advanced variables can be switched on by using the -V verbosity option. These are grouped according to the type of variable. For instance, -V RL switches on variables related to G vector summations, and -V io switches on options related to I/O control. Try:

$ yambo -o c -V RL       switches on:
FFTGvecs=  3951        RL    # [FFT] Plane-waves

$ yambo -o c -V io       switches on:
StdoHash=  40                # [IO] Live-timing Hashes
DBsIOoff= "none"             # [IO] Space-separated list of DB with NO I/O. DB= ...
DBsFRAGpm= "none"            # [IO] Space-separated list of +DB to be FRAG and ...
#WFbuffIO                    # [IO] Wave-functions buffered I/O

Unfortunately, -V options must be invoked and changed one at a time. When you are more expert, you may go straight to -V all, which turns on all possible variables. However note that yambo -o c -V all adds an extra 30 variables to the input file, which can be confusing: use it with care.

Job script label

The best way to keep track of different runs using different parameters is through the -J flag. This inserts a label in all output and report files, and creates a new folder containing any new databases (i.e. they are not written in the core SAVE folder). Try:

$ yambo -J 1Ry -V RL -x        and modify to
FFTGvecs = 1 Ry
EXXGvecs = 1 Ry
$ yambo -J 1Ry           Run the code
$ ls
yambo.in SAVE  
o-1Ry.hf r-1Ry_HF_and_locXC 1Ry 1Ry/ndb.HF_and_locXC

This is extremely useful when running convergence tests, trying out different parameters, etc.

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