PRINT

This is part of the generic module

Print quantities to a file.

This directive can be used multiple times in the input so you can print files with different strides or print different quantities to different files. You can control the buffering of output using the FLUSH keyword. Output file is either appended or backed up depending on the presence of the RESTART action. A per-action RESTART keyword can be used as well.

Notice that printing happens in the so-called "update" phase. This implies that printing is affected by the presence of UPDATE_IF actions. In addition, one might decide to start and stop printing at preassigned values of time using the UPDATE_FROM and UPDATE_UNTIL keywords. Keep into account that even on steps when the action is not updated (and thus the file is not printed) the argument will be activated. In other words, if you use UPDATE_FROM to start printing at a given time, the collective variables this PRINT statement depends on will be computed also before that time.

Examples

The following input instructs plumed to print the distance between atoms 3 and 5 on a file called COLVAR every 10 steps, and the distance and total energy on a file called COLVAR_ALL every 1000 steps.

Click on the labels of the actions for more information on what each action computes

# compute distance:
distance: DISTANCE 
ATOMS
the pair of atom that we are calculating the distance between. 
=2,5 The DISTANCE action with label distance calculates a single scalar value
# compute total energy (potential)
energy: ENERGY The ENERGY action with label energy calculates a single scalar value
# print distance on a file
PRINT 
ARG
compulsory keyword 
the labels of the values that you would like to print to the file 
=distance 
STRIDE
compulsory keyword ( default=1 )
the frequency with which the quantities of interest should be output 
=10 
FILE
the name of the file on which to output these quantities 
=COLVAR The PRINT action with label 
# print both variables on another file
PRINT 
ARG
compulsory keyword 
the labels of the values that you would like to print to the file 
=distance,energy 
STRIDE
compulsory keyword ( default=1 )
the frequency with which the quantities of interest should be output 
=1000 
FILE
the name of the file on which to output these quantities 
=COLVAR_ALL The PRINT action with label 

Notice that DISTANCE and ENERGY are computed respectively every 10 and 1000 steps, that is only when required.

Glossary of keywords and components

Compulsory keywords

ARG	the labels of the values that you would like to print to the file
STRIDE	( default=1 ) the frequency with which the quantities of interest should be output

Options

FILE	the name of the file on which to output these quantities
FMT	the format that should be used to output real numbers
RESTART	allows per-action setting of restart (YES/NO/AUTO)
UPDATE_FROM	Only update this action from this time
UPDATE_UNTIL	Only update this action until this time