RESCALE
This is part of the isdb module

Scales the value of an another action, being a Collective Variable or a Bias.

The rescaling factor is determined by a parameter defined on a logarithmic grid of dimension NBIN in the range from 1 to MAX_RESCALE. The current value of the rescaling parameter is stored and shared across other actions using a SELECTOR. A Monte Carlo procedure is used to update the value of the rescaling factor every MC_STRIDE steps of molecular dynamics. Well-tempered metadynamics, defined by the parameters W0 and BIASFACTOR, is used to enhance the sampling in the space of the rescaling factor. The well-tempered metadynamics bias potential is written to the file BFILE every BSTRIDE steps and read when restarting the simulation using the directive RESTART.

Note
Additional arguments not to be scaled, one for each bin in the rescaling parameter ladder, can be provided at the end of the ARG list. The number of such arguments is specified by the option NOT_RESCALED. These arguments will be not be scaled, but they will be considered as bias potentials and used in the computation of the Metropolis acceptance probability when proposing a move in the rescaling parameter. See example below.
If PLUMED is running in a multiple-replica framework (for example using the -multi option in GROMACS), the arguments will be summed across replicas, unless the NOT_SHARED option is used. Also, the value of the SELECTOR will be shared and thus will be the same in all replicas.
Examples

In this example we use RESCALE to implement a simulated-tempering like approach. The total potential energy of the system is scaled by a parameter defined on a logarithmic grid of 5 bins in the range from 1 to 1.5. A well-tempered metadynamics bias potential is used to ensure diffusion in the space of the rescaling parameter.

Click on the labels of the actions for more information on what each action computes
tested on master
ene: ENERGY 
SELECTOR 
NAME
compulsory keyword name of the SELECTOR
=GAMMA
VALUE
compulsory keyword set (initial) value of the SELECTOR
=0 res: RESCALE ...
ARG
the input for this action is the scalar output from one or more other actions.
=ene
TEMP
compulsory keyword temperature
=300
SELECTOR
compulsory keyword name of the SELECTOR used for rescaling
=GAMMA
MAX_RESCALE
compulsory keyword maximum values for rescaling
=1.5
NBIN
compulsory keyword number of bins for gamma grid
=5
W0
could not find this keyword
=1000
BIASFACTOR
compulsory keyword bias factor
=100.0
BSTRIDE
compulsory keyword stride for writing bias
=2000
BFILE
compulsory keyword file name for bias
=bias.dat ... PRINT
FILE
the name of the file on which to output these quantities
=COLVAR
ARG
the input for this action is the scalar output from one or more other actions.
=*
STRIDE
compulsory keyword ( default=1 ) the frequency with which the quantities of interest should be output
=100

In this second example, we add to the simulated-tempering approach introduced above one Parallel Bias metadynamics simulation (see PBMETAD) for each value of the rescaling parameter. At each moment of the simulation, only one of the PBMETAD actions is activated, based on the current value of the associated SELECTOR. The PBMETAD bias potentials are not scaled, but just used in the calculation of the Metropolis acceptance probability when proposing a move in the rescaling parameter.

Click on the labels of the actions for more information on what each action computes
tested on master
ene: ENERGY 
d: DISTANCE 
ATOMS
the pair of atom that we are calculating the distance between.
=1,2 SELECTOR
NAME
compulsory keyword name of the SELECTOR
=GAMMA
VALUE
compulsory keyword set (initial) value of the SELECTOR
=0 pbmetad0: PBMETAD
ARG
the input for this action is the scalar output from one or more other actions.
=d
SELECTOR
add forces and do update based on the value of SELECTOR
=GAMMA
SELECTOR_ID
value of SELECTOR
=0
SIGMA
compulsory keyword the widths of the Gaussian hills
=0.1
PACE
compulsory keyword the frequency for hill addition, one for all biases
=500
HEIGHT
the height of the Gaussian hills, one for all biases.
=1
BIASFACTOR
use well tempered metadynamics with this bias factor, one for all biases.
=8
FILE
files in which the lists of added hills are stored, default names are assigned using arguments if FILE is not found
=HILLS.0 pbmetad1: PBMETAD
ARG
the input for this action is the scalar output from one or more other actions.
=d
SELECTOR
add forces and do update based on the value of SELECTOR
=GAMMA
SELECTOR_ID
value of SELECTOR
=1
SIGMA
compulsory keyword the widths of the Gaussian hills
=0.1
PACE
compulsory keyword the frequency for hill addition, one for all biases
=500
HEIGHT
the height of the Gaussian hills, one for all biases.
=1
BIASFACTOR
use well tempered metadynamics with this bias factor, one for all biases.
=8
FILE
files in which the lists of added hills are stored, default names are assigned using arguments if FILE is not found
=HILLS.1 pbmetad2: PBMETAD
ARG
the input for this action is the scalar output from one or more other actions.
=d
SELECTOR
add forces and do update based on the value of SELECTOR
=GAMMA
SELECTOR_ID
value of SELECTOR
=2
SIGMA
compulsory keyword the widths of the Gaussian hills
=0.1
PACE
compulsory keyword the frequency for hill addition, one for all biases
=500
HEIGHT
the height of the Gaussian hills, one for all biases.
=1
BIASFACTOR
use well tempered metadynamics with this bias factor, one for all biases.
=8
FILE
files in which the lists of added hills are stored, default names are assigned using arguments if FILE is not found
=HILLS.2 pbmetad3: PBMETAD
ARG
the input for this action is the scalar output from one or more other actions.
=d
SELECTOR
add forces and do update based on the value of SELECTOR
=GAMMA
SELECTOR_ID
value of SELECTOR
=3
SIGMA
compulsory keyword the widths of the Gaussian hills
=0.1
PACE
compulsory keyword the frequency for hill addition, one for all biases
=500
HEIGHT
the height of the Gaussian hills, one for all biases.
=1
BIASFACTOR
use well tempered metadynamics with this bias factor, one for all biases.
=8
FILE
files in which the lists of added hills are stored, default names are assigned using arguments if FILE is not found
=HILLS.3 pbmetad4: PBMETAD
ARG
the input for this action is the scalar output from one or more other actions.
=d
SELECTOR
add forces and do update based on the value of SELECTOR
=GAMMA
SELECTOR_ID
value of SELECTOR
=4
SIGMA
compulsory keyword the widths of the Gaussian hills
=0.1
PACE
compulsory keyword the frequency for hill addition, one for all biases
=500
HEIGHT
the height of the Gaussian hills, one for all biases.
=1
BIASFACTOR
use well tempered metadynamics with this bias factor, one for all biases.
=8
FILE
files in which the lists of added hills are stored, default names are assigned using arguments if FILE is not found
=HILLS.4 res: RESCALE ...
TEMP
compulsory keyword temperature
=300
ARG
the input for this action is the scalar output from one or more other actions.
=ene,pbmetad0.bias,pbmetad1.bias,pbmetad2.bias,pbmetad3.bias,pbmetad4.bias
SELECTOR
compulsory keyword name of the SELECTOR used for rescaling
=GAMMA
MAX_RESCALE
compulsory keyword maximum values for rescaling
=1.5
NOT_RESCALED
these last N arguments will not be scaled
=5
NBIN
compulsory keyword number of bins for gamma grid
=5
W0
could not find this keyword
=1000
BIASFACTOR
compulsory keyword bias factor
=100.0
BSTRIDE
compulsory keyword stride for writing bias
=2000
BFILE
compulsory keyword file name for bias
=bias.dat ... PRINT
FILE
the name of the file on which to output these quantities
=COLVAR
ARG
the input for this action is the scalar output from one or more other actions.
=*
STRIDE
compulsory keyword ( default=1 ) the frequency with which the quantities of interest should be output
=100
Glossary of keywords and components
Description of components

By default this Action calculates the following quantities. These quantities can be referenced elsewhere in the input by using this Action's label followed by a dot and the name of the quantity required from the list below.

Quantity Description
bias the instantaneous value of the bias potential
igamma gamma parameter
accgamma MC acceptance for gamma
wtbias well-tempered bias
Compulsory keywords
TEMP temperature
SELECTOR name of the SELECTOR used for rescaling
MAX_RESCALE maximum values for rescaling
NBIN number of bins for gamma grid
W0 initial bias height
BIASFACTOR bias factor
BSTRIDE stride for writing bias
BFILE file name for bias
Options
NUMERICAL_DERIVATIVES

( default=off ) calculate the derivatives for these quantities numerically

ARG the input for this action is the scalar output from one or more other actions. The particular scalars that you will use are referenced using the label of the action. If the label appears on its own then it is assumed that the Action calculates a single scalar value. The value of this scalar is thus used as the input to this new action. If * or *.* appears the scalars calculated by all the proceeding actions in the input file are taken. Some actions have multi-component outputs and each component of the output has a specific label. For example a DISTANCE action labelled dist may have three components x, y and z. To take just the x component you should use dist.x, if you wish to take all three components then use dist.*.More information on the referencing of Actions can be found in the section of the manual on the PLUMED Getting Started. Scalar values can also be referenced using POSIX regular expressions as detailed in the section on Regular Expressions. To use this feature you you must compile PLUMED with the appropriate flag. You can use multiple instances of this keyword i.e. ARG1, ARG2, ARG3...
NOT_SHARED list of arguments (from 1 to N) not summed across replicas
NOT_RESCALED these last N arguments will not be scaled
MC_STEPS number of MC steps
MC_STRIDE MC stride
PACE Pace for adding bias, in MC stride unit