OPT_ADAM

	This is part of the ves module
	It is only available if you configure PLUMED with ./configure –enable-modules=ves . Furthermore, this feature is still being developed so take care when using it and report any problems on the mailing list.

Adaptive moment estimation (ADAM) optimizer.

Attention

This optimizer is still experimental and not fully documented. The syntax might change. Restarting does not work. We recommend to use the averaged stochastic gradient decent optimizer (OPT_AVERAGED_SGD) for now.

Examples

Glossary of keywords and components

Description of components

By default the value of the calculated quantity can be referenced elsewhere in the input file by using the label of the action. Alternatively this Action can be used to calculate the following quantities by employing the keywords listed below. 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	Keyword	Description
gradrms	MONITOR_INSTANTANEOUS_GRADIENT	the root mean square value of the coefficient gradient. For multiple biases this component is labeled using the number of the bias as gradrms-#.
gradmax	MONITOR_INSTANTANEOUS_GRADIENT	the largest absolute value of the coefficient gradient. For multiple biases this component is labeled using the number of the bias as gradmax-#.

Compulsory keywords

BIAS	the label of the VES bias to be optimized
STRIDE	the frequency of updating the coefficients given in the number of MD steps.
COEFFS_FILE	( default=coeffs.data ) the name of output file for the coefficients
COEFFS_OUTPUT	( default=100 ) how often the coefficients should be written to file. This parameter is given as the number of iterations.
STEPSIZE	the step size used for the optimization

Options

MONITOR_INSTANTANEOUS_GRADIENT	( default=off ) if quantities related to the instantaneous gradient should be outputted.
MULTIPLE_WALKERS	( default=off ) if optimization is to be performed using multiple walkers connected via MPI
AMSGRAD	( default=off ) Use the AMSGrad variant
COEFFS_FMT	specify format for coefficient file(s) (useful for decrease the number of digits in regtests)
COEFFS_SET_ID_PREFIX	suffix to add to the filename given in FILE to identify the bias, should only be given if a single filename is given in FILE when optimizing multiple biases.
INITIAL_COEFFS	the name(s) of file(s) with the initial coefficients
TARGETDIST_AVERAGES_FILE	the name of output file for the target distribution averages. By default it is targetdist-averages.data.
TARGETDIST_AVERAGES_OUTPUT	how often the target distribution averages should be written out to file. Note that the value is given in terms of coefficient iterations. If no value is given are the averages only written at the beginning of the optimization
BIAS_OUTPUT	how often the bias(es) should be written out to file. Note that the value is given in terms of coefficient iterations.
FES_OUTPUT	how often the FES(s) should be written out to file. Note that the value is given in terms of coefficient iterations.
FES_PROJ_OUTPUT	how often the projections of the FES(s) should be written out to file. Note that the value is given in terms of coefficient iterations.
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
MASK_FILE	read in a mask file which allows one to employ different step sizes for different coefficients and/or deactivate the optimization of certain coefficients (by putting values of 0.0). One can write out the resulting mask by using the OUTPUT_MASK_FILE keyword.
OUTPUT_MASK_FILE	Name of the file to write out the mask resulting from using the MASK_FILE keyword. Can also be used to generate a template mask file.
TARGETDIST_STRIDE	stride for updating a target distribution that is iteratively updated during the optimization. Note that the value is given in terms of coefficient iterations.
TARGETDIST_OUTPUT	how often the dynamic target distribution(s) should be written out to file. Note that the value is given in terms of coefficient iterations.
TARGETDIST_PROJ_OUTPUT	how often the projections of the dynamic target distribution(s) should be written out to file. Note that the value is given in terms of coefficient iterations.
BETA_1	Parameter for the first moment estimate. Defaults to 0.9
BETA_2	Parameter for the second moment estimate. Defaults to 0.999
EPSILON	Small parameter to avoid division by zero. Defaults to 1e-8
ADAMW_WEIGHT_DECAY	Weight decay parameter for the AdamW variant. Defaults to 0