@@ -39,6 +39,7 @@ The following parameters can be passed to `ActiveCalculator`
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```
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# inputs
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covariance: either a kernel or path to a saved/pickled model
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+ kernel_kw e.g. {'cutoff': 6.}
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calculator: any ASE calculator or SocketCalculator
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process_group: None or the value of mpi_init()
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meta: meta energy calculator for metadynamics
@@ -51,16 +52,11 @@ test: intervals for single point tests during MD
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# sampling and optimization
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ediff: energy sensitivity for sampling LCEs
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- ediff_tot: total energy sensitivity for sampling DFT data
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fdiff: forces sensitivity for sampling DFT data
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- noise_e: bias noise for total energies
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noise_f: bias noise for forces
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-
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- #
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- ignore_forces: dumps forces data from the regression
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```
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- #### covariance
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+ #### covariance, kernel_kw
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This parameter can be used for passing a kernel
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or a saved/pickled model to the calculator
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``` python
@@ -92,6 +88,9 @@ automatically saved and loaded in consecutive
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runs.
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If ` None ` , the default kernel will be used
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(see * Kernels* ) with an empty initial model.
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+ In that case ` kernel_kw ` can be used for
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+ passing some parameters (e.g. cutoff) to
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+ the kernel instantiation.
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#### calculator
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The main DFT calculator can which be any ASE
@@ -150,12 +149,11 @@ and the ML predictions will be saved in `'active_ML.traj'`.
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A single point calculation is triggered if ` test `
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steps have passed from the last one.
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- #### ediff, ediff_tot, fdiff
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+ #### ediff, fdiff
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These parameters control the sampling.
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` ediff ` is mainly used for sampling of the LCEs
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as the inducing data for the sparse representation.
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- ` ediff_tot ` and ` fdiff ` control the sampling
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- of DFT data.
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+ ` fdiff ` control the sampling of DFT data.
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The default parameters should be appropriate for
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starting the simulation.
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One can set ` fdiff ` equal to the desired accuracy
@@ -166,25 +164,18 @@ For global exploration, we recommend increasing the
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accuracy gradually/iteratively rather than choosing
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small values for these parameters from the beginning.
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- If ` ediff_tot=float('inf') ` , this parameter becomes
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- irrelevent, which might be the desired behaviour in
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- certain applications (similar for ` fdiff ` ).
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-
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- #### noise_e, noise_f
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- In optimization of hyper-parameters, the errors
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- (e.g. RMSE) are minimized towards these values.
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- They can be set to 0 for simple minimization of
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- RMSE but there is a chance for overfitting.
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- For instance choosing smaller ` noise_f ` may
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+ #### noise_f
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+ In optimization of hyper-parameters, the
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+ mean absolute error (MAE) of forces in fitting
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+ is tuned to this value: MAE$\sim$` noise_f ` .
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+ ` noise_f ` of 0 is also acceptable but
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+ there is a chance for overfitting.
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+ For instance during on-the-fly training,
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+ choosing smaller ` noise_f ` may
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cause more sampling of DFT data without a
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meaningful increase of the models accuracy.
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- The value of 0 maybe used for fitting a static
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- data set with a high accuracy.
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- For more control see the following options
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- * If noise_e = None -> noise_e = ediff_tot (<- default)
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- * If noise_e < 0 -> RMSE of energies is omitted from the loss function.
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- * If noise_f = None -> noise_f = fdiff (<- default)
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- * If noise_f < 0 -> RMSE of forces is omitted from the loss function.
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+ But the value of 0 maybe used for fitting a
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+ static data set whithout any issues.
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### Training with existing data
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If some DFT data already exists, one can train a
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