ML LSPARSDES

ML_LSPARSDES = [logical]
Default: ML_LSPARSDES = .FALSE. 

Description: Specifies whether angular-descriptor sparsification is enabled within the machine learning force field method.

Mind: This tag is only available as of VASP 6.4.3.

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This tag only works for ML_MODE=refit or reftbayesian!

To use the sparsification of angular descriptors set the following tags:

• ML_LSPARSDES=.TRUE..
• The ratio of the selected descriptors to the total number of descriptors: ML_RDES_SPARSDES. This tag controls the extent of the sparsification.
• The number of the highest eigenvalues $k$ to which the correlation is measured via the leverage scoring: ML_NRANK_SPARSDES. This parameter usually does not need to be changed.

We advise the user to adjust this parameter carefully and test it individually for each system. This means e.g. plotting the accuracy of the calculation against the computational speed (Pareto curves) for different values of ML_RDES_SPARSDES. The user can then choose a tradeoff between efficiency and accuracy. The behavior is system dependent, however, we have experienced the following trends for our test cases: For ML_DESC_TYPE=0 a descriptor sparsification of 50 percent ML_RDES_SPARSDES=0.5 leaves the accuracy almost untouched. If more spars descriptors are used such as e.g. ML_DESC_TYPE=1, which already contain much fewer descriptors than the standard descriptor ML_DESC_TYPE=0, a 50 percent sparsification for ML_DESC_TYPE=1 results in noticeable accuracy loss.

Related tags and articles

ML_LMLFF, ML_RDES_SPARSDES, ML_NRANK_SPARSDES, ML_DESC_TYPE

Examples that use this tag