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Changes between Version 3 and Version 4 of Ticket #2699, comment 10


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Timestamp:
05/03/17 09:22:54 (8 years ago)
Author:
gkronber
Comment:

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  • Ticket #2699, comment 10

    v3 v4  
    11Review comments:
    2  * LINQ is used a lot in combination with matrix operations. This is often slow because of memory allocations required for enumerators. (DONE)
    3  * There should be an option to scale the input variables (scaling should be active by default) (DONE)
    4  * RBF regression does not support noise. If there are duplicate x vectors, model building fails. An option would be to add a diagonal matrix to the gram matrix (leading to kernel ridge regression?) (DONE)
    5  * I have not found a source for the calculation of variance and LOO error (DONE, removed LOO calculation)
    6  * Don't know how to best unify covariance functions and kernel functions (there is some duplication) (DONE).
    7  * The calculation of the covariance matrix takes a lot of time (10x longer than the equivalent calculation when using an equivalent covariance matrix). I suspect that the reason is the rather general implementation for distance calculation. (DONE)
    8  * Beta should be a parameter of the algorithm instead of the kernel to make it easier to run a grid test. (DONE)
    9  * Multiple of the implemented kernels are only conditionally positive definite. See http://num.math.uni-goettingen.de/schaback/teaching/sc.pdf for a definition of the kernels and valid beta-values. Additionally, it is necessary to extend the basis functions for these kernels depending on the value of beta.
     2 * ~~LINQ is used a lot in combination with matrix operations. This is often slow because of memory allocations required for enumerators.~~ (DONE)
     3 * ~~There should be an option to scale the input variables (scaling should be active by default)~~ (DONE)
     4 * ~~RBF regression does not support noise. If there are duplicate x vectors, model building fails. An option would be to add a diagonal matrix to the gram matrix (leading to kernel ridge regression?)~~ (DONE)
     5 * ~~I have not found a source for the calculation of variance and LOO error~~ (DONE, fixed LOO calculation based on GPML book)
     6 * ~~Don't know how to best unify covariance functions and kernel functions (there is some duplication)~~ (DONE, only use RBF 'kernels' with a beta parameter).
     7 * ~~The calculation of the covariance matrix takes a lot of time (10x longer than the equivalent calculation when using an equivalent covariance matrix). I suspect that the reason is the rather general implementation for distance calculation.~~ (DONE)
     8 * ~~Beta should be a parameter of the algorithm instead of the kernel to make it easier to run a grid test.~~ (DONE)
     9 * ~~Multiple of the implemented kernels are only conditionally positive definite. See http://num.math.uni-goettingen.de/schaback/teaching/sc.pdf for a definition of the kernels and valid beta-values. Additionally, it is necessary to extend the basis functions for these kernels depending on the value of beta.~~ (Handled, by trying to use Cholesky decompose first and if it fails trying to calculate the inverse via LU decomposition).
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