Introducing approximation into the MPS simulation method #475
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…_expectation_value
…arallelization in contract_2_dimensions
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@chriseclectic , I implemented the changes in MPS approximation as we discussed. |
atilag
previously approved these changes
Jun 8, 2020
chriseclectic
previously approved these changes
Jun 16, 2020
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@merav-aharoni Could you add a release note for this new feature? |
chriseclectic
added
the
Changelog: New Feature
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Added documentation for release notes. |
chriseclectic
approved these changes
Jun 17, 2020
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Summary
We allow using approximation when using the MPS simulation method.
Details and comments
The idea of approximation is to limit the number of Schmidt coefficients in the lambda matrices of the MPS. This can be done either by a size threshold or by the number of coefficients.
The approximation is controlled by two parameters at the beginning of svd.cpp:
APPROX_THRES- we discard values in lambda whose norm is smaller thanAPPROX_THRES * norm(S[0]), where S[0] is the largest Schmidt coefficient.
APPROX_LIMIT- we discard values only if the size of lambda is greater than this valueThese parameters are currently hard-coded, and for now can be changed only in the code.
We need to add a user interface for these parameters, and to experiment with this option.