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dsuess / mpnum

Matrix Product Representation library for Python
BSD 3-Clause "New" or "Revised" License
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Fix mpnum.special.sumup #27

Closed dsuess closed 7 years ago

dsuess commented 7 years ago

The current implementation of mpnum.special.sumup is probably not the best. [1, Eq. (153)] suggests a more efficient algorithm for compression after summation. We should try it out.

[1] U. Schollwöck, “The density-matrix renormalization group in the age of matrix product states,” Annals of Physics, vol. 326, no. 1, pp. 96–192, Jan. 2011.

dsuess commented 7 years ago

Fixed in fc30ef3.

It's not exactly the sweeping-based solution proposed in [1], but it accomplishes a good scaling by using sparse matrices and (possibly) randomized truncated SVDs.