3 votes

Solve linear system for only part of the solution vector

The only way that I'm aware of to take advantage of only needing a partial solution is in the triangular solves. But those are usually a small part of the total time in dense LU (unless you have many ...
Neil Lindquist's user avatar
2 votes
Accepted

How to efficiently transpose distributed matrix in Scalapack?

Unfortunately there really is no efficient way to do it; transposing a matrix stored as a distributed object on a distributed memory machine is just inherently a bad thing to be doing as it ...
Ian Bush's user avatar
  • 591
2 votes

Benchmark problems for eigenvalue reordering algorithms sought

The question is quite old, but I can give a meaningful answer here. One of the most common algorithms to solve algebraic Riccati equations $A^TX+XA+Q=XGX$ (the Schur method) goes as follows: Compute ...
Federico Poloni's user avatar
1 vote

row and column based distributed LU factorization

The analysis for the 2d process or device grid case carries over to the 1d grid case, just set one of your dimensions to 1. However, using a 2d grid will scale significantly better. So, I'd recommend ...
Neil Lindquist's user avatar
1 vote

How to debug segmentation faults in large problems?

There were some hints above already that this may be an integer range problem. A 32 bit signed integer goes up to values of about 2e9. A 50k x 50k symmetric matrix lives in an array of size about ...
Carsten B.'s user avatar

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