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Fabien Péan
2023-08-12 12:39:18 +02:00
committed by Franck HOUSSEN
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@@ -343,6 +343,13 @@ Note: Make sure to update `CMAKE_MODULE_PATH` env variable (otheriwse, `find_pac
You need to copy this eigen vector estimate in `v` (not `resid`) and set `info` to 1 before calling aupd methods.
The `v` vector targets a non-null vector such that `resid = 0`, that is, such that `A*v = lambda*v`.
- Using PARPACK, I get incorrect eigen values.
Make sure each MPI processor handles a subpart of the eigen system (matrices) only.
ARPACK handles and solves the whole eigen problem (matrices) at once.
PARPACK doesn't: each MPI processor must handle and solve a subpart of the eigen system (matrices) only (independently from the other processors).
See examples for Fortran in folder `PARPACK/EXAMPLES/MPI`, and for C/C++ examples in `PARPACK/TESTS/MPI/icb_parpack_c.c` and `PARPACK/TESTS/MPI/icb_parpack_cpp.cpp`
## Using MKL instead of BLAS / LAPACK
How to use arpack-ng with Intel MKL: