Besides, the Trilinos direct solver applied is Amesos_Lapack(a mistake).
Changing to Klu therefore save more time.
在2022年10月19日星期三 UTC+8 20:30:53 写道：
> I run both matrix-based and matrix-free mode with release mode, both speed
> up a lot. The matrix-free CG iteration speeds up 30 times compared
Dear Wayne,
For performance it certainly matters, because some components of our
codes have more low-level checks in debug mode than others, and because
the compiler optimizations do not have the same effect on all parts of
our code. Make sure to test the release mode and see if it makes more
Thanks Martin !
I never considered about Debug or optimized mode before. Cmake result says
I'm using Debug mode.
Some more information: The computaiton is done in deal.ii 9.4.0 oracle
virtualBox, with 1 mpi process in qtcreator, and CPU is intel 10600kf. I
didn't change the CMakeLists and just
Dear Wayne,
I am a bit surprised by your numbers and find them rather high, at least
with the chosen problem sizes. I would expect the matrix-free solver to
run in less than a second for 111,000 unknowns on typical computers, not
almost 10 seconds. I need to honestly say that I do not have a g
Thanks for your reply Peter,
The matrix-free run is basic same as in step-75 except I substitute coarse
grid solver. For fe_degree=6 without GMG and fe_degree in each level
decrease by 1 for pMG, the solve_system() function runtime is 24.1s. It's
decomposed to *MatrixFree MG operators construct
Hi Wayne,
your numbers make totally sense. Don't forget that you are running for high
order: degree=6! The number of non-zeroes per element-stiffness matrix is
((degree + 1)^dim)^2 and the cost of computing the element stiffness matrix
is even ((degree + 1)^dim)^3 if I am not mistaken (3 nested
