Re: [Libmesh-users] [RB] Time comparison between FE and RB methods

[David K. <dav...@ak...>]

Hello,

Yes, you can use the "libMesh Performance" output to see how long each type
of solve took. To get an RB solve time I would normally do an "online
stage" solve and look at the timing info for "rb_solve". To get an FE solve
time, you can look at the average time of a truth_solve, that should be
fine.

Note that the speedup you observe generally depends a lot on the details of
the problem, and is generally larger for problems with large FE meshes
(especially in 3D).

Best,
David


On Fri, Jun 8, 2018 at 1:18 AM, <ss...@pu...> wrote:

> Hello, all.
>
>
>
> I want to compare the computation time between FE and RB methods, so I
> looked at "libMesh Performance."
>
> Here, I used the "Avg Time with Sub" of "truth_solve()" as the FE solve
> time
> in the RB offline stage.
>
> And as the RB solve time, I used the "Avg Time with Sub" of "rb_solve()" in
> the RB online stage.
>
> But I don't know if these are right ways to compare computation times.
>
>
>
> Please tell me which values are generally used to compare computation times
> between FE and RB methods.
>
>
>
> For reference, results of "libMesh Performance" in my codes are as follows.
>
> (Offline stage)
>
>
>
> libMesh Performance: Alive time=1702.12, Active time=1692.06
>
> ------------------------------------------------------------
> ----------------
> -----------------------------------
>
> | Event                                                         nCalls
> Total Time         Avg Time         Total Time       Avg Time
> % of     Active Time       |
>
> |
> w/o Sub           w/o Sub           With Sub          With Sub        w/o S
> With S            |
>
> ------------------------------------------------------------
> ----------------
> -----------------------------------
>
> .
> |
>
> (skip)
> |
>
> .
> |
>
> | RBConstruction
> |
>
> |     add_scaled_matrix_and_vector()                63         16.6728
> 0.264648          37.1072           0.589003                0.99    2.19
> |
>
> |     clear()                                                 1
> 0.0356            0.035607         0.0356            0.035607
> 0.00    0.00                  |
>
> |     compute_Fq_representor_innerprods()      1           0.0161
> 0.016134         2.9970            2.997019             0.00    0.18
> |
>
> |     compute_max_error_bound()                   17         0.0722
> 0.004249         201.1186         11.830503             0.00    11.89
> |
>
> |     enrich_RB_space()                                16         0.6050
> 0.037811         0.6050            0.037811            0.04    0.04
> |
>
> |     train_reduced_basis()                              1           0.0032
> 0.003184         1661.9738       1661.973753            0.00     98.22
> |
>
> |     truth_assembly()                                     16
> 40.6187           2.538670         40.6187           2.538670
> 2.40    2.40                 |
>
> |     truth_solve()                                           16
> 0.0534              0.003335         92.7523           5.797018
> 0.00      5.48                 |
>
> |     update_RB_system_matrices()                 16         41.3210
> 2.582562         41.3210           2.582562                2.44      2.44
> |
>
> |     update_residual_terms()                          16         1222.1235
> 76.382721       1323.1667         82.697919               72.23    78.20
> |
>
> .
> |
>
> (skip)
> |
>
> .
> |
>
> ------------------------------------------------------------
> ----------------
> -----------------------------------
>
> (Online stage)
>
>
>
> libMesh Performance: Alive time=3.62904, Active time=2.99889
>
> ------------------------------------------------------------
> ----------------
> -----------------------------------
>
> | Event                                                         nCalls
> Total Time         Avg Time         Total Time       Avg Time
> % of     Active Time       |
>
> |
> w/o Sub           w/o Sub           With Sub          With Sub        w/o S
> With S            |
>
> ------------------------------------------------------------
> ----------------
> -----------------------------------
>
> .
> |
>
> (skip)
> |
>
> .
> |
>
> | RBEvaluation
> |
>
> |     clear()                                                   1
> 0.0002           0.000194         0.0002            0.000194
> 0.01     0.01                |
>
> |     compute_residual_dual_norm()                1          0.1543
> 0.154302         0.1543            0.154302                5.15     5.15
> |
>
> |     legacy_read_offline_data_from_files()       1          0.0218
> 0.021824         0.0247            0.024672                0.73     0.82
> |
>
> |     rb_solve()                                              1
> 0.0002           0.000175         0.1545            0.154478
> 0.01     5.15                |
>
> |     read_in_basis_functions()                        1          0.0000
> 0.000005         0.3755            0.375475                0.00     12.52
> |
>
> |     read_in_vectors_from_multiple_files()        1          0.0706
> 0.070551         0.3755            0.375469                2.35     12.52
> |
>
> |     resize_data_structures()                          1          0.0028
> 0.002847         0.0028            0.002847                0.09     0.09
> |
>
> .
> |
>
> (skip)
> |
>
> .
> |
>
> ------------------------------------------------------------
> ----------------
> -----------------------------------
>
>
>
> I look forward to your reply.
>
>
>
> Thank you.
>
>
>
> Regards,
>
> SKang
>
>
>
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