[Nek5000-users] Problem in obtaining eigenvalues through Arnoldi (using NEK5000 with the ARPACK library)

Thu Jul 12 06:18:24 CDT 2018

I believe this extension is not part of Nek5000. You may want to contact the author directly.

Stefan

On 12 Jul 2018, at 10:10, "nek5000-users at lists.mcs.anl.gov <mailto:nek5000-users at lists.mcs.anl.gov> " <nek5000-users at lists.mcs.anl.gov <mailto:nek5000-users at lists.mcs.anl.gov> > wrote:

Hi Neks

    I am running a 3D simulation for a flow over a cylinder. My domain size for simulation is 100Dx100D. where D is the diameter of a cylinder. We have obtained the base flow through SFD. The base flow is used to calculate the stability analysis through NEK5000 with the ARPACK library (Implemented by A.  Peplinski).

we have used the following parameters.....

  90.0000     p111 : ARNOLDI: size of Krylov space
   30.0000     p112 : ARNOLDI: number of eigenvectors

We have run the Arnoldi with restart but we are not able to get the output file (eigenvalues.txt and egvext_cyl0.f0..) even after almost 20 restarts.
Also, we tried to run with increasing the size of Krylov space but the eigenvalues are not converging.

The log file shows no changes in converged ritz values after around 20-22 values.

The part of the log file is shown below...........

Kindly,  help me out and let me know where I am going wrong.....

Alok Mishra

---------------------------------------------------------------------------------------------------------------

ARNOLDI: after  520 stepper phase

 _naup2: Corresponding B-norm of the residual
 --------------------------------------------
    1 -    1:   6.623D-01

 _naup2: no. of "converged" Ritz values at this iter.
 ----------------------------------------------------
    1 -    1:    22

 _naup2: NEV and NP are
 ----------------------
    1 -    2:    52   128

 _naup2: "wanted" Ritz values -- real part
 -----------------------------------------
    1 -    5:   9.905D-01   9.905D-01   9.854D-01   9.854D-01   9.855D-01
    6 -   10:   9.855D-01   9.897D-01   9.897D-01   9.924D-01   9.930D-01
   11 -   15:   9.930D-01   9.905D-01   9.905D-01   9.943D-01   9.943D-01
   16 -   20:   9.938D-01   9.938D-01   9.948D-01   9.948D-01   9.949D-01
   21 -   25:   9.949D-01   9.951D-01   9.958D-01   9.960D-01   9.962D-01
   26 -   30:   9.962D-01   9.966D-01   9.970D-01   9.970D-01   9.969D-01
   31 -   35:   9.969D-01   9.973D-01   9.974D-01   9.975D-01   9.976D-01
   36 -   40:   9.976D-01   9.971D-01   9.971D-01   9.978D-01   9.979D-01
   41 -   45:   9.979D-01   9.982D-01   9.982D-01   1.000D+00   9.908D-01
   46 -   50:   9.908D-01   1.004D+00   1.004D+00   1.005D+00   1.005D+00
   51 -   52:   1.006D+00   1.006D+00

 _naup2: "wanted" Ritz values -- imag part
 -----------------------------------------
    1 -    5:   5.038D-02  -5.038D-02  -1.127D-01   1.127D-01  -1.119D-01
    6 -   10:   1.119D-01   6.954D-02  -6.954D-02   0.000D+00   3.705D-03
   11 -   15:  -3.705D-03  -7.103D-02   7.103D-02  -9.233D-04   9.233D-04
   16 -   20:   4.345D-02  -4.345D-02   6.799D-04  -6.799D-04  -1.821D-02
   21 -   25:   1.821D-02   0.000D+00   0.000D+00   0.000D+00  -2.047D-03
   26 -   30:   2.047D-03   0.000D+00   7.200D-05  -7.200D-05   2.386D-02
   31 -   35:  -2.386D-02   0.000D+00   0.000D+00   0.000D+00  -1.140D-04
   36 -   40:   1.140D-04   3.125D-02  -3.125D-02   0.000D+00  -1.248D-04
   41 -   45:   1.248D-04  -1.673D-03   1.673D-03   0.000D+00  -1.508D-01
   46 -   50:   1.508D-01  -1.863D-02   1.863D-02  -2.109D-02   2.109D-02
   51 -   52:  -1.152D-02   1.152D-02

 _naup2: Ritz estimates of the "wanted" values 
 ----------------------------------------------
    1 -    5:   3.315D-02   3.315D-02   3.244D-05   3.244D-05   7.035D-05
    6 -   10:   7.035D-05   6.072D-11   6.072D-11   1.314D-02   2.772D-06
   11 -   15:   2.772D-06   6.796D-15   6.796D-15   9.719D-04   9.719D-04
   16 -   20:   7.467D-17   7.467D-17   5.506D-04   5.506D-04   2.437D-16
   21 -   25:   2.437D-16   2.977D-03   7.238D-04   6.054D-04   3.914D-11
   26 -   30:   3.914D-11   1.827D-04   1.138D-04   1.138D-04   1.048D-16
   31 -   35:   1.048D-16   1.198D-04   6.358D-05   3.013D-05   3.490D-07
   36 -   40:   3.490D-07   9.960D-18   9.960D-18   1.340D-07   2.518D-10
   41 -   45:   2.518D-10   1.827D-16   1.827D-16   1.781D-16   7.278D-17
   46 -   50:   7.278D-17   0.000D+00   0.000D+00   0.000D+00   0.000D+00
   51 -   52:   0.000D+00   0.000D+00
   Reached max iteration number; settingido=-2 for checkpointing.
 ARNOLDI: 
 IDOARP  =           -2
 Writing checkpoint
       0      40 OPEN: ARPm11800.f00002
       0      40 OPEN: ARVm11800.f00002

       40  2.0000E-01 done :: Write checkpoint
                              file size =     621.E+00MB
                              avg data-throughput =   624.1MB/s
                              io-nodes =     1

  ARNOLDI: finalize
    Number of stepper cycles            520
    Time spent in ARNOLDI         60.3302609920502     
    Average stepper phase time    10.9141681075096     
 call outfld: ifpsco: F

       40  2.0000E-01 Write checkpoint:
       0      40 OPEN: m11800.f00001

       40  2.0000E-01 done :: Write checkpoint
                              file size =      4.0    MB
                              avg data-throughput =   303.2MB/s
                              io-nodes =     1

end of time-step loop

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