# Something went wrong with the same card on different computers

**URL:** <https://openmc.discourse.group/t/something-went-wrong-with-the-same-card-on-different-computers/2574>\
**Category:** User Support\
**Created:** [December 17, 2022, 5:45am UTC](https://openmc.discourse.group/t/something-went-wrong-with-the-same-card-on-different-computers/2574 "2022-12-17T05:45:57Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Jacob](https://avatars.discourse-cdn.com/v4/letter/j/f1d935/32.png) [@Jacob](https://openmc.discourse.group/u/Jacob)\
**Post date:** [December 17, 2022, 5:45am UTC](https://openmc.discourse.group/t/something-went-wrong-with-the-same-card-on-different-computers/2574/1 "2022-12-17T05:45:57Z")

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Hello!

I just run the same input card on the different computers, and the version of the OpenMC is 0.13.0 and 0.13.2, respectively. But the combined Keff result of the version 0.13.0 is 0.21117 and the other one is 0.27375. So this is why, is there anything related to the calculating performance of the computer?

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**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\
**Post date:** [December 31, 2022, 4:57am UTC](https://openmc.discourse.group/t/something-went-wrong-with-the-same-card-on-different-computers/2574/2 "2022-12-31T04:57:52Z")

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@Jacob Without knowing anything about you problem, it’s hard to say what this could be. My first question to you is: have you looked at the uncertainties on the reported k-eff values? That is, are the differences statistically significant? If you have a model/script you can share that demonstrates this problem, that would allow someone here to look into it further.

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**Author:** ![Jacob](https://avatars.discourse-cdn.com/v4/letter/j/f1d935/32.png) [@Jacob](https://openmc.discourse.group/u/Jacob)\
**Post date:** [January 7, 2023, 9:05am UTC](https://openmc.discourse.group/t/something-went-wrong-with-the-same-card-on-different-computers/2574/3 "2023-01-07T09:05:59Z")

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Hello! @paulromano

This is the source of the input card:

> <https://github.com/openmc-dev/openmc-notebooks/blob/main/unstructured-mesh-part-i.ipynb>

**The result of the input card on the Github is here:**

The OpenMC Monte Carlo Code  
Copyright | 2011-2022 MIT, UChicago Argonne LLC, and contributors  
License | [License Agreement — OpenMC Documentation](https://docs.openmc.org/en/latest/license.html)  
Version | 0.13.1  
Git SHA1 | 33bc948f4b855c037975f16d16091fe4ecd12de3  
Date/Time | 2022-10-05 21:41:46  
MPI Processes | 1  
OpenMP Threads | 2

Reading settings XML file…  
Reading cross sections XML file…  
Reading materials XML file…  
Reading geometry XML file…  
Reading U234 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/U234.h5  
Reading U235 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/U235.h5  
Reading U238 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/U238.h5  
Reading O16 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/O16.h5  
Reading Zr90 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/Zr90.h5  
Reading Zr91 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/Zr91.h5  
Reading Zr92 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/Zr92.h5  
Reading Zr94 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/Zr94.h5  
Reading Zr96 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/Zr96.h5  
Reading H1 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/H1.h5  
Reading B10 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/B10.h5  
Reading B11 from /home/pshriwise/data/xs/openmc/nndc\_hdf5/B11.h5  
Reading c\_H\_in\_H2O from /home/pshriwise/data/xs/openmc/nndc\_hdf5/c\_H\_in\_H2O.h5  
Minimum neutron data temperature: 294 K  
Maximum neutron data temperature: 294 K  
Preparing distributed cell instances…  
Reading plot XML file…  
Writing summary.h5 file…  
Maximum neutron transport energy: 20000000 eV for U235  
Initializing source particles…

====================\> K EIGENVALUE SIMULATION \<====================

Bat./Gen. k Average k  
========= ======== ====================  
1/1 0.30539  
2/1 0.26134  
3/1 0.22212  
4/1 0.22179  
5/1 0.14131  
6/1 0.21170  
7/1 0.16877 0.19024 +/- 0.02146  
8/1 0.19222 0.19090 +/- 0.01241  
9/1 0.17863 0.18783 +/- 0.00930  
10/1 0.21289 0.19284 +/- 0.00877  
Creating state point statepoint.10.h5…

=======================\> TIMING STATISTICS \<=======================

Total time for initialization = 3.3074e-01 seconds  
Reading cross sections = 3.2297e-01 seconds  
Total time in simulation = 1.0950e-02 seconds  
Time in transport only = 1.0091e-02 seconds  
Time in inactive batches = 5.4269e-03 seconds  
Time in active batches = 5.5232e-03 seconds  
Time synchronizing fission bank = 5.0570e-05 seconds  
Sampling source sites = 3.8890e-05 seconds  
SEND/RECV source sites = 6.5900e-06 seconds  
Time accumulating tallies = 1.0400e-06 seconds  
Time writing statepoints = 7.5274e-04 seconds  
Total time for finalization = 1.7600e-06 seconds  
Total time elapsed = 3.4390e-01 seconds  
Calculation Rate (inactive) = 92133.3 particles/second  
Calculation Rate (active) = 90527.9 particles/second

============================\> RESULTS \<============================

k-effective (Collision) = 0.19269 +/- 0.01294  
k-effective (Track-length) = 0.19284 +/- 0.00877  
k-effective (Absorption) = 0.24164 +/- 0.01373  
Combined k-effective = 0.21117 +/- 0.00443  
Leakage Fraction = 0.81400 +/- 0.01122

**And this is my result:**

The OpenMC Monte Carlo Code  
Copyright | 2011-2022 MIT, UChicago Argonne LLC, and contributors  
License | [License Agreement — OpenMC Documentation](https://docs.openmc.org/en/latest/license.html)  
Version | 0.13.2  
Git SHA1 | 63f1fa44c0601cf8a717db5583e82b3d50e04d1f  
Date/Time | 2023-01-03 18:12:58  
MPI Processes | 1  
OpenMP Threads | 4

Reading settings XML file…  
Reading cross sections XML file…  
Reading materials XML file…  
Reading geometry XML file…  
Reading U234 from /home/。。/endfb-viii.0-hdf5/neutron/U234.h5  
Reading U235 from /home/。。/endfb-viii.0-hdf5/neutron/U235.h5  
Reading U238 from /home/。。/endfb-viii.0-hdf5/neutron/U238.h5  
Reading O16 from /home/。。/endfb-viii.0-hdf5/neutron/O16.h5  
Reading Zr90 from /home/。。/endfb-viii.0-hdf5/neutron/Zr90.h5  
Reading Zr91 from /home/。。/endfb-viii.0-hdf5/neutron/Zr91.h5  
Reading Zr92 from /home/。。/endfb-viii.0-hdf5/neutron/Zr92.h5  
Reading Zr94 from /home/。。/endfb-viii.0-hdf5/neutron/Zr94.h5  
Reading Zr96 from /home/。。/endfb-viii.0-hdf5/neutron/Zr96.h5  
WARNING: Negative value(s) found on probability table for nuclide Zr96 at 294K  
Reading H1 from /home/。。/endfb-viii.0-hdf5/neutron/H1.h5  
Reading B10 from /home/。。/endfb-viii.0-hdf5/neutron/B10.h5  
Reading B11 from /home/。。/endfb-viii.0-hdf5/neutron/B11.h5  
Reading c\_H\_in\_H2O from /home/。。/endfb-viii.0-hdf5/neutron/c\_H\_in\_H2O.h5  
Minimum neutron data temperature: 294 K  
Maximum neutron data temperature: 294 K  
Reading tallies XML file…  
Preparing distributed cell instances…  
Reading plot XML file…  
Writing summary.h5 file…  
Maximum neutron transport energy: 20000000 eV for Zr90  
Initializing source particles…

====================\> K EIGENVALUE SIMULATION \<====================

Bat./Gen. k Average k  
========= ======== ====================  
1/1 0.26116  
2/1 0.23484  
3/1 0.27700  
4/1 0.16372  
5/1 0.29024  
6/1 0.16335  
7/1 0.32487 0.24411 +/- 0.08076  
8/1 0.21856 0.23560 +/- 0.04740  
9/1 0.16202 0.21720 +/- 0.03823  
10/1 0.23567 0.22089 +/- 0.02984  
Creating state point statepoint.10.h5…  
WARNING: Output for a MOAB mesh (mesh 1) was requested but will not be written.  
Please use the Python API to generated the desired VTK tetrahedral  
mesh.

=======================\> TIMING STATISTICS \<=======================

Total time for initialization = 2.5415e+02 seconds  
Reading cross sections = 1.0766e+01 seconds  
Total time in simulation = 5.0045e-01 seconds  
Time in transport only = 5.9375e-02 seconds  
Time in inactive batches = 2.6384e-02 seconds  
Time in active batches = 4.7406e-01 seconds  
Time synchronizing fission bank = 1.4183e-04 seconds  
Sampling source sites = 1.0218e-04 seconds  
SEND/RECV source sites = 8.8750e-06 seconds  
Time accumulating tallies = 3.7546e-03 seconds  
Time writing statepoints = 4.3656e-01 seconds  
Total time for finalization = 9.6627e-01 seconds  
Total time elapsed = 2.5563e+02 seconds  
Calculation Rate (inactive) = 18950.6 particles/second  
Calculation Rate (active) = 1054.71 particles/second

============================\> RESULTS \<============================

k-effective (Collision) = 0.23887 +/- 0.02017  
k-effective (Track-length) = 0.22089 +/- 0.02984  
k-effective (Absorption) = 0.24047 +/- 0.02812  
Combined k-effective = 0.27375 +/- 0.01088  
Leakage Fraction = 0.79800 +/- 0.03338

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**Author:** ![Shengli](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@Shengli](https://openmc.discourse.group/u/Shengli)\
**Post date:** [July 7, 2023, 8:29am UTC](https://openmc.discourse.group/t/something-went-wrong-with-the-same-card-on-different-computers/2574/4 "2023-07-07T08:29:24Z")

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Do you find the reason for such difference?  
We met a similar problem. A test case run with 0.13.0 (PC1), 0.13.2 (PC1), 0.13.0-dev (PC2), and 0.13.4-dev (PC2), 0.13.0-dev has keff ~200 pcm (vs ~10 pcm uncertainty) lower than other three.

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**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\
**Post date:** [July 10, 2023, 9:41pm UTC](https://openmc.discourse.group/t/something-went-wrong-with-the-same-card-on-different-computers/2574/5 "2023-07-10T21:41:42Z")

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Looking at the @Jacob’s output above, it looks like the k-effective values themselves have very high uncertainties, indicating that more batches/particles are needed in order to get a better comparison.

For your case @Shengli, there have been numerous bug fixes since 0.13.0 so it’s hard to say what exactly caused your results to be changed between that and the more recent versions. If you are getting consistent answers with recent versions of OpenMC, I would probably trust those.