# BICGstab error 20 years into nudged run

**URL:** <https://cms-helpdesk.ncas.ac.uk/t/bicgstab-error-20-years-into-nudged-run/1519>\
**Category:** Unified Model\
**Tags:** Monsoon2\
**Created:** [10 September 2024 14:51 UTC](https://cms-helpdesk.ncas.ac.uk/t/bicgstab-error-20-years-into-nudged-run/1519 "2024-09-10T14:51:31Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![mdalvi](https://avatars.discourse-cdn.com/v4/letter/m/ad7895/32.png) [@mdalvi](https://cms-helpdesk.ncas.ac.uk/u/mdalvi)\
**Post date:** [11 September 2024 09:32 UTC](https://cms-helpdesk.ncas.ac.uk/t/bicgstab-error-20-years-into-nudged-run/1519/4 "2024-09-11T09:32:22Z")

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Hi Isabelle,  
The script is not installed by default on Monsoon, so you will have to extract from the repository.  
$ mkdir ~/test (or suitable folder)  
$ cd ~/test/  
$ fcm export fcm:moci.xm\_tr/Utilities/lib/perturb\_theta.py  
$ chmod +x perturb\_theta.py  
$ cd cylc-run/u-df691/share/data/History\_Data/  
(assuming the atmos\_main task starting 01Dec2000 is failing)  
$ mv df691a.da20001201\_00 df691a.da20001201\_00.orig  
$ module load um\_tools  
$ ~/test/perturb\_theta.py df691a.da20001201\_00.orig --output ./df691a.da20001201\_00

Resubmit the failed task.

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