Difference between revisions of "FAQ"

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== How do I set up the libraries? ==
 
== How do I set up the libraries? ==
  
If you haven't already, please check out [[Getting_started#Compiling_libraries]].
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If you haven't already, please check out [[Getting_started#Libraries]].
 
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Sometimes the curl library is necessary, sometimes not.  Try commenting adding/commenting out -lcurl
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The necessity of some libraries appears to depend on distribution.
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Try commenting adding/commenting out  -lcurl and/or -lblas
  
 
== Where do I get initial conditions for a simulation? ==
 
== Where do I get initial conditions for a simulation? ==
 
The best initial condition is almost always to restart from a run with as similar parameters as possible.
 
The best initial condition is almost always to restart from a run with as similar parameters as possible.
See [[Database]].  
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Some states may be found in the [[Database]].  If you have already run some jobs, remember that their parameters are recorded in [[main.info]].
  
 
If such a state-file is not to hand, try <tt>utils/ic.f90</tt>.  Artificial initial conditions tend to suffer  
 
If such a state-file is not to hand, try <tt>utils/ic.f90</tt>.  Artificial initial conditions tend to suffer  
 
far greater transients.  Be prepared to use smaller timesteps and possible greater resolution to overcome the transient.
 
far greater transients.  Be prepared to use smaller timesteps and possible greater resolution to overcome the transient.
 
  
 
== My job isn't starting properly, what's wrong? ==
 
== My job isn't starting properly, what's wrong? ==
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If you see an error from <tt>tim_check_cgce</tt>, it's likely that either an inappropriate initial condition was used, or that the resolution was inadequate.
 
If you see an error from <tt>tim_check_cgce</tt>, it's likely that either an inappropriate initial condition was used, or that the resolution was inadequate.
  
Double-check all parameters were set correctly, try <tt>less main.info</tt>.  If you had a similar run that worked, check which parameters have changed: try e.g. <tt>diff main.info ../job005/main.info</tt>
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Double-check all parameters were set correctly, see the [[Main.info|main.info]] file.  If you had a similar run that worked, check which parameters have changed: try e.g. <tt>diff main.info ../job005/main.info</tt>
 
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== How do I select resolution? ==
 
== How do I select resolution? ==
 
Best to start from a similar job and to check one of the spectrum files, e.g. <tt>vel_spec0010.dat</tt>.  The values should fall by several orders, to approximately below <tt>1e-5</tt> in each dimension.
 
Best to start from a similar job and to check one of the spectrum files, e.g. <tt>vel_spec0010.dat</tt>.  The values should fall by several orders, to approximately below <tt>1e-5</tt> in each dimension.
 
  
 
== What is the spatial grid? ==
 
== What is the spatial grid? ==
<tt>i_N</tt> radial points are non-equispaced, bunched near the walls, and very slightly so at the axis to ensure spatial accuracy where fewer points are available for the banded matrices.  The points are equispaced in theta on <tt>3*i_M</tt> points and in z on <tt>3*i_K</tt> points.  The domain has length <tt>L=2.pi/d_alpha</tt>.
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<tt>i_N</tt> radial points are non-equispaced, bunched near the walls, and very slightly near the axis to ensure spatial accuracy where fewer points are available for the banded matrices.  The points are equispaced in theta on <tt>3*i_M</tt> points and in z on <tt>3*i_K</tt> points.  The domain has radius 1 and length <tt>L=2*pi/d_alpha</tt>.
  
 
== I get 'matrix inversion error 1' ==
 
== I get 'matrix inversion error 1' ==
 
An error in a #define prevented serial use with openpipeflow-1.10, which was a significant update to the double parallelisation!
 
An error in a #define prevented serial use with openpipeflow-1.10, which was a significant update to the double parallelisation!
Please update to openpipeflow-1.11 or later in this case.
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Please [[download]] openpipeflow-1.11 or later in this case.
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== I get error 'io_load_coll: Mp /= i_Mp' ==
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If you want to change the rotational symmetry use either [[changeMp.f90]] or [[change_Mp_alpha.f90]] utilities.  The former just changes the value in the file, the latter can be used to put e.g. 3 copies of an m=3 travelling wave in an m=1 domain.

Latest revision as of 06:31, 18 December 2017

How do I set up the libraries?

If you haven't already, please check out Getting_started#Libraries.

The necessity of some libraries appears to depend on distribution. Try commenting adding/commenting out -lcurl and/or -lblas

Where do I get initial conditions for a simulation?

The best initial condition is almost always to restart from a run with as similar parameters as possible. Some states may be found in the Database. If you have already run some jobs, remember that their parameters are recorded in main.info.

If such a state-file is not to hand, try utils/ic.f90. Artificial initial conditions tend to suffer far greater transients. Be prepared to use smaller timesteps and possible greater resolution to overcome the transient.

My job isn't starting properly, what's wrong?

If you started with a command like nohup ./main.out > OUT 2> OUT.err & , then check OUT.err and the head/tail of OUT first.

If you see an error from tim_check_cgce, it's likely that either an inappropriate initial condition was used, or that the resolution was inadequate.

Double-check all parameters were set correctly, see the main.info file. If you had a similar run that worked, check which parameters have changed: try e.g. diff main.info ../job005/main.info

How do I select resolution?

Best to start from a similar job and to check one of the spectrum files, e.g. vel_spec0010.dat. The values should fall by several orders, to approximately below 1e-5 in each dimension.

What is the spatial grid?

i_N radial points are non-equispaced, bunched near the walls, and very slightly near the axis to ensure spatial accuracy where fewer points are available for the banded matrices. The points are equispaced in theta on 3*i_M points and in z on 3*i_K points. The domain has radius 1 and length L=2*pi/d_alpha.

I get 'matrix inversion error 1'

An error in a #define prevented serial use with openpipeflow-1.10, which was a significant update to the double parallelisation! Please download openpipeflow-1.11 or later in this case.

I get error 'io_load_coll: Mp /= i_Mp'

If you want to change the rotational symmetry use either changeMp.f90 or change_Mp_alpha.f90 utilities. The former just changes the value in the file, the latter can be used to put e.g. 3 copies of an m=3 travelling wave in an m=1 domain.