[ET Trac] [Einstein Toolkit] #1056: do not attempt reductions in local mode in SphericalSurface unless auto_res[n] is set

[Einstein Toolkit]

#1056: do not attempt reductions in local mode in SphericalSurface unless
auto_res[n] is set
-------------------+--------------------------------------------------------
 Reporter:  rhaas  |        Type:  defect               
   Status:  new    |    Priority:  minor                
Milestone:         |   Component:  EinsteinToolkit thorn
  Version:         |    Keywords:  SphericalSurface     
-------------------+--------------------------------------------------------
 currently SphericalSurface_SetupRes will attempt a reduction in local mode
 even if all auto_res values are false, ie if there are no spheres whose
 resolution is to be set automatically. This causes MPI hangs if different
 processors own different numbers of components, as produced by the
 recursive load balancer and
 carpet::same_number_of_components_on_each_process = false (true by default
 but might change).

 The attached patch ameliorates the situation by only attempting a
 reduction if auto_res[n] is set, thus at least allowing SphericalSurface
 to be used when all ntheta, nphi are giving explicitly. It also adds a
 comment warning about auto_res.

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/1056>
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