LINEQN_solver_ScalarSystems

Default: LINEQN_solver_ScalarSystems = 'BCN2'

option	description
'BiCG' and 'BCG1'	BiCGstab, using matrix-times-vector emulation for the big system (i.e. do not construct the linear system explicitly, but provide a subroutine that computes the result of the matrix-vector-operation)
'BCG2'	BiCGstab(2), using matrix-times-vector-emulation
'SAMG'	SAMG-solver, Fraunhofer SCAI
'BCN1'	BiCGstab, no SPAI-preconditioning
'BCN2'	BiCGstab(2), no SPAI-preconditioning, default

Advanced Usage:

• Auto-chooser This option allows the choice between two solvers xxxx and yyyy from the list above every n time steps. Syntax:
  LINEQN_solver_ScalarSystems = 'AUTO:xxxx:yyyy:_nn_:_mm_'
• Choice of solvers It is possible to select different solvers for solving Pressure, Temperature, and CODI, including auto choosing for each quantity separately. Syntax:
  LINEQN_solver_ScalarSystems = 'p:xxxx T:yyyy CODI:zzzz TURB:pppp' LINEQN_solver_ScalarSystems = 'xxxx p:yyyy' LINEQN_solver_ScalarSystems = 'AUTO:xxxx:yyyy:_n1_ p:AUTO:uuuu:vvvv:_n2_:_m2_ T:AUTO:aaaa:bbbb:_n3_ CODI:rrrr:ssss:_n4_ TURB:pppp:qqqq:_n5_'
  • p: -> solvers for all pressure items
  • T: -> solver for temperature
  • CODI: -> solver for all CODI items
  • TURB: -> solver for all items of turbulence modelling
• Remarks:
  • The numbers _nn_, _n1_ etc. denote the number of time steps after which both solvers are checked for their performance concerning the currect linear system. For the next period, if _nn_, _n1_ etc. are non-negative, the fastest solver is chosen. If _nn_, _n1_ etc. are negative, the comparison is carried out only at the prescribed |_nn_|, |_n1_| time steps.
  • The numbers _mm_, _m1_ etc. denote how many time steps the currently selected solver is allowed to fail before the test is performed again.
  • The numbers _nn_, _n1_, _mm_ etc. have to be 4-digit-characters, including sign .
  • It is possible to have a default choice, and a quantity specific override choice, but the default choice must come *FIRST*!

Example: If the Output Level >=3, the user is informed about the timings as well as the decisions of the automatic solver control. More information: BiCGstab, BiCGstab(2), SAMG