Solver Precision in CFX5.
Hi people,
I know it sounds a weird question, but how do I know if I'm running in single or double precision in the CFX5? I've already searched the manual, but I found nothing it could help me. Where I can change it? In the Solver Manager? Build 5? Regards, cfd guy 
Re: Solver Precision in CFX5.
The problem is that no double recision version of the CFX5 solver has been released yet. There will be when CFX5.5 is released this fall.
What sort of problem are you doing that you need double precision? Certainly the coefficient matrix does not benifit much from double precision. Geometric calculations may be another story depending on the grid that you are using. Dan. 
Re: Solver Precision in CFX5.
(1). I had spent a lot of time trying to identify the source of error when using CFXTASCflow in 3D turbine applications some times ago. (2). I was convinced that the error was related to the single precision math used in the code. The doubleprecision version was not available then. My application required fine mesh and low Re turbulence model (twolayer model was available and was used). (3). This limited the Y+ values and the Reynolds number one can compute. (4). My feeling is: in the professional field, the doubleprecision math is required, for the solution to be possible or even useful. ( I had similar bad experience with an inhouse cfd code, which uses single precision math in I/O and each time the calculation do a restart read, it change the accuracy of the computed variables. To be in the CFD field, you must be a professional programmer and mathematician first. It is just a waste of time when you are creating garbages all the time.)

Re: Solver Precision in CFX5.
As you say, double precision math may be necessary, but it really only depends on the grid. With hexahedral meshes used in CFXTASCflow, when the elements have large aspect ratios then double precision may be necessary. It depends on the application. Double precision math only matters when accuracy to the 5th or 6th significant figure becomes important.
It is not clear that the coefficient matrix benefits from double precision as the coeffients all come from a linearisation of the various nonlinear terms anyways. And yes, you are correct, a double precision code should really restart in double precision. Dan. 
Re: Solver Precision in CFX5.
Thanks Dan,
Actually, I was just curious about it. Right now, I'm using hexa meshes and I didn't have any convergence problems yet. Regards, cfd guy 
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