Quad precision?

marupio · May 17, 2011, 14:17

How much trouble would it be to try implementing quad precision in OpenFOAM?

- Easy!
- Tough!
- Why would you want to try? The schemes are only "second order accurate", etc..

deepsterblue · May 17, 2011, 14:27

Are you referring to numerical precision, or something like fourth-order accuracy?

marupio · May 17, 2011, 14:49

Need more digits! I mean using "long double", or __float128.

deepsterblue · May 17, 2011, 14:54

I've implemented an arbitrary-precision data-type as a wrap-around to the GNU MPFR library. You should be able to use this as a drop-in replacement to the scalar class:

http://www.ecs.umass.edu/%7Esmenon/t...iPrecision.tgz

However, this is still emulation in software, so don't expect blazing performance.

marupio · May 17, 2011, 15:36

Thanks a lot, Sandeep!

I've downloaded it, and am in the process of figuring out how to use it. I'm guessing to use it in finiteVolume calculations, I need to define a new fvMatrix template specialization for a multiPrecisionScalar... fvMultiPrecisionScalar (basically identical to fvScalarMatrix).

Do you have any sample code that uses your multiPrecisionScalar class?

-Dave

May 17, 2011, 14:17	Quad precision?	#1
marupio Senior Member David Gaden Join Date: Apr 2009 Location: Winnipeg, Canada Posts: 437 Rep Power: 22	How much trouble would it be to try implementing quad precision in OpenFOAM? - Easy! - Tough! - Why would you want to try? The schemes are only "second order accurate", etc..

May 17, 2011, 14:27		#2
deepsterblue Senior Member Sandeep Menon Join Date: Mar 2009 Location: Amherst, MA Posts: 403 Rep Power: 25	Are you referring to numerical precision, or something like fourth-order accuracy? __________________ Sandeep Menon University of Massachusetts Amherst https://github.com/smenon

May 17, 2011, 14:54		#4
deepsterblue Senior Member Sandeep Menon Join Date: Mar 2009 Location: Amherst, MA Posts: 403 Rep Power: 25	I've implemented an arbitrary-precision data-type as a wrap-around to the GNU MPFR library. You should be able to use this as a drop-in replacement to the scalar class: http://www.ecs.umass.edu/%7Esmenon/t...iPrecision.tgz However, this is still emulation in software, so don't expect blazing performance. __________________ Sandeep Menon University of Massachusetts Amherst https://github.com/smenon

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May 17, 2011, 14:49		#3
marupio Senior Member David Gaden Join Date: Apr 2009 Location: Winnipeg, Canada Posts: 437 Rep Power: 22	Need more digits! I mean using "long double", or __float128.

May 17, 2011, 15:36		#5
marupio Senior Member David Gaden Join Date: Apr 2009 Location: Winnipeg, Canada Posts: 437 Rep Power: 22	Thanks a lot, Sandeep! I've downloaded it, and am in the process of figuring out how to use it. I'm guessing to use it in finiteVolume calculations, I need to define a new fvMatrix template specialization for a multiPrecisionScalar... fvMultiPrecisionScalar (basically identical to fvScalarMatrix). Do you have any sample code that uses your multiPrecisionScalar class? -Dave