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Constant eps

Posted 2015/08/12 12:08 JST Fluid & Heat, Computational Fluid Dynamics (CFD) 2 Replies

eMonsulee
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Greetings,

What does constant eps do when it is added to the source term (f) of a PDE? Does it help convergence?

Thanks.

Eric

2 Replies Last Post 2015/08/13 2:57 JST
Lasse Murtomäki
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Posted: 10 years ago 2015/08/12 16:18 JST
eps is sometimes needed to prevent error messages if a variable is raised to a non-integer power (like square root). As far as I know it does not do anything else.
eps is sometimes needed to prevent error messages if a variable is raised to a non-integer power (like square root). As far as I know it does not do anything else.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 10 years ago 2015/08/13 2:57 JST
Hi

"eps" is the smallest real number that added to "1.0" can be distinguished from "1.0" by the binary representation of a floating point real numbers.

It's a "clean" programming trick to avoid divisions by "0" mostly ... and is required only because the binary representation of Real number is very sparse and is limited in absolute and relative precision
--
Good luck
Ivar
Hi "eps" is the smallest real number that added to "1.0" can be distinguished from "1.0" by the binary representation of a floating point real numbers. It's a "clean" programming trick to avoid divisions by "0" mostly ... and is required only because the binary representation of Real number is very sparse and is limited in absolute and relative precision -- Good luck Ivar

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