UDF should be written in C or C++ standard?

Roh · September 1, 2018, 15:36

Guys,
UDF should be written in C or C++ standard? in some places I've heared that it should be written in C and another places heared that should be written in C++? if C++, so can we use OOP?

blackmask · September 2, 2018, 00:30

It does not matter if you use compiled UDF. You can do a major part of your work using C/C++/FORTRAN as you please. However you need to wrap it with a C interface. You should stick to C if mixed language programming sounds foreign to you.

pakk · September 3, 2018, 05:41

The simple answer: C.
Everything in the manual is written in C. All examples that you will encounter: C.

Now, it is possible to set C up such that it accepts functions from Fortran or C++. For 99.999% of all cases, this is needlessly complicated, and should not be done. Just do it in C.

gearboy · September 10, 2018, 02:26

Quote:

Originally Posted by Roh

Guys,
UDF should be written in C or C++ standard? in some places I've heared that it should be written in C and another places heared that should be written in C++? if C++, so can we use OOP?

See the UDF debugging tool using VC++.
It writes udf in C++ language, so OOP is of course allowed.

https://vcudfstudio.bitbucket.io/

elochana · December 30, 2020, 08:13

Ansys Fluent UDF manual 2019 R2 says
"A user-defined function, or UDF, is a C or C++ function that can be dynamically loaded with the ANSYS Fluent solver to enhance its standard features. For example, you can use a UDF to:..."

pakk · December 30, 2020, 09:14

Interesting find.
As far as I am aware, Fluent compiles with the c-compiler. C and C++ are not the same, but share syntax, so many C++ functions are also valid C. But not all.

So, unless there is an option that I am not aware of to change the compiler, this is just marketing. They can claim to support a popular language, and they are misleading, but just enough correct to defend it.

My advice remains: use C.
(Exception for experienced C++ programmers, but they wouldn't ask this question.)

elochana · December 31, 2020, 09:09

I will try a simple C++ udf both as interpreted and compiled and see..

pakk · December 31, 2020, 11:36

Nice idea, can you share the results? (and the simple C++ udf?)

September 1, 2018, 15:36	UDF should be written in C or C++ standard?	#1
Roh Senior Member Join Date: Sep 2017 Posts: 130 Rep Power: 9	Guys, UDF should be written in C or C++ standard? in some places I've heared that it should be written in C and another places heared that should be written in C++? if C++, so can we use OOP?

September 2, 2018, 00:30		#2
blackmask Senior Member Join Date: Aug 2011 Posts: 421 Blog Entries: 1 Rep Power: 22	It does not matter if you use compiled UDF. You can do a major part of your work using C/C++/FORTRAN as you please. However you need to wrap it with a C interface. You should stick to C if mixed language programming sounds foreign to you. Roh and THA SEANGHAI like this.

September 3, 2018, 05:41		#3
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 27	The simple answer: C. Everything in the manual is written in C. All examples that you will encounter: C. Now, it is possible to set C up such that it accepts functions from Fortran or C++. For 99.999% of all cases, this is needlessly complicated, and should not be done. Just do it in C. Roh likes this.

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December 30, 2020, 08:13		#5
elochana New Member Join Date: Jun 2011 Posts: 11 Rep Power: 15	Ansys Fluent UDF manual 2019 R2 says "A user-defined function, or UDF, is a C or C++ function that can be dynamically loaded with the ANSYS Fluent solver to enhance its standard features. For example, you can use a UDF to:..."

December 30, 2020, 09:14		#6
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 27	Interesting find. As far as I am aware, Fluent compiles with the c-compiler. C and C++ are not the same, but share syntax, so many C++ functions are also valid C. But not all. So, unless there is an option that I am not aware of to change the compiler, this is just marketing. They can claim to support a popular language, and they are misleading, but just enough correct to defend it. My advice remains: use C. (Exception for experienced C++ programmers, but they wouldn't ask this question.)

December 31, 2020, 09:09		#7
elochana New Member Join Date: Jun 2011 Posts: 11 Rep Power: 15	I will try a simple C++ udf both as interpreted and compiled and see..

December 31, 2020, 11:36		#8
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 27	Nice idea, can you share the results? (and the simple C++ udf?)