Regarding slow computation

hemmt · February 14, 2017, 09:07

Hello every one,
I m simulating atmospheric flow around buildings using LES. for this I have created an UDF as attached for fluctuating velocity profile.
but using this UDF, computation is getting very slow.
as I m quite new user to UDF.
so please guide to improve this situation regarding slow computaion.

kirmaks · February 21, 2017, 03:27

Hallo,

you have two loops in the code and You are performing many "pow" operations. You can try to save some time putting some repeating math into separate variables, i.e. replace y/y0 with y_prime, where y_prime=y/y0 is computed only once in the begining of the loop. The same is for the parameters B1, B2 and B3 where You can put 70.8/U/U into one variable.

You are also using 500 iterations for the inside loop. You may consider to reduce this number to a reasonable value if You want to increase the performance.

Also You may compile the UDF (I don't know is it interpreted or compiled).

Best regards, Maksim

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February 21, 2017, 03:27		#2
kirmaks Member KirMaks Join Date: Aug 2016 Posts: 34 Rep Power: 9	Hallo, you have two loops in the code and You are performing many "pow" operations. You can try to save some time putting some repeating math into separate variables, i.e. replace y/y0 with y_prime, where y_prime=y/y0 is computed only once in the begining of the loop. The same is for the parameters B1, B2 and B3 where You can put 70.8/U/U into one variable. You are also using 500 iterations for the inside loop. You may consider to reduce this number to a reasonable value if You want to increase the performance. Also You may compile the UDF (I don't know is it interpreted or compiled). Best regards, Maksim