zero divide

D.ko · April 13, 2013, 06:01

in UDF
i code like below

RET(ILOC,1)=d*DEXP(exvar)
and exvar = c/kb (d is very small value)
kb is boltzman constant so it has very small value and c is constant
when i apply this UDF in cfx, solver shows error message that Zero divide . But it is not zero.
i annouced exvar and kb as double precision

when i made
RET(ILOC,1)=DSQRT(exvar)
it also shows same error, so i changed
exvar = kb/c
RET(ILOC,1)=1/DSQRT(exvar)
and it works.
but DEXP is not the case. i cannot change that
how can i get result?

JuPa · April 15, 2013, 05:08

Sounds like rounding error. Try double precision and your problem may go away.

HOWEVER read about what double precision is, and what it means when you switch it on.

April 13, 2013, 06:01	zero divide	#1
D.ko New Member DongGunKo Join Date: Apr 2013 Posts: 13 Rep Power: 13	in UDF i code like below RET(ILOC,1)=d*DEXP(exvar) and exvar = c/kb (d is very small value) kb is boltzman constant so it has very small value and c is constant when i apply this UDF in cfx, solver shows error message that Zero divide . But it is not zero. i annouced exvar and kb as double precision when i made RET(ILOC,1)=DSQRT(exvar) it also shows same error, so i changed exvar = kb/c RET(ILOC,1)=1/DSQRT(exvar) and it works. but DEXP is not the case. i cannot change that how can i get result?

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April 15, 2013, 05:08		#2
JuPa Senior Member Mr CFD Join Date: Jun 2012 Location: Britain Posts: 361 Rep Power: 14	Sounds like rounding error. Try double precision and your problem may go away. HOWEVER read about what double precision is, and what it means when you switch it on.