TM1 Forum

Posted: **Fri Oct 19, 2018 2:21 pm**

Hi,

Am looking at making a TM1 model (which calculates housing rents) a little more efficient, just looking at the rules it raised my curiosity which is the best way to write a rule,

Option 1

Code: Select all

['Formula Rent Calc A']=N:

if(NUMBR(SUBST(!Year,1,4)) > NUMBR(SUBST(!UH_Versions,1,4)),

DB('UH_Current_Year_Account_Values',!Year,!UH_Versions,!UH_House_Acc,!UH_Debit_Type,'Bed Weighting') *

DB('UH_Debit_Code_Assumptions',!Year,!UH_Versions,!UH_Debit_Type,'National Average Rent') *

DB('UH_Debit_Code_Assumptions',!Year,!UH_Versions,!UH_Debit_Type,'Relative County Manual Earnings'),STET);

Option 2

Code: Select all

['Formula Rent Calc A']=N:


DB(if(NUMBR(SUBST(!Year,1,4)) > NUMBR(SUBST(!UH_Versions,1,4)),'UH_Current_Year_Account_Values', Stet), !Year,!UH_Versions,!UH_House_Acc,!UH_Debit_Type,'Bed Weighting')

*

DB(if(NUMBR(SUBST(!Year,1,4)) > NUMBR(SUBST(!UH_Versions,1,4)),'UH_Debit_Code_Assumptions', Stet), !Year,!UH_Versions,!UH_Debit_Type,'National Average Rent')

*

DB(if(NUMBR(SUBST(!Year,1,4)) > NUMBR(SUBST(!UH_Versions,1,4)),'UH_Debit_Code_Assumptions', Stet), !Year,!UH_Versions,!UH_Debit_Type,'Relative County Manual Earnings');

The rule is currently as per option 1 but was thinking of changing it to option 2, I doubt it will make little difference but am interested what might be considered best practice

cheers, Mark

Posted: **Fri Oct 19, 2018 2:30 pm**

No, go for option 1. Option 2 makes very little sense actually.

Posted: **Fri Oct 19, 2018 2:31 pm**

Ok thanks Wim

Posted: **Fri Oct 19, 2018 2:51 pm**

This goes for most languages (mostly c based, but will apply here as well), try to avoid extra conditionals when possible. Depending on the case, this is sometimes unavoidable, but in your situation the extra calls in option 2 would be considered more "expensive" than the first (i.e. more "cycles" to check unnecessary conditions). Now, this isn't a resource constrained instance where we are trying to squeeze the most out of scarce memory, so always default to readability. Option 1 is much cleaner, and the guy who comes after you will greatly appreciate only having to read that conditional check once.

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