RANX for Delay in Project

[soni27]

 I need to RANK based on the Delay in Days in the project scehdule.

I am using gthe following  Measure;

Delay Ranking try1:=IF(NOT(ISBLANK([Delay in Days])), RANKX (ALLSELECTED(fScheduleInputDataAll),  [Delay in Days]), BLANK())

The Issue is :

It is very very slow.

The Results are not as expected