Hi Madhukar,
Did you check as to where the Query is taking more time,at what exact stage of Execution ?
For what period to period are you trying to exeute the report ?
Having you undertaken any performance tuning measures (Filters,Exclusions,Limit Period,etc)..which have been mentioned in SCN ?
For how many years of data do you have in your cube ?
Despite all this optimal measures...Still you are not able to cut down on the time then suggest you to go for APD , (Depending on your requirement).
rgds
SVU123