I assume that you want to calculate it on many rows within the straight-table and this will take some time because each single row will need a separate calculation on the virtual table within the background: Logical Inference and Aggregations.
Personally I don't remember any special performance-issues with this kind of object and calculation but I remember other discussions about poor performance on it. One way to improve the performance could be to limit your table-rows by removing/replacing some very granular dimensions and/or conditions within the object/dimensions to display max. n number of rows.
A more general approach would be to look if there are possible optimizations within the datamodel - snowflake models or link-table approaches will have a lower gui-performance than a star-scheme or a big flat-table.
- Marcus
