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Excel 2010: Asynch XLL UDFs

September 8, 2009 Leave a comment Go to comments

The Excel team blogged about async xll udfs today.

There is one other unique investment in the area of calculation that I want to briefly mention:Asynchronous XLL User-Defined Functions (Asynch XLL UDFs). The idea behind Asynch XLL UDFs is this: we know that some of our customers use XLL UDFs as a way to fetch data from external data servers. The CPU usage on the machine running Excel isn’t very heavy, but the server handling the request may take a while to return the requested data. If you have 100 of these functions in A1:A100 for example, you can be waiting quite a while for your workbook to calculate, because Excel processes those cells one at a time. Since the local machine isn’t doing any heavy CPU processing, with Excel 2010 we’ve enabled the functionality to send all 100 XLL UDFs calls at one time, allowing the backend servers to process the requests in parallel.

IMO, this is a much-needed feature. In the past, you’d have to write an Excel RTD server to fetch the values asynchronously, even if the backend was returning static data (or an addin wrapping the RTD server).  This lead to PnL & Risk workbooks containing formulae written by both the users and the development team; not an ideal support scenario. The async udfs should help reduce user dependence on the IT team as far as maintenance of the formulae is concerned.

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