Of course, I don't mean to suggest that we shouldn't worry about the software code. ADIRUs have a failure rate of the order between 1/1000 and 1/10000. We still need triple redundancy to avoid a catastrophe. We need to ensure that independent computer software errors do not go uncorrected, whether caused by an ADIRU failure or be a cosmic ray upsetting a single bit.
In general, we've done a pretty good job of not have the software make mistakes in calculations. Where we may have fallen short is in writing our requirements to take these ADIRU failures or other single events into account. I was distressed during my previous employment when my boss reacted to the QANTAS upset with "Well, it was only an ADIRU failure<"when the response should have been "How could an ADURU failure make its way through to the flight control surfaces.
Dick