You may well be right. As far as I can recall, though, as of the last time I was regularly using Prolog, trying to do serious work on a (say) 1000x1000 array w

You may well be right. As far as I can recall, though, as of the last time I was regularly using Prolog, trying to do serious work on a (say) 1000x1000 array was a recipe for disaster. The exception would be Turbo Prolog, but it was a rather restrictive subset of the language. Fast as hell, though.