On Sat, Feb 09, 2013 at 09:56:12AM +0100, Johan Holmquist wrote: > As a software developer, who typically inherits code to work on rather > than simply writing new, I see a potential of aggressive compiler > optimizations causing trouble. It goes like this: > > Programmer P inherits some application/system to improve upon. Someday > he spots some piece of rather badly written code. So he sets out and > rewrites that piece, happy with the improvement it brings to clarity > and likely also to efficiency. > > The code goes into production and, disaster. The new "improved" > version runs 3 times slower than the old, making it practically > unusable. The new version has to be rolled back with loss of uptime > and functionality and management is not happy with P. > > It just so happened that the old code triggered some aggressive > optimization unbeknownst to everyone, **including the original > developer**, while the new code did not. (This optimization maybe even > was triggered only on a certain version of the compiler, the one that > happened to be in use at the time.) > > I fear being P some day. > > Maybe this is something that would never happen in practice, but how > to be sure...
An interesting point, but I think here "P" is still at fault. If we're talking about important software, there will be regression tests, both in terms of quality and performance? Surely there will be a canary period, parallel running of the old and new system, etc.? regards, iustin _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
