The profiling report from my program compiled with GHC 6.0 with -O -fvia-C on Mac OS X isn't making a lot of sense. The line with the most time, 30.1%, has an entry count of zero, as do most of them: exprLetMap Org.Org.Semantic.HScheme.Interpret.LambdaExpression 1939 0 0.3 0.0 30.3 0.0 liftF2 Org.Org.Semantic.HBase.Category.Functor 1940 0 0.0 0.0 30.1 0.0 liftF1 Org.Org.Semantic.HBase.Category.Functor 1941 0 30.1 0.0 30.1 0.0 It's also a fairly unlikely candidate for time consumption. liftF1 is defined as simply equal to fmap, which presumably doesn't have a cost-centre because it's defined in the standard libraries. But the instance of fmap that it calls is fairly trivial. Am I misinterpreting the report, or would I be better off profiling a unoptimised program to see where the slow bits are in that? I have successfully improved code based on reports from unoptimised programs from GHC 5.*, since those reports made much more sense. -- Ashley Yakeley, Seattle WA