Hello, first let me remark that 6.8.1 is really remarkable, compiles faster and produces faster executables than 6.6.1. However, I have a problem with profiling, the time is always reported as 0.00 secs: Sun Nov 25 22:58 2007 Time and Allocation Profiling Report (Final) p28Master +RTS -P -hb -sstderr -RTS MMDataA total time = 0.00 secs (0 ticks @ 20 ms) total alloc = 1,313,421,840 bytes (excludes profiling overheads) although it took more than 15 seconds: INIT time 0.00s ( 0.00s elapsed) MUT time 16.10s ( 16.41s elapsed) GC time 10.76s ( 11.16s elapsed) RP time 0.00s ( 0.00s elapsed) PROF time 0.00s ( 0.00s elapsed) EXIT time 0.00s ( 0.00s elapsed) Total time 26.86s ( 27.57s elapsed) Could that be caused by commenting out the lines ifeq "$(GhcThreaded)" "YES" SRC_HC_OPTS += -threaded endif in compiler/Makefile.ghcbin ? I did that because if I build ghc with -threaded, the times reported with :set +s in ghci are rubbish (I have a linux 2.4.20 kernel, and the threads don't support process-wide times; and no, I'm not likely to upgrade, SuSE 8.2 is the only OS that ever worked properly for me). If that's the cause, too bad, I'll have to revert to 6.4.2 for profiling :( In 6.6.1, -O2 and -prof -auto-all don't work together well, I have a programme where that combination of options results in an instant wrong output, while the combinations -prof -auto-all -O1 -prof -auto-all -O2 -prof lead to the correct output calculated in 10 to 13 seconds. If you're interested in that bug, I could send you the code, it's short enough. Thanks, Daniel