#13070: time after evaluation -------------------------------------+------------------------------------- Reporter: vanto | Owner: Type: feature request | Status: closed Priority: normal | Milestone: 8.0.2 Component: GHCi | Version: 8.0.1 Resolution: invalid | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by rwbarton): * status: new => closed * resolution: => invalid Comment: If you can figure out how to run ghci on a processor from 1974 then you might get consistent runtimes from ghci. With a modern preemptive- multitasking OS using virtual memory and running on a pipelining, branch- predicting processor with many levels of caching, where a memory read might cost 4 to 200 cycles depending what level of the cache it is in (or orders of magnitude more if it's swapped out to disk!), you cannot add up cycle counts like this any more. Unfortunately it does mean that there is a significant, effectively random component of program runtime; that's the cost of computers getting many thousands of times faster. Even your processor's clock rate is not constant any more. It's increased and decreased according to demand to save power when the processor is idle, or to avoid overheating. The numbers displayed by `:set +s` are the real times, and they are not fixed because the real times are not fixed. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13070#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler