What does it mean when my program tells me: "fatal error: RTS exhausted max heap size (268435456 bytes)" ? My initial understanding was the GHC allocated (perhaps dynamically) a heap of unlimited size (at least so says +RTS -help) and when I run my (long memory grabbing) program without any RTS flags it gets about 1/4 of the way done (on my Windows box -- this is ghc5.03 the original snapshot) and then tells me this. So I go to increase the heap (i have 1g of ram) so I say "+RTS -H512m" and immediately it comes back to me with the same error (presumably in trying to allocate the heap?). I think there are really two error messages going on here: the first is truly that the heap is exhausted, but the second is more of "I can't allocate that much". Am I correct? If so, why not? I can run it with -H300m, but not -H350m (on the first RTS doesn't complain until later; on the second it complains immediately). How can I give my program more heap and why does -H300m give it more heap than without any RTS options which should give it unlimited heap? - Hal -- Hal Daume III "Computer science is no more about computers | hdaume@isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume