Shivkumar Chandrasekaran wrote: > I have a gc efficiency problem for which I require some advice. I have > read both the O'Reilly book and the manual on gc. > > I am implementing a fast direct matrix solver for 2D PDEs. So it uses > the Bigarray module a lot. I have two versions of my algorithm. On is an > in-core algorithm and the other is the same solver, except that it is > out-of-core (most of the matrices are stored in disk files). > Unfortunately the out-of-core solver is *faster* than the in-core > solver for the identical problem! I was expecting the out-of-core solver > to be 10 times slower. If your in-core version is swapping, your out-core is faster because you optimize yourself the disk access compared to the swapping which knows nothing about your data and algorithm. Moreover, at GC time all the matrices/vectors need to be accessed and this produces more swapping ... I am concluding that gc is to blame. Below I give > the gc stats just before and after the solver routine is called in the > in-core solver: > > "Just before" "Just after" > minor_words: 46243376 139259767 > promoted_words: 928267 2595523 > major_words: 2883087 39489766 > minor_collections: 1412 4591 > major_collections: 18 52 > heap_words: 2150400 1044480 > heap_chunks: 35 17 > top_heap_words: 2150400 5038080 > live_words: 1842373 840037 > live_blocks: 253926 116816 > free_words: 307180 204440 > free_blocks: 47368 17 > largest_free: 10928 61440 > fragments: 847 3 > compactions: 0 2 > > I tried changing some parameters using Gc.set but it did not make a > significant difference. Does anybody see any obvious gc problems from > the above data? Thanks, > > --shiv-- > > > PS: I wrote the out-of-core solver in just 3 days once the in-core > solver was done, all in O'Caml. This would have have taken much longer > in Fortran/C. Thanks to the O'Caml team. > > ------------------- > To unsubscribe, mail caml-list-request@inria.fr Archives: > http://caml.inria.fr > Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: > http://caml.inria.fr/FAQ/ > Beginner's list: http://groups.yahoo.com/group/ocaml_beginners -- Christophe Raffalli Université de Savoie Batiment Le Chablais, bureau 21 73376 Le Bourget-du-Lac Cedex tél: (33) 4 79 75 81 03 fax: (33) 4 79 75 87 42 mail: Christophe.Raffalli@univ-savoie.fr www: http://www.lama.univ-savoie.fr/~RAFFALLI --------------------------------------------- IMPORTANT: this mail is signed using PGP/MIME At least Enigmail/Mozilla, mutt or evolution can check this signature ---------------------------------------------