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资源说明：Katz-Lazarsfeld vs Watts-Dodds
FunData Twitter Shootout -- OCaml ================================= This is the OCaml version of the [http://github.com/alexy/fundata1](Functional Data Shootout #1), implementing the Karmic Social Capital (KSC) on Twitter Communication Graph. The _fundata1_ repository contains all the necessary documentation about the shootout and data itself. Here we'll provide some implementation notes specific to [clams -- the OCaml implementation of fundata1](http://github.com/alexy/clams). Building -------- make The main executable is `sc.opt`, natively compiled. I tried to learn `omake` here, and it builds the executable, but that then fails to process command line arguments properly. I'm probably missing something. Running ------- You have to set `OCAMLRUNPARAM` or it will take forever. Smaller values may work: export OCAMLRUNPARAM='h=5G;s=1G' time ./sc.opt[maxDays] It reads the graph from _ _ and , which can be either `.json.hdb` or `.mlb` files. The latter ones are the results of `save_graph.opt`, reading in the former and saving in OCaml's own binary format via `Marshal.to_cahnnel`. The result is uncompressed. Data Preparation ---------------- If you want to create a smaller version of the original graphs, you can use the `save_graph` program. It's invoked as follows: ./save_graph.opt [N] [progress] If N is given, it will limit the number of entries read from the original -- only those will be used to build the OCaml graph and dump that into ` .mlb`. If progress is given, a dot will be printed after so many entries; the default is 10,000. Mostly Functional ----------------- This is a translation of [http://github.com/alexy/husky](husky), a Haskell implementation of KSC, into OCaml. At first, _husky_ was crashing under _ghc 6.12.1_ which had a GC bug. While Simon Marlow valiantly fought and quashed it, I translated _husky_ to _clams_. Some things stand out in OCaml, e.g. -- floating-point operators are distinct from integer ones, and contain a dot: `+. *. /.` -- Equality is tested with `=` or `==` -- but `== 0.` fails for `float`s. -- `safeDivide x y` doesn't check for `y = 0.`, but rather goes ahead with the division and then checks whether the result is `nan` or `infinite`. Just a Little Bit Imperative ---------------------------- OCaml's standard _map_ data structure is an imperative `Hashtbl`. At creation time, it wants to know how much to allocate; we just go ahead and allocate it all for the number of users, i.e. let orderN = 5000000 in Hashtbl.create orderN; Hence instead of folds, some operations are `List.iter`, and all those updating a `Hashtbl` have type `unit` and value `()`. This can present a moment's pause when translating back for a purely functional map. Better Maps ----------- Mauricio Fernandez and Mattias Giaovannini developed [http://eigenclass.org/R2/writings/finite-map-benchmarks](faster maps for OCaml). Some are functional, like `ternary`, some are imperative, like `Fasthashtbl`. The latter works best when there's no deletions, which is the case.
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