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Work on improving efficiency of mapping over arrays.

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This commit is contained in:
Simon Brooke 2014-10-18 15:50:31 +01:00
parent cd6b4ae10c
commit f06febd7c6
3 changed files with 20 additions and 17 deletions
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3
project.clj
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@ -11,8 +11,7 @@
:jvm-opts ["-Xmx4g"] :jvm-opts ["-Xmx4g"]
:license {:name "GNU General Public License v2" :license {:name "GNU General Public License v2"
:url "http://www.gnu.org/licenses/gpl-2.0.html"} :url "http://www.gnu.org/licenses/gpl-2.0.html"}
:plugins [[lein-marginalia "0.7.1"] :plugins [[lein-marginalia "0.7.1"]]
[lein-gorilla "0.3.2"]]
:dependencies [[org.clojure/clojure "1.5.1"] :dependencies [[org.clojure/clojure "1.5.1"]
[org.clojure/math.combinatorics "0.0.7"] [org.clojure/math.combinatorics "0.0.7"]
[org.clojure/tools.trace "0.7.8"] [org.clojure/tools.trace "0.7.8"]

7
src/mw_engine/drainage.clj
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@ -28,12 +28,13 @@
:altitude :altitude
(or (:altitude cell) 0) >))))) (or (:altitude cell) 0) >)))))
(defn flow (def flow
"Compute the total flow upstream of this `cell` in this `world`, and return a cell identical "Compute the total flow upstream of this `cell` in this `world`, and return a cell identical
to this one but having a value of its flow property set from that computation. to this one but having a value of its flow property set from that computation.
Flow comes from a higher cell to a lower only if the lower is the lowest neighbour of the higher." Flow comes from a higher cell to a lower only if the lower is the lowest neighbour of the higher."
[world cell] (memoize
(fn [world cell]
(cond (cond
(not (nil? (:flow cell))) cell (not (nil? (:flow cell))) cell
(<= (or (:altitude cell) 0) *sealevel*) cell (<= (or (:altitude cell) 0) *sealevel*) cell
@ -42,7 +43,7 @@
{:flow (+ (:rainfall cell) {:flow (+ (:rainfall cell)
(apply + (apply +
(map (fn [neighbour] (:flow (flow world neighbour))) (map (fn [neighbour] (:flow (flow world neighbour)))
(flow-contributors world cell))))}))) (flow-contributors world cell))))})))))
(defn flow-world (defn flow-world
"Return a world like this `world`, but with cells tagged with the amount of "Return a world like this `world`, but with cells tagged with the amount of

11
src/mw_engine/utils.clj
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@ -2,7 +2,7 @@
(ns mw-engine.utils (ns mw-engine.utils
(:require (:require
[clojure.core.reducers :as r] ;; [clojure.core.reducers :as r]
[clojure.math.combinatorics :as combo])) [clojure.math.combinatorics :as combo]))
(defn abs (defn abs
@ -32,13 +32,16 @@
(defn map-world (defn map-world
"Apply this `function` to each cell in this `world` to produce a new world. "Apply this `function` to each cell in this `world` to produce a new world.
the arguments to the function will be the world, the cell, and any the arguments to the function will be the world, the cell, and any
`additional-args` supplied" `additional-args` supplied. Note that we parallel map over rows but
just map over cells within a row. That's because it isn't worth starting
a new thread for each cell, but there may be efficiency gains in
running rows in parallel."
([world function] ([world function]
(map-world world function nil)) (map-world world function nil))
([world function additional-args] ([world function additional-args]
(into [] (into []
(r/map (fn [row] (pmap (fn [row]
(into [] (r/map (into [] (map
#(apply function #(apply function
(cons world (cons % additional-args))) (cons world (cons % additional-args)))
row))) row)))