Try this...
@Grapes(
@Grab(group='org.apache.commons', module='commons-math3',
version='3.6.1')
)
import org.apache.commons.math3.random.MersenneTwister
import groovy.time.*
def benchmark = { closure ->
def start = new Date()
closure.call()
TimeCategory.minus(new Date(), start)
}
def rng = new MersenneTwister()
def roll = {
rng.nextInt(6) + rng.nextInt(6) + rng.nextInt(6) + 3
}
int N = 1000000
def results = [:].withDefault{0}
def time = benchmark {
(1..N).each {
int n = roll()
results[n]++
}
}
println time
results.each { key, value -> println "$key: $value" }
when I run it i get this output
0.565 seconds
12: 115149
14: 69665
18: 4546
6: 46159
10: 125497
11: 125188
9: 116157
8: 97236
15: 46510
7: 69281
13: 96961
5: 27663
16: 27731
3: 4572
17: 13827
4: 13858
Erick Nelson
Senior Developer
HD Supply, FM
Cell 858-740-6523
Home 760-930-0461
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On 3/28/17, 1:25 PM, "Paul Moore" <p.f.mo...@gmail.com> wrote:
>I'm very much a newbie with Groovy, so I apologise in advance if this
>is not the right place for questions like this. I couldn't find
>anywhere else that looked like a better option - if there is somewhere
>I should have asked, feel free to redirect me.
>
>I want to write a simulation script using Groovy - this is something
>of a hobby challenge for me, I have a friend who has done a similar
>task in C++, and I'm looking for a more user-friendly language to
>write the code, while not losing too much performance over the C
>version.
>
>The code is basically to simulate "a game". The particular game is
>defined by the user, as a function that generates scores. The program
>runs the game many times, and summarises the distribution of the
>results. Basically, a Monte Carlo simulation. My current code in
>Groovy for this, using "roll 3 dice and add up the results" as the
>target game, looks as follows:
>
>@Grapes(
> @Grab(group='org.apache.commons', module='commons-math3',
>version='3.6.1')
>)
>import org.apache.commons.math3.random.MersenneTwister
>
>def benchmark = { closure ->
> start = System.currentTimeMillis()
> closure.call()
> now = System.currentTimeMillis()
> now - start
>}
>
>rng = new MersenneTwister()
>
>int roll() {
> rng.nextInt(6) + rng.nextInt(6) + rng.nextInt(6) + 3
>}
>
>int N = 1000000
>def results = [:]
>
>def time = benchmark {
> N.times {
> int n = roll()
> results[n] = results.containsKey(n) ? results[n] + 1 : 1
> }
>}
>
>println "Took ${time/100} sec"
>for (e in results.sort()) {
> println "$e.key: $e.value"
>}
>
>This does exactly what I want, but takes about 5 seconds to run the
>simulation on my PC. My friend's C++ code runs a similar simulation in
>about 0.1 second. That's a massive penalty for Groovy, and likely
>means that for more realistic simulations (which would be a lot more
>complex than 3d6!) I wouldn't even be close to competitive.
>
>The code above is completely unoptimised. I know that Groovy's dynamic
>programming features can introduce some overhead, but I also get the
>impression from the documentation that by careful use of exact types,
>and similar techniques, this can be speeded up a lot (the docs claim
>potentially better than C performance in some cases).
>
>What should I be looking at to optimise the above code? The areas I
>can think of are:
>
>1. The RNG. I assume that the apache commons code is pretty efficient,
>though. I do want a reasonably decent RNG, and I'd heard that the JVM
>RNG is not sufficient for simulation. For now I'm assuming that this
>is sufficiently good.
>2. The roll() function. This is the core of the inner loop, and likely
>the big bottleneck. I've declared the type, which I guess is the first
>step, but I don't know what else I can do here. I tried a
>CompileStatic annotation, but that gave me errors about referencing
>the rng variable. I'm not sure what that implies - is my code doing
>something wrong in how it references the global rng variable?
>3. Collecting the results in a map is likely not ideal. Is there a
>better data structure I should be using? I basically want to be able
>to count how many times each result appears - results will be integers
>(in certain cases I might want non-integers but I can handle them
>exceptionally) but I don't necessarily know the range in advance (so
>I'd avoid a static array unless it gives significant performance
>benefits - when I did a quick test, I got about a second faster
>runtime, noticeable, but not enough to get me anywhere near my sub-1
>second target)
>
>I tried using the GProf profiler to see if that shed any light on what
>I should do. When I ran with a realistic number of iterations it took
>forever and then failed with an out of memory error. Dropping it to
>10000 iterations, I got
>
> % cumulative self self total self total
>self total
>time seconds seconds calls ms/call ms/call min ms min ms
>max ms max ms name
>34.5 0.04 0.04 10000 0.00 0.00 0.00 0.00
>0.91 1.13 blackpool$_run_closure2$_closure3.roll
>18.5 0.06 0.02 39984 0.00 0.00 0.00 0.00
>0.53 0.53 java.lang.Integer.plus
>15.9 0.08 0.02 10000 0.00 0.01 0.00 0.00
>0.28 1.26 blackpool$_run_closure2$_closure3.doCall
>11.0 0.10 0.01 30000 0.00 0.00 0.00 0.00
>0.36 0.36 org.apache.commons.math3.random.MersenneTwister.nextInt
> 5.1 0.10 0.00 10000 0.00 0.00 0.00 0.00
>0.19 0.19 java.util.LinkedHashMap.containsKey
> 4.4 0.11 0.00 10000 0.00 0.00 0.00 0.00
>0.02 0.02 java.util.LinkedHashMap.putAt
> 4.0 0.12 0.00 1 5.25 125.62 5.25 125.62
>5.25 125.62 java.lang.Integer.times
> 3.9 0.12 0.00 9984 0.00 0.00 0.00 0.00
>0.02 0.02 java.util.LinkedHashMap.getAt
> 2.2 0.12 0.00 1 2.85 128.48 2.85 128.48
>2.85 128.48 blackpool$_run_closure2.doCall
>
>But I don't really know how to interpret that. (Also, am I somehow
>using GProf wrongly? It seems like it shouldn't run out of memory
>profiling a 5-second program run...)
>
>Can anyone offer any advice on what I should be looking at here?
>
>Thanks,
>Paul
