[erlang-questions] Printed list to Erlang function

Hynek Vychodil <>
Wed Mar 30 20:12:20 CEST 2016


Every time I read a claim about how fast it will be I have urge test it. I
had an idea that constant map in a module could be faster than function
clause co I test it.

I was wrong and RAO is right as usual. Function using function clause seems
to be three times faster than using map.

x clause
+ map
+--------------------------------------------------------------------------+
|xxxxx                                                     +++++          +|
|xxxx                                                      ++++            |
|xxxx                                                      +++             |
|xxxx                                                       ++             |
|xxx                                                        ++             |
|xxx                                                        ++             |
|xx                                                         ++             |
|xx                                                         ++             |
|xx                                                         ++             |
|xx                                                         +              |
|xx                                                         +              |
|xx                                                         +              |
|xx                                                         +              |
|xx                                                         +              |
| x                                                         +              |
| x                                                         +              |
| x                                                         +              |
| x                                                         +              |
| x                                                         +              |
| x                                                         +              |
| x                                                         +              |
| x                                                         +              |
| x                                                         +              |
| x                                                         +              |
| x                                                         +              |
|                                                           +              |
|                                                           +              |
|                                                           +              |
|                                                           +              |
|                                                           +              |
|                                                           +              |
|                                                           +              |
|                                                           +              |
|                                                           +              |
||A|                                                                       |
|                                                         |_MA_|           |
+--------------------------------------------------------------------------+
Dataset: x N=50 CI=95.0000
Statistic     Value     [         Bias] (Bootstrapped LB‥UB)
Min:            3490.00
1st Qu.         3551.00
Median:         3591.00
3rd Qu.         3679.00
Max:            3945.00
Average:        3630.16 [     0.137534] (      3602.82 ‥       3664.56)
Std. Dev:       113.400 [     -1.81311] (      90.8425 ‥       141.539)

Outliers: 0/4 = 4 (μ=3630.30, σ=111.587)
        Outlier variance:      0.151802 (moderate)

------

Dataset: + N=50 CI=95.0000
Statistic     Value     [         Bias] (Bootstrapped LB‥UB)
Min:         1.09500e+4
1st Qu.      1.10160e+4
Median:      1.10400e+4
3rd Qu.      1.11270e+4
Max:         1.28270e+4
Average:     1.11055e+4 [     0.297998] (   1.10611e+4 ‥    1.12491e+4)
Std. Dev:       264.914 [     -31.0673] (      84.7956 ‥       582.629)

Outliers: 0/2 = 2 (μ=1.11058e+4, σ=233.847)
        Outlier variance:    9.45082e-2 (slight)

Difference at 95.0% confidence
        7475.36 ± 80.8533
        205.924% ± 2.22726%
        (Student's t, pooled s = 203.763)
------

It's about 31 million stopwords_clause:is_stopword/1 per second and 10
million stopwords_map:is_stopword/1 per second.

You can find code in gist
https://gist.github.com/pichi/2d10c93242d5057913d026a607f07dd4

Pichi

On Wed, Mar 30, 2016 at 4:05 AM, Lloyd R. Prentice <>
wrote:

> Wow! What a cool idea.
>
> Thanks, Richard.
>
> Best wishes,
>
> LRP
>
> Sent from my iPad
>
> > On Mar 29, 2016, at 8:47 PM, "Richard A. O'Keefe" <>
> wrote:
> >
> >
> >> On 30/03/16 5:59 am,  wrote:
> >> So, I have a printed list of stop words:
> >>
> >> http://www.ranks.nl/stopwords
> >>
> >> I'd like to turn this list into an Erlang function that I can query---
> >>
> >> stopwords() ->
> >>    ["word1", "word2" ... "wordN"].
> >>
> >> is_stopword(Word) ->
> >>    List = stopwords(),
> >>    lists_member(Word, List).
> > Even if there is some arcane reason why you want the collection of words
> > as a list, I strongly suggest generating
> >
> > is_stopword("a") -> true;
> > is_stopword("about") -> true;
> > ...
> > is_stopword("yourselves") -> true;
> > is_stopword(_) -> false.
> >
> > Open the list of stopwords in vi.
> > :1,$s/^.*$/is_stopword("&") -> true;/
> > :$a
> > is_stopword(_) -> false.
> > <ESC>
> >
> > The Erlang compiler will turn this into a trie, roughly speaking.
> > This will be *dizzyingly* faster than the code you outlined.
> >
> >
> >
> >
> >>
> >> All my efforts so far have evolved into ugly kludges. Seems to me there
> must be an elegant method that I'm overlooking.
> >>
> >> Some kind soul point the way?
> >>
> >> Many thanks,
> >>
> >> LRP
> >>
> >> *********************************************
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