For me slow J is fast enough, but I really was delighted when this worked
at all. No doubt it is slow.
]A=:?10$100
63 92 51 92 39 15 43 89 36 69
f=:/:
g=:/: { ]
h=:f;g
h A
--------------------T-----------------------------┐
│5 8 4 6 2 0 9 7 1 3│15 36 39 43 51 63 69 89 92 92│
L-------------------+------------------------------
Linda
-----Original Message-----
From: programming-boun...@forums.jsoftware.com
[mailto:programming-boun...@forums.jsoftware.com] On Behalf Of Roger Hui
Sent: Wednesday, March 05, 2014 8:45 PM
To: Programming forum
Subject: Re: [Jprogramming] a good bar bet!
It's necessary to have the g because I asked for both the sort (s) and the
grade, which would be the g.
The problem arose in an application where the sort and the grade are used
for something else.
On Wed, Mar 5, 2014 at 4:32 PM, Don Kelly <d...@shaw.ca> wrote:
> Why is it necessary to have 'g'
>
> repeating the process on my machine which is obviously slower gives an
> insignifcant time difference.
>
> 20 timer 's=:/:~x [ /:x'
>
> 0.172937
>
>
> 20 timer 's=:/:~x [ g=:/:x'
>
> 0.173672
>
> Is it because storage is necessary and it is just as fast to store to a
> named location rather than to some temporary storage?
> Space differences seem small.
>
> Don Kelly
>
>
> On 05/03/2014 12:11 PM, Joe Bogner wrote:
>
>> Yes, the grade is done regardless. Here's my reasoning: In the
>> incumbent version, s is taken from the grade with from { which is
>> slower than just resorting.
>> It seems like the difference between sorting and selecting by indexes.
>> I am surprised if that's the answer though because selecting by index
>> should be fast since it's a contiguous array.
>>
>> jtifrom looks more complicated than jtsortc but I haven't been able to
>> figure out how jtsortc works.
>>
>> On Wed, Mar 5, 2014 at 2:50 PM, Roger Hui <rogerhui.can...@gmail.com>
>> wrote:
>>
>>> x=: a.{~ 1e7 ?@$ 256
>>> timer=: 6!:2
>>>
>>> 10 timer 's=:x{~g=:/:x'
>>> 0.136961
>>> 10 timer 's=:/:~x [ g=:/:x'
>>> 0.0765459
>>>
>>> 10 timer '/:~x'
>>> 0.012887
>>> 10 timer 'x{~g'
>>> 0.065751
>>> 10 timer '/:x'
>>> 0.0606987
>>>
>>>
>>>
>>> On Wed, Mar 5, 2014 at 11:45 AM, Roger Hui <rogerhui.can...@gmail.com>
>>> wrote:
>>>
>>> That's my alternative faster expression as well. But the more
>>>> interesting
>>>> question is, why is it faster? Since we do the grade in both cases,
the
>>>> comparison is between /:~x and g{x (or x{~g) with g pre-computed. The
>>>> answer does not depend knowledge specific to J.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Wed, Mar 5, 2014 at 11:38 AM, Joe Bogner <joebog...@gmail.com>
>>>> wrote:
>>>>
>>>> Sorting and grading separately seems faster
>>>>>
>>>>> timer=: 6!:2
>>>>> x=:(1e7 $ 26?26) { 'abcdefghijklmnopqrstuvwxyz'
>>>>> NB. incumbent
>>>>> timer 's=: x{~g=: /:x'
>>>>> 0.0914002
>>>>>
>>>>> NB. alternate
>>>>> timer 'S=: /:~x[G=: /:x'
>>>>> 0.0668677
>>>>>
>>>>> s-:S
>>>>> 1
>>>>> G-:g
>>>>> 1
>>>>>
>>>>>
>>>>> I am speculating that sorting does it in place? which is faster than
>>>>> the selection from the grade
>>>>>
>>>>>
>>>>>
>>>>> On Wed, Mar 5, 2014 at 2:02 PM, Raul Miller <rauldmil...@gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Hmm...
>>>>>>
>>>>>> G=:a.i.S=:/:~x
>>>>>> is faster.
>>>>>>
>>>>>> But while s-:S, g and G are different.
>>>>>>
>>>>>> So I'm drawing a blank here, on how to make the grade.
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> --
>>>>>> Raul
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Wed, Mar 5, 2014 at 1:52 PM, Roger Hui <rogerhui.can...@gmail.com>
>>>>>>
>>>>> wrote:
>>>>>
>>>>>> Suppose x is a long vector of characters and you need both its sort
>>>>>>>
>>>>>> and its
>>>>>
>>>>>> grade. Can you do it faster than s=: x{~g=: /:x ?
>>>>>>>
>>>>>>> Posed this way, the answer is of course yes. But how, and why is it
>>>>>>> faster?
>>>>>>> ------------------------------------------------------------
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