I don't think a tacit version can be this fast and still be as readable.
That said, it is possible to delete a line from this implementation.
Sadly, that was the fastest line, so no speedup:
cs1=: 3 : 0
m=. >./y
for_i. }.>:i.n=. #y do.
m=. m>.q=. i*>./y=. 2<./\y
if. (m*i)>:n*q do. break. end.
end.
)
(Also, for tutorial value - the break. can be replaced with return. as
they are equivalent in this context. Put differently: the value
returned by an explicit verb is that of the last non-test statement
which was executed.)
Thanks,
--
Raul
On Sun, Jun 25, 2017 at 9:10 AM, Louis de Forcrand <[email protected]> wrote:
> Here is Mike’s version with 2<./\ inserted (and >./i* replaced by i*>./ since
> i is positive):
>
> cs1=: 3 : 0
> m=. >./y
> for_i. }.>:i.n=. #y do.
> m=. m>.q=. i*>./y=. 2<./\y
> if. (m*i)>:n*q do. break. end.
> end.
> m
> )
>
> 1e3 ts'cs1 qq'
> 0.00107603 29440
> qqq=: 1e4?.1e6
> ts'cs1 qqq'
> 0.045429 398080
> ts'cs qqq'
> 0.180366 397440
>
> Real fast!
> Louis
>
>> On 25 Jun 2017, at 14:47, Louis de Forcrand <[email protected]> wrote:
>>
>> Let V be a vector of real numbers, and V[i] its ith component.
>> Then
>>
>> min( V[i] … V[j+1] ) = min( min( V[i] … V[j] ), min( V[i+1] … V[j+1] ) ).
>>
>> This version is based on that:
>>
>> ms=: #\ >./ . * [: >./@> # 2&(<./\&.>)&< ]
>> 1e3 ts 'ms qq'
>> 0.00491435 5.74234e6
>>
>> Incorporating this in Mike's explicit version with an early stopping
>> condition
>> could lead to even faster runtimes!
>>
>> Cheers,
>> Louis
>>
>>> On 25 Jun 2017, at 11:00, 'Mike Day' via Programming
>>> <[email protected]> wrote:
>>>
>>> There must be something about breakfast.
>>> A loopy stopping condition has just presented itself. Others might see a
>>> tacitisation:
>>>
>>> cs =: 3 : 0
>>>
>>> m =. >./y
>>>
>>> for_i. }.>:i.n =. #y do.
>>>
>>> m =. m >. q =. >./ i ([ * <./\) y
>>>
>>> if. (m * i) >: n * q do. break. end.
>>>
>>> end.
>>>
>>> m
>>>
>>> )
>>>
>>> q holds the maximum area at "width" i . No subsequent area
>>>
>>> can be greater than q*n%i where n is the maximum width, so
>>>
>>> stop if that is no greater than the current maximum, m.
>>>
>>> It's twice as fast and uses slightly less space than c, the loopy verb
>>>
>>> without an early stopping condition:
>>>
>>> ts'c qq'
>>>
>>> 0.014258 21632
>>>
>>> ts'cs qq'
>>>
>>> 0.0044897 21504
>>>
>>> ts'C qq' NB. Raul's best tacit version - so far...
>>>
>>> 0.00803071 289920
>>>
>>> Now for lunch,
>>>
>>> Mike
>>>
>>>
>>> On 24/06/2017 20:09, Raul Miller wrote:
>>>> True, except that if you did not have the inner >./ the "0 1 would not
>>>> help.
>>>>
>>>> Thanks,
>>>>
>>>
>>>
>>>
>>> ---
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