mp=: 4 : '+/ .*/ (+/ .*~)^:(I.|.#:y) x'
(2 2$1 1 1 0x) mp 50
20365011074 12586269025
12586269025 7778742049
+/ .*/50 2 2$1 1 1 0x
20365011074 12586269025
12586269025 7778742049
On Fri, Oct 4, 2013 at 12:15 PM, Henry Rich <[email protected]> wrote:
> If you have big powers or big matrices you might want to use the
> repeated-squaring trick, something like
>
> mpwr =: 4 : 'p =. x for_i. }. #: y do. p =. x mp^:i p mp p end.'
>
> fails for y <: 0
>
> Henry Rich
>
>
> On 10/4/2013 12:26 PM, km wrote:
>
>> Verb mpwr calculates matrix powers . Is there a tacit way?
>>
>> mp =: +/ . * NB. matrix product
>>
>> mpwr =: 4 : 'x mp^:y =i.#x' NB. square matrix x to integer power y
>>
>> A =: 1 1 ,: 1 0
>>
>> A
>> 1 1
>> 1 0
>> A mpwr 3
>> 3 2
>> 2 1
>> A mp A mp A
>> 3 2
>> 2 1
>> A mpwr _1
>> 0 1
>> 1 _1
>> A mp A mpwr _1
>> 1 0
>> 0 1
>>
>> --Kip Murray
>>
>> Sent from my iPad
>>
>> ------------------------------**------------------------------**
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>>
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> ----------
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