matrix and fibonacci

[sclytrack]

On 03/09/2012 10:51 AM, newcomer[bob] wrote:
> On Friday, 9 March 2012 at 09:22:47 UTC, newcomer[bob] wrote:
>> On Friday, 9 March 2012 at 05:50:03 UTC, newcomer[bob] wrote:
>>> The following is a matrix implementation of the fibonacci
>>> algorithm:
>>>
>>> int fib(int n)
>>> {
>>> int M[2][2] = {{1,0},{0,1}}
>>> for (int i = 1; i < n; i++)
>>> M = M * {{1,1},{1,0}}
>>> return M[0][0];
>>> }
>>>
>>> problem is I don't really understand how matrix multiplication
>>> works so i cannot translate it to an equivalent solution in D.
>>> Thank for you assistance in advance.
>>>
>>> newcomer[bob]
>>
>> I attempted the following but it does not work:
>>
>> int fib(int n)
>> long[2][2] M = [[1,0], [0,1]];
>> ulong[2][2] C = [[1,1], [1,0]];
>> foreach (i; 0 .. n) {
>> M[0][0] = M[0][0] * C[0][0] + M[0][0] * C[0][1];
>> M[0][1] = M[0][1] * C[0][1] + M[0][1] * C[1][1];
>> M[1][0] = M[0][1] * C[0][0] + M[1][1] * C[0][1];
>> M[1][1] = M[1][1] * C[0][1] + M[1][1] * C[1][1];
>> }
>> return M[0][0];
>> }
>>
>> any ideas what I'm doing wrong?
>>
>> Thanks,
>> Bob
>
> Turns out that this this is an algorithm for calculating the
> powers of two up to 2^63. I still cannot find how to modify it to
> produce the fibonacci sequence though. Any advice would be
> appreciated.
>
> Thanks,
> Bob

http://en.wikipedia.org/wiki/Matrix_multiplication#Non-technical_example

http://en.wikipedia.org/wiki/Fibonacci_number#Matrix_form


I don't understand what you are trying to do above.