vecgcd

Computes the GCD of the elements of the integer vector V.

Description

G = VECGCD(V) is the greatest common divisor of the elements of the integer
vector V. V must be a row or a column vector of integers.We define gcd([]) = 1 and gcd([0 0 ... 0]) = 0.

I believe that this routine is faster than recursively computing GCDs and the algorithm is simple enough to be used for pencil and paper calculations.

• MATLAB release: MATLAB 7.2 (R2006a)

[Peter Cotton]

typo on line 47?

[Alex]

I took a look and made some quick modifications to speed up the loop.

current_gcd = 0;
for i = 1: length(v)
loop_gcd = mod(v(i), current_gcd);
if(loop_gcd > 0)
  currernt_gcd = loop_gcd;
end
end

This reduces your computation time by about 1/3 for small vectors. I imagine this will increase with larger vectors, because you do not run into issues where the v vector is increasing in size as the while loop continues. Also, as the above commenter noted, you have a line that should be commented out (e x = g).

Also, this adjustment means that it doesn't matter if it is a row or column vector.

[Alex]

I noted a mistake in my above code. the following line should go before the other code.

v = abs(sort(v, 'descend'));