Re: Looping over ordered partitions

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

On Tue, Feb 06, 2024 at 11:46:55AM -0500, Charles Greathouse wrote:
> The looping commands force and forpart are very convenient. I have a
> problem I was working on which is looking for the smallest vector (in terms
> of vecsum) with a certain property. What is the best way to perform such a
> search in PARI/GP?
> 
> In my case I have dimension/vector length 11 and sum < 31. (I have an
> instance with sum 31 but it's probably not optimal.)
> 
> I can do a forvec, but even forvec(v=vector(11,i,[1,7]), ...) takes a long
> time (and spends a lot of time looking at values with sum > 30), and I miss
> instances with numbers larger than 7. Or else I can use forpart but then I
> need to permute the values (and in my case I definitely have duplicate
> values, so naive 11! permutations are wasteful and slow).

Use forpart + forperm!

forpart(x=30,forperm(x,p,print(p)),,[11,11])

Cheers,
Bill.