Re: How to remove all cycles
- To: mathgroup at smc.vnet.net
- Subject: [mg98316] Re: [mg98269] How to remove all cycles
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Sun, 5 Apr 2009 06:41:08 -0400 (EDT)
- Reply-to: hanlonr at cox.net
n = 13;
A = Array[a, 2^(n + 1)];
B = Array[b, {2, 2^n}];
Do[Do[A[[j + BitShiftLeft[k - 1, 1]]] = B[[j, k]], {j, 1, 2}], {k, 1,
2^n}] // Timing
{0.616373,Null}
A2 = Flatten[Transpose[B]]; // Timing
{0.008281,Null}
A == A2
True
Bob Hanlon
---- buts <manger31 at yahoo.com> wrote:
=============
Hello,
I want to write the following code using functional
programming, i.e. to remove all Do's.
There are two arrays:
A[[i]], i=1,...,2^(n+1)
B[[j,k]], j=1,2; k=1,...,2^n.
I need to assign B to A setting the first bit of the index i
to be the index j. Explicitly
Do[Do[A[[ j + BitShiftLeft[k-1,1] ]]= B[[j,k]],
{j,1,2}],{k,1,2^n}]
I need to do it for multi-dimensional large arrays.
Is it possible to write it without Do's ?
Thanks.
--
Bob Hanlon