Re: [Boost-users] multi-array and pdes

Hi Pierre-Andre, Thank you for your response. For a moment, I thought that the cyclic_storage_order was already avail.. A question: why does it have to derive for the general_storage class? there is the implicit conversion operator, no? I did something like: class cyclic_storage_order { typedef detail::multi_array::size_type size_type; public: cyclic_storage_order( const std::size_t shift ) :shift_(shift) {} template operator general_storage_order<NumDims>() const { boost::array ordering; boost::array ascending; for (size_type i=0; i != NumDims; ++i) { ordering[i] = (i+shift_)%NumDims; ascending[i] = true; } return general_storage_order<NumDims>(ordering.begin(), ascending.begin()); } private: std::size_t shift_; }; Is this what you meant? Thank you very much for all your help, P- ---- Pierre-Andre Noel wrote:

I forgot a detail: once you got your "cyclic_storage_order", you should make a normal multi_array as usual then access it through a multi_array_ref that uses "cyclic_storage_order".

On Sun, May 22, 2011 at 12:17 PM, Pierre-Andre Noel < noel.pierre.andre@gmail.com> wrote:

...

Hello Petros,

I think that what you are looking for is a different storage order.

Take a look at "boost/multi_array/storage_order.hpp". 3 classes are defined: general_storage_order, c_storage_order and fortran_storage_order.

You need to make a "cyclic_storage_order" (or something like that) that receives an integer. When receiving zero, it should behave like c_storage_order. When receiving 1, everything should be permuted by 1 etc. This new class should inherit from general_storage_order. Use c_storage_order and fortran_storage_order as examples.

Keep "ascending" true, only "ordering" has to be changed. A modulo should do it.

Hope it helps,

Pierre-André Noël

On Sun, May 22, 2011 at 11:53 AM, petros wrote:

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Hi Larry, apologies, for not being clear. Yes, MA is boost::multi_array. M, N, L are the dimensions (this is only a "logical" statement, rather than a proper code snippet). I think I have pretty much sorted out the calling practices wrt multi-aray and looking for if certain functionality exists. My problem amounts to having a view that would allow for the permutation (if not rotation) of axes. As I begun to explain, the operator splitting methods decompose a problem in N dimensions into N 1-dimensional problems. The problem itself is stated, though, in a certain reference system (this means that the discretized operators (stencils) and the boundary conditions are expressed in terms of these boundary conditions. However, the linear equation systems that are produced, are in tridiagonal form, only in one of these steps ( the first step of the 1-D problems ). Otherwise it produces a block-banded system of equations, that can be reduced back to the familiar tridiagonal ( conceptually), through axes permutation (or rotation). If one things in terms of the 2D problem analog, while conceptually it would amount to exchange the two axes, in matrix form, and because of the storage alignment it would involve a much bigger operation. Since, these operators/systems are created from the problem, it would be very nice to have this view functionality to exploit for keeping the storage of the operators in the desired form.

I hope this is clearer now - don't mean to drag you into my problem. Thank you for your response, Petros

-----Original Message----- From: Larry Evans Sent: Sunday, May 22, 2011 10:43 AM To: boost-users@lists.boost.org Subject: Re: [Boost-users] multi-array and pdes

On 05/21/11 15:02, petros wrote: Hi Petros,

[snip]

...

Suppose then that I have a MA( M, N, L ):

Please be more specific. I assume:

MA means boost::multi_array

however, I've no idea what M, N, and L are. Could you please explain further?

-regards, Larry

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