Re: [Boost-users] [MultiArrrat] Unbalanced multi_array<>

Subject: Re: [Boost-users] [MultiArrrat] Unbalanced multi_array<>
From: Pierre-Andre Noel (noel.pierre.andre_at_[hidden])
Date: 2011-09-07 13:34:29

No, Boost.MultiArray is not what you are looking for.

Boost.MultiArray is for data organized as a multi-dimensional "box": each of
its dimension has a specified size. In 3D, these can be understood as
height, width and length. Memory is allocated for every possible elements
within this box, no exception.

> a00 a01 a02 a03 a04 a05 a06 a07 a08
> a10 a11 a12 a13 a14
> a20 a21 a22
> a30 a31
> a40

For your 2D example, you could use a vector of vector.

std::vector< std::vector< my_type > > storage(5); // Your example has 5
lines.
storage[0].resize(9); // The first line of your example has 9 elements.
storage[1].resize(5); // The second line of your example has 5 elements.
storage[2].resize(3); // ...
storage[3].resize(2);
storage[4].resize(1);

If your data is organized according to a "simplex" topology (the
multi-dimensional extension of a triangular matrix, see
http://en.wikipedia.org/wiki/Simplex ), then I may have something for you.
Contact me again and I will give you further information. However, from your
example, I guess that this is not the case.

Pierre-André Noël

2011/9/7 Júlio Hoffimann <julio.hoffimann_at_[hidden]>

> Dear all,
>
> By reading Boost.MultiArray docs, i haven't figured out any possible way to
> deal with unbalanced matrices. The following picture explains what i mean by
> unbalanced:
>
> // two dimensional unbalanced matrix:
>
> a00 a01 a02 a03 a04 a05 a06 a07 a08
> a10 a11 a12 a13 a14
> a20 a21 a22
> a30 a31
> a40
>
> Each row has it's own extent (defined at runtime). Seems multi_array<>
> classes are not designed to increase it's subcontainers decoupled, and at a
> given depth, they always share the same extent? Could you confirm or guide
> me in how to achieve this behavior? I really need to save memory due to
> large 3D matrices.
>
> Regards,
> Júlio.
>
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