Re: [boost] interest in structure of arrays container?

On 2016-10-15 10:14, Michael Marcin wrote:

On 10/14/2016 11:32 PM, degski wrote:

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On 15 October 2016 at 05:43, Michael Marcin wrote:

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Does this already exist somewhere?

Take a look at Boost.DoubleEnded 1 http://erenon.hu/double_ended/ and see whether boost::double_ended::batch_deque http://erenon.hu/double_ended/double_ended/design_rationale.html#double_ende... fills all of your requirements.

Sorry I think I wasn't clear.

Let me back up a bit and give some examples.

Arrays of Structures is the normal programming model.

Let's take a toy example, say I'm looking at some census data and have a structure that looks like:

struct citizen_t { string first_name; string last_name; int salary; int age; };

Then the Array of Structures container would be: vector aos_citizens;

The Structure of Arrays version of the same data would look like:

struct soa_citizens_t { vector<string> first_names; vector<string> last_names; vector<int> salary; vector<int> age; };

soa_citizens_t soa_citizens;

Hi, We implemented something similar for our software. Our usecase was: "when we have a batch of inputs to process, what is the most efficient way to store them such that we can process them with a fast batch algorithm". For example a batch of vectors is a matrix with vectors stored row-wise (and sparse vectors are a sparse matrix). Similarly, if we have pairs of inputs and outputs a batch of those pairs are pairs of batches, tuples of batches, etc. The problem starts when we look at "how do i get an element from a batch?". A matrix-row is not the same as a vector. Moreover, it is unnatural to see a matrix as "batch of rows" (e.g. why not "batch of columns"?) and thus we likely do not have a way to get a row using op[] or iterate over its rows. It becomes only more complicated when looking at a pair of vectors example (a single element of that would be a pair of two matrix-rows) etc. Even after some working on this, we have not really found a stable and "good" solution that does not involve massive amounts of preprocessor boilerplate and massive use of traits classes. I would like to see your take on this, maybe this could give us some way to improve our work! Best, Oswin