[hdf-forum] How best to model objects that have lists of sub objects.

[Richard Corden]

Hi Quincey,


Quincey Koziol wrote:
> Hi Richard,
>
> On Jun 18, 2009, at 3:36 PM, Richard Corden wrote:
>
>> Hi,
>>
>> I am unable to find a satisfactory way to model object hierarchies, 
>> specifically something as follows:
>>
>> class B { ... };
>>
>> class A {
>> std::vector <B> m_b;
>> };
>>
>>
>> Here are some of my requirements:
>>  * The number of B's is relatively small, probably lower than 10
>>  * There's no upper bound
>>  * It needs to be possible to append data later
>>  * The order the items are written needs to be preserved
>>
[...]

>     Have you tried creating a group for each 'A' and making each 'B' a 
> dataset with an unlimited 1-D dimension, with a datatype that matches 
> 'B' in memory?  Then, each vector of 'B' elements can be easily 
> extended and appended to in an independent way.

I haven't tried this yet, but it will have to be a last resort as I've 
invested quite a bit of time designing a framework based on HDF5 where 
each object is a dataset row.  (FYI, I've written reader/writer objects 
where the interface uses tuples from the boost library (www.boost.org).  
Each part of the tuple has an identifier and a value, which write out as 
if it was a HDF Compound type).

I've managed to work around the size problem by storing the start and 
end indexes rather than references.  I always know the dataset that it 
refers to so that information wasn't required.  So far, read/write times 
are good and file size is good too.

Thanks for your help!

Cheers,

Richard



>
>     Quincey
>


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