Re: [boost] Interest in a container which can hold multiple data types?

2015-05-06 20:58 GMT+08:00 Joaquin M Lopez Munoz :

Boris Rasin writes:

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On 5/5/2015 7:49 PM, Joaquin M Lopez Munoz wrote:

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TONGARI J writes:

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If the data sequence shows some affinity, I guess an ordered tuple_vector-based sequence can provide some performance benefit in traversal (with some crafted for_each method).

That is, a sequence of [AAABBB] may be traversed faster than [ABABAB]

for

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such a container, and I believe in the later case such that the types are uniformly distributed, vector<variant> will perform better. I wrote something on this some time ago, maybe worth having a look at:

http://bannalia.blogspot.com/2014/05/fast-polymorphic-collections.html

http://bannalia.blogspot.com/2014/05/fast-polymorphic-collections-with.html

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Interesting read, thanks for the links. Although in this case we are talking about vector<variant> which stores data by value.

Ok, understood. I've written a small performance test of vector> and sorted vector> vs. a collection class het_collection storing values of the same type contiguously and providing a specialized for_each memfun:

https://www.dropbox.com/s/qy9qbf0eyf1itsy/het_collection.cpp?dl=0

Timing for for_each on 1k-10M elements (MSVC 12.0):

het_collection;vector_variant;sorted_vector_variant; for_each: 1000;0.0225453;0.0822232;0.0840048; 10000;0.0229827;0.0828214;0.0821378; 100000;0.0229448;0.081315;0.0839802; 10000000;0.0250193;0.0906496;0.0879296;

So, unsurprisingly, het_collection does much better as for_each on a vector<variant> needs to check type on each iteration. Sorting the vector so that values of the same type lie together does not have any impact on performance.

In case that you misunderstood my previous post, the assumption that when values of the same type lie together could result in better performance was for ordered tuple_vector-based sequence, not for vector_variant. Your benchmark result is indeed what we expected, what I'd like to see is the comparison between *ordered* het_collection and vector_variant.