Re: [Boost-users] Re: dynamic boost::array and performance/size of STL vector

From: Lorenzo Bolla (bolla_at_[hidden])
Date: 2004-06-15 02:38:25

have you had a look at the boost::numeric::ublas::vector?
you can specify a "storage" class to keep the data (for example a simple
pointer to raw memory allocated with "new []") and it keeps a "size_"
internal variable (to improve performance, I suppose).

check:
boost/numeric/ublas/vector.hpp for class vector
boost/numeric/ublas/storage.hpp for class unbounded_array

hope this helps.
lorenzo.

On Tue, Jun 15, 2004 at 01:11:05AM -0500, Bo Peng wrote:
> On Mon, Jun 14, 2004 at 10:51:12PM -0700, Victor A. Wagner Jr. wrote:
> > that's the answer on YOUR implementation...do NOT make assumptions about 
> > how all are implemented.
> 
> I am aware of this. The implementation I checked is for gcc 3.2.2.
> However, there has to be some overheads (several pointers at least) in 
> any vector implementation. Something between boost::array and 
> std::vector can be useful. 
> 
> What is in my mind is a version of boost::array that can has 0 or a 
> fixed length. It might look like: 
> 
> template<class T>
> class carray {
> public:
>   size_t N;
>   // if carray is created by carray(n,elem), do not have ownership to elems.
>   T* elems;
>   // constructor
>   carray():N(0),elems(NULL){}
> 
>   // create array
>   carray(size_t size):N(size){
>     elems = new T[size];  
>   }
>   // destructor
>   ~carray(){
>     if(elems!=NULL) delete[] elems;
>   }
>   // copy constructor, 
>   // can copy from carray, boost::array or vector
>   ...
>   // maybe some constructors as those in vector (vec(ptr1, ptr2))
>   // or things like carray(int n, T* t) to assemble carray 
>   // from existing array t without copying things...
>   ...
>   // resize, can be called only when N=0.
>   resize(int n){ .... }
> 
>   // iterators and everything else can be copied directly
>   // from boost::array.
> 
> }
> 
> Bo 
> 
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