Re: [Toon-members] Dynamic Matrix allocation in an iteration loop?

[Gerhard Reitmayr]

Hi,

if you are worried about the overhead of memory allocation, then you could 
allocate a large matrix and then use for example a dynamical slice inside the 
loop. or make a reference matrix which you point at some preallocated array of 
data. small dynamic matrices might be allocated on the stack anyway, so not 
real overhead compared to a static one...

using a resizable will not change as it will also allocate on resize (I think ?)

I would ask myself first, if the allocation is really a bottle neck. Always 
measure first, before attempting optimization! it might not really make a 
difference in your program. So profile your function, program etc. first and 
see if this allocation takes an inappropriate amount of time.

cheers,
  Gerhard

On 22 Mar 2010, at 18:25, ETH wrote:

> Hello TooN Members
> 
> I have a simple question:
> I have an iteration loop in which my matrix e.g A is always size dependend, 
> for example in one iteration its  9 x 3 in another its 9x16 and so on.
> The problem facing TooN is that I always make new dynamical Matrices for this 
> purpose but this is probably stupid because I always allocate  new memory in 
> each iteration?
> 
> Is there an efficient way to reduce allocation here?   By a Matrix <...,..., 
> Reference>?
> Or should I use Resizable Matrices?
> 
> Can someone help?
> 
> Thanks a lot!!
> 
> 
> 
> 
> Am 20.03.2010 um 17:01 schrieb address@hidden:
> 
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>> Today's Topics:
>> 
>>  1.  NEW(with code) : Implementation of BaseClass with       virtual
>>     template functions with TOON (Gabriel N?tzi)
>> 
>> 
>> ----------------------------------------------------------------------
>> 
>> Message: 1
>> Date: Fri, 19 Mar 2010 17:46:08 +0100
>> From: Gabriel N?tzi <address@hidden>
>> Subject: [Toon-members] NEW(with code) : Implementation of BaseClass
>>      with    virtual template functions with TOON
>> To: address@hidden
>> Message-ID: <address@hidden>
>> Content-Type: text/plain; charset="us-ascii"
>> 
>> (Here again because source code was missing)
>> 
>> Hello all,
>> 
>> I have a basic question where I am completely stuck with TooN:
>> I dont know how to realize this:
>> 
>> I have a DynamicSystem Class which describes a Dynamical System with 
>> template parameter <int NDOF>
>> I would like to have a Class Solver which has a reference to an instance of 
>> DynamicSystem.
>> The solver should be able to call several virtual functions from 
>> DynamicSystem. (subClass could be a Ball or a Car or what ever :-))
>> The main problem is that this main functions take Vectors/Matrices as Input 
>> and give Vector and Matrices as Output back (depending on NDOF)
>> but when I want to properly define such a function in TOON i need templates 
>> (to be able to input also slices and so on....)
>> 
>> like 
>> 
>> template<typename BaseM, typename BaseV>
>> Matrix<3,3,double,BaseM> get_M (double t, Vector<3,double, BaseV > x   ){
>>              // some code
>>      }
>> 
>> But the problem is that in C++ we can not define templates as virtual 
>> functions......
>> (SEE ATTACHED SIMPLE CODE!!)
>> 
>> HOW DO I SOLVE this Problem with TooN?
>> How should I structure my Classes? Would be very helpful if someone can 
>> quickly append the changes in the attached source code (ITS SIMPLE :-))!
>> 
>> Thank you very much for your HELP!!
>> 
>> 
>> =========================================CODE======================================================
>> 
>> 
>> 
>> #include <iostream>
>> #include <TooN/TooN.h>
>> 
>> using namespace std;
>> using namespace TooN;
>> 
>> template<int NDOF>
>> class DynamicSystem {
>>      
>> public:
>>      DynamicSystem(){
>>      };
>>      ~DynamicSystem(){
>>      };
>>      
>>      virtual Matrix<NDOF,NDOF> get_M(double t, Vector<NDOF> x)=0;
>> 
>> private:
>>      int ndof;
>>      
>> };
>> 
>> class WoodPecker : public DynamicSystem<3>{
>>      public:
>>      WoodPecker(){
>>      };
>>      ~WoodPecker(){
>>      };
>> 
>>      Matrix<3,3> get_M(double t, Vector<3> x){
>>              Matrix<3,3> A =Identity;
>>              return A;
>>      }
>> };
>> 
>> template<int NDOF>
>> class Solver{
>> public:
>>      Solver(DynamicSystem<NDOF> & myref): ref(myref) {
>>              
>>      };
>>      ~Solver(){
>>      };
>>      DynamicSystem<NDOF> & ref;
>>      
>>      void dosome(){
>>              Vector<> a(NDOF);
>>              cout << ref.get_M(0,a) <<endl; //works
>>              // cout << ref.get_M(0,a.slice<>(1,NDOF)) <<endl; // does not 
>> work..... (shit) :-)
>>      }
>> };
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>> End of Toon-members Digest, Vol 43, Issue 2
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> 
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--
Gerhard Reitmayr
Institute for Computer Graphics and Vision
http://www.icg.tugraz.at/Members/gerhard
tel: ++43 316 873 5082