Re: [Cppqed-support] Position correlation

[Raimar S. <rai...@ui...>]

Dear András,

thanks for your reply. So you are saying blitzplusplus::vfmsi::fullRange could 
always only give me the two-particle (left or right) state vector from my 
DensityOperatorLow, this is why I have to use blitzplusplus::basi::fullRange. 
Actually, your code snippet is pretty much what I also had in mind. 

On a related note, would it be possible that, given a 
blitzplusplus::basi::Iterator with two or more retained index positions, to 
slice it even further? This would somehow be related to the concept that a 
slice of a multi-array is again a multi-array and can be sliced. 

On Wednesday 15 February 2012 11:53:02 Andras Vukics wrote:

> This is actually rather wasteful, because even in the case when the
> underlying data is just a state vector, it is treated in the same way as a
> full density operator. You could maybe think about a nice general solution
> to this problem (I have just added a tracker #3487814 on this issue).

Yes I have noticed the tracker :). So in principle the slicing would occur in 
the fft function, not in the average function anymore. How would such a fft 
function with specialized implementation determine the type of the passed 
LazyDensityOperator, by dynamic_cast?

> // left:
> for_each(fullRange(rhotemp,Vector<0>()),bind(&ffTransform,_1,FFTDIR_KX));
> for_each(fullRange(rhotemp,Vector<1>()),bind(&ffTransform,_1,FFTDIR_KX));
> // right:
> for_each(fullRange(rhotemp,Vector<2>()),bind(&ffTransform,_1,FFTDIR_XK));
> for_each(fullRange(rhotemp,Vector<3>()),bind(&ffTransform,_1,FFTDIR_XK));
> 
> Where Vector stands for tmptools::Vector. (This is not the only class that
> works with the slice iterators, because e.g. boost::mpl::range_c also
> works, but here you need this.)

Wouldn't boost::mpl::range_c<int,0,1>, boost::mpl::range_c<int,1,2> etc work, 
although of course a bit awkward?

Best regards
Raimar