Re: [eigen] Feature idea: coeffRef() ---> setCoeff() |

[ Thread Index | Date Index | More lists.tuxfamily.org/eigen Archives ]

*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] Feature idea: coeffRef() ---> setCoeff()*From*: Manoj Rajagopalan <rmanoj@xxxxxxxxx>*Date*: Fri, 30 Jul 2010 12:56:39 -0400*Organization*: EECS Dept., University of Michigan, Ann Arbor, MI, USA

On Friday 30 July 2010 10:30:19 am Benoit Jacob wrote: > 2010/7/30 Manoj Rajagopalan <rmanoj@xxxxxxxxx>: > > On Friday 30 July 2010 12:08:42 am Benoit Jacob wrote: > >> oh... i see. I guess that you omitted setCoeff in the above line, by > >> the way, so you meant: > >> > >> A.selfadjointView<Lower>().setCoeff(j, j+1, value); // note: write to > >> upper triangle > >> > >> so this would write 2 coeffs at once in A ? Why not. Indeed that cant > >> be done with coeffRef. But I don't adhere to your rather complex plan > >> of generally allowing to write to Conjugate expressions, this is not a > >> prerequisite for that, we could just implement setCoeff in > >> selfadjointView, where it is useful, without implementing it in stuff > >> like conjugate() which IMO just don't want to be writable expressions. > >> > >> This would be much simpler --- the patch could be just a few kB's. > >> > >> But again, coeffRef() is definitely not going away. > >> > >> Benoit > > > > In my implementation of LLT on self-adjoint matrices with compact > > triangular storage, which involves partitioning the matrix into 2x2 block > > form, one step leads to an Eigen expression of the form, > > > > L11.solveInPlace(L21.adjoint()); // L11 is triangular-view > > Oh, if that's what you wanted to do, why don't you just apply complex > conjugation here, so this is equivalent to doing: > > L11.conjugate().solveInPlace(L21.transpose()); > > Now you're good to go, because transpose() returns a writable > expression which can perfectly be used in solve-in-place. > > Benoit > That's exactly what I settled into :-) The wish for a neater, more direct expression closer to the math sparked off this entire line of thought :-) -- Manoj

**Follow-Ups**:**Re: [eigen] Feature idea: coeffRef() ---> setCoeff()***From:*Benoit Jacob

**References**:**[eigen] Feature idea: coeffRef() ---> setCoeff()***From:*Manoj Rajagopalan

**Re: [eigen] Feature idea: coeffRef() ---> setCoeff()***From:*Manoj Rajagopalan

**Re: [eigen] Feature idea: coeffRef() ---> setCoeff()***From:*Benoit Jacob

**Messages sorted by:**[ date | thread ]- Prev by Date:
**Re: [eigen] Expression templates** - Next by Date:
**Re: [eigen] Feature idea: coeffRef() ---> setCoeff()** - Previous by thread:
**Re: [eigen] Feature idea: coeffRef() ---> setCoeff()** - Next by thread:
**Re: [eigen] Feature idea: coeffRef() ---> setCoeff()**

Mail converted by MHonArc 2.6.19+ | http://listengine.tuxfamily.org/ |