Re: [eigen] Re: JacobiSVD and heap allocations

[Benoit Jacob <jacob.benoit.1@xxxxxxxxx>]

2011/3/2 Adolfo Rodríguez Tsouroukdissian <adolfo.rodriguez@xxxxxxxxxxxxxxxx>:
>
>
> 2011/2/28 Adolfo Rodríguez Tsouroukdissian
> <adolfo.rodriguez@xxxxxxxxxxxxxxxx>
>>
>> Hello,
>>
>> Now that 3.0 is fast approaching, I took a moment to play around with the
>> new implementation of the JacobiSVD (Eigen3 beta 4). The first and most
>> important thing I noticed is that the problem size constructor no longer
>> preallocates all of its resources. Example code:
>>
>> MatrixXd A = MatrixXd::Random(rows, cols);
>> Eigen::JacobiSVD<MatrixXd> svd(rows, cols, Eigen::ComputeThinU |
>> Eigen::ComputeThinV); // Performs 4 allocations
>> svd.compute(A); // Performs 7 allocations, but does not compute U nor V!
>> svd.compute(A, Eigen::ComputeThinU | Eigen::ComputeThinV); // Performs 8
>> allocations.  Does compute U and V
>>
>> All (undesired) allocations performed by compute() take place in lines
>> 558-559 of JacobiSVD:
>>
>> if(!internal::qr_preconditioner_impl<MatrixType, QRPreconditioner,
>> internal::PreconditionIfMoreColsThanRows>::run(*this, matrix)
>>   && !internal::qr_preconditioner_impl<MatrixType, QRPreconditioner,
>> internal::PreconditionIfMoreRowsThanCols>::run(*this, matrix))
>>
>> I ticketed this as issue 206.
>>
> It turns out that I did manage to find some time and propose a patch for
> this issue.
>
>>
>> Secondly, I was expecting svd.compute(A) to use the computationOptions
>> passed to the constructor, otherwise why specify them in advance?.
>
> I'd still like to hear something on this one :)

Hi, sorry for the late reply, I've now replied on bug 206, let's
continue the discussion there.

Benoit