Hi，
I want to solve AT+BFT^4=C (1),
A, B, F are sparse matrix, T, T^4 are the solution vector.
By Newton method, we need to (1) derivation.
So I want to know how to get A.
Or what do you think of solving this equation?
best，
FU
在 2018年11月15日星期四 UTC+8下午10:45:24，Jean-Paul Pelteret写道：
>
> Hi,
>
> In general there is, to the best of my knowledge, no easy answer to your
> question. Can you explain what you intend to do with the matrix “A"? That
> would help a great deal, as there may still be some functionality in the
> library to help you. If you intend to perform some operations with “A” then
> we have some wrapper classes called LinearOperators that can produce an
> effective “A” (without computing it directly). But whether or not this
> makes sense depends on the context in which you want to use “A”.
>
> Best,
> Jean-Paul
>
> On 15 Nov 2018, at 15:28, FU <fudany...@gmail.com <javascript:>> wrote:
>
> Thank you very much for your reply.
>
> I probably understand the methods you mentioned, but there is no
> multiplication vector behind the sparse matrix of the solution I asked for.
>
> A=M- (N^T) (M^-1) N,
>
> This is the construction equation of the original sparse matrix.
>
> A is the sparse matrix that I want to get in the end, where N and M are
> sparse matrices.
>
> What else can you do to solve this problem?
>
> Thank you
>
> FU在 2018年11月14日星期三 UTC+8下午2:32:03，Jean-Paul Pelteret写道：
>>
>> Hi,
>>
>> To compute the sparse matrix inverse M^{-1} you would have to use a
>> direct solver such as SparseDirectUMFPACK
>> <https://dealii.org/9.0.0/doxygen/deal.II/classSparseDirectUMFPACK.html>.
>> If this operation (M^{-1})N appears in the context of matrix-vector
>> products, i.e. you’re actually computing something like y = (M^{-1})Nx then
>> you could use an iterative solver
>> <https://dealii.org/9.0.0/doxygen/deal.II/classSolverSelector.html> to
>> invert the system My = (Nx) = b. Here you could be computing the solution y
>> = M^{-1}b using an iterative method.
>>
>> I hope that this helps.
>> Best,
>> Jean-Paul
>>
>> On 14 Nov 2018, at 03:01, FU <fudany...@gmail.com> wrote:
>>
>> (M^-1)N,
>> M and N are sparse matrix,
>> so how to get the inverse of a sparse matrix?
>>
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