# Pseudo Inverse of singular matrix
**URL:** https://community.freefem.org/t/pseudo-inverse-of-singular-matrix/230
**Category:** General Discussion
**Created:** [January 29, 2020, 5:19pm UTC](https://community.freefem.org/t/pseudo-inverse-of-singular-matrix/230 "2020-01-29T17:19:04Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@hraf5](https://community.freefem.org/u/hraf5)
#### Post date: [January 29, 2020, 5:19pm UTC](https://community.freefem.org/t/pseudo-inverse-of-singular-matrix/230/1 "2020-01-29T17:19:04Z")
Hello every one,
How to calculate the pseudoInverse of a singular matrix with FreeFem++?
Best regards.
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### Author:  [@prj](https://community.freefem.org/u/prj)
#### Post date: [January 29, 2020, 5:29pm UTC](https://community.freefem.org/t/pseudo-inverse-of-singular-matrix/230/2 "2020-01-29T17:29:54Z")
Uset PETSc, with the following options: `-pc_type lu -pc_factor_mat_solver_type mumps -mat_mumps_icntl_24 1`. The pseudo-inverse is not unique, this will compute _a_ pseudo-inverse inverse. You can lookup the option ICNTL(24) from the MUMPS [guide](http://mumps.enseeiht.fr/doc/userguide_5.2.1.pdf).
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### Author:  [@hraf5](https://community.freefem.org/u/hraf5)
#### Post date: [February 6, 2020, 11:15am UTC](https://community.freefem.org/t/pseudo-inverse-of-singular-matrix/230/3 "2020-02-06T11:15:15Z")
Hello prj,
First of all, I would like to thank you for your response.
I tried to work with the PETSc package. I wrote the code below, but I can’t upload the PETSc package. Could you please tell me how to upload the PETSc package and if possible tell me your opinion about the code?
Thank you very much.
_Code :_
load “PETSc”
// Matrix
int n = 16;
real[int, int] MM(n, n), A(n, n);
cout \<\< "read the matrix MM "\<\< endl;
{
ifstream file1(“MM.dat”);
for(int i=0;i\<16 ; i++){
for(int j=0;j\<16 ; j++){
file1 \>\> MM(i,j) ;
}
}
}
//Compute the Pseudo inverse of MM
set(MM, sparams = “-pc\_type lu -pc\_factor\_mat\_solver\_type mumps -mat\_mumps\_icntl\_24 1”);
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### Author:  [@prj](https://community.freefem.org/u/prj)
#### Post date: [February 6, 2020, 11:51am UTC](https://community.freefem.org/t/pseudo-inverse-of-singular-matrix/230/4 "2020-02-06T11:51:11Z")
The code looks good. You probably don’t have the `PETSc` package installed with FreeFEM. You need to fix that of you want to compute pseudo-inverses.
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### Author:  [@tea](https://community.freefem.org/u/tea)
#### Post date: [November 8, 2024, 1:00pm UTC](https://community.freefem.org/t/pseudo-inverse-of-singular-matrix/230/6 "2024-11-08T13:00:04Z")
Hello prj,
is there a way to compute the pseudo-inverse which gives the solution with the smallest norm?
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### Author:  [@prj](https://community.freefem.org/u/prj)
#### Post date: [November 10, 2024, 8:56am UTC](https://community.freefem.org/t/pseudo-inverse-of-singular-matrix/230/7 "2024-11-10T08:56:43Z")
With `-pc_type svd`, but that will be extremely slow.