# Problem with lyap(Q,R)
**URL:** https://discourse.julialang.org/t/problem-with-lyap-q-r/64745
**Category:** General Usage
**Created:** [July 16, 2021, 12:36pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745 "2021-07-16T12:36:19Z")
**Posts on this page:** 12
**Page:** 1
### Author:  [@ylish](https://discourse.julialang.org/u/ylish)
#### Post date: [July 16, 2021, 12:36pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/1 "2021-07-16T12:36:20Z")
Hello everybody,
I am new to Julia and I am trying to rewrite and improve some code that I have in MATLAB. I have come across something that I cannot fix. Could someone see what the issue is?
I have the following code:
using LinearAlgebra
A = [1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0]
B = [0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; -1252.0 1250.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0; 1250.0 -1252.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.0 0.0 0.0; 0.0 2.0 -1252.0 1250.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.0 0.0; 0.0 0.0 1250.0 -1252.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.0; -1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1252.0 -1250.0 0.0 0.0; 0.0 -1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1250.0 1252.0 -2.0 0.0; 0.0 0.0 -1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -2.0 1252.0 -1250.0; 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1250.0 1252.0; 0.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 0.0]
lyap(Matrix(B’),A)
but I get the following message:
LAPACKException(1)
Stacktrace:
[1] chklapackerror(ret::Int64)
@ LinearAlgebra.LAPACK /buildworker/worker/package\_linux64/build/usr/share/julia/stdlib/v1.6/LinearAlgebra/src/lapack.jl:38
[2] trsyl!(transa::Char, transb::Char, A::Matrix{Float64}, B::Matrix{Float64}, C::Matrix{Float64}, isgn::Int64)
@ LinearAlgebra.LAPACK /buildworker/worker/package\_linux64/build/usr/share/julia/stdlib/v1.6/LinearAlgebra/src/lapack.jl:6463
[3] trsyl!
@ /buildworker/worker/package\_linux64/build/usr/share/julia/stdlib/v1.6/LinearAlgebra/src/lapack.jl:6444 [inlined]
[4] lyap(A::Matrix{Float64}, C::Matrix{Float64})
@ LinearAlgebra /buildworker/worker/package\_linux64/build/usr/share/julia/stdlib/v1.6/LinearAlgebra/src/dense.jl:1567
[5] top-level scope
@ In[17]:4
[6] eval
@ ./boot.jl:360 [inlined]
[7] include\_string(mapexpr::typeof(REPL.softscope), mod::Module, code::String, filename::String)
@ Base ./loading.jl:1094
In MATLAB there is no issue with these two matrices and the same exact comand. Would someone know what the issue could be ? ][=
---
### Author:  [@Sukera](https://discourse.julialang.org/u/Sukera)
#### Post date: [July 16, 2021, 12:55pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/2 "2021-07-16T12:55:26Z")
Welcome! In order to make it easier to help you, please wrap your code in triple backtickes (```) to format it as code. For more information, please read [Make it easier to help you](https://discourse.julialang.org/t/please-read-make-it-easier-to-help-you/14757). Please also make sure you’re aware of the [Differences from MATLAB](https://docs.julialang.org/en/v1/manual/noteworthy-differences/#Noteworthy-differences-from-MATLAB).
I’m not sure why this works in MATLAB in the first place - `B'` has negative complex conjugate eigen values, which are forbidden per the dosctring of `lyap` (or I’m misunderstanding something about the dosctring):
```julia
julia> eigvals(B')
16-element Vector{ComplexF64}:
-0.6761400549933252 - 0.978143841175781im
-0.6761400549933252 + 0.978143841175781im
-0.5754555540509579 - 1.6824830146993683im
-0.5754555540509579 + 1.6824830146993683im
-0.5000999500060193 - 50.007504436433635im
-0.5000999500060193 + 50.007504436433635im
-0.500099870149834 - 50.027497437709776im
-0.500099870149834 + 50.027497437709776im
0.5000998701498371 - 50.027497437709776im
0.5000998701498371 + 50.027497437709776im
0.5000999500060104 - 50.00750443643361im
0.5000999500060104 + 50.00750443643361im
0.5754555540509454 - 1.6824830146993628im
0.5754555540509454 + 1.6824830146993628im
0.676140054993325 - 0.9781438411758407im
0.676140054993325 + 0.9781438411758407im
help?> lyap
search: lyap displayable
lyap(A, C)
Computes the solution X to the continuous Lyapunov equation AX + XA' + C = 0,
where no eigenvalue of A has a zero real part and no two eigenvalues are
negative complex conjugates of each other.
```
---
### Author:  [@zdenek\_hurak](https://discourse.julialang.org/u/zdenek_hurak)
#### Post date: [July 16, 2021, 1:24pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/3 "2021-07-16T13:24:18Z")
You may also want to try some alternative solvers. First, let me - just for convenience - rename your matrices so that they correspond to the common conventions used by solvers. Your `A` will become `C`, your `B` will become `A` after transposition:
```julia
C = [1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0]
A = [0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; -1252.0 1250.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0; 1250.0 -1252.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.0 0.0 0.0; 0.0 2.0 -1252.0 1250.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.0 0.0; 0.0 0.0 1250.0 -1252.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.0; -1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1252.0 -1250.0 0.0 0.0; 0.0 -1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1250.0 1252.0 -2.0 0.0; 0.0 0.0 -1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -2.0 1252.0 -1250.0; 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1250.0 1252.0; 0.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 0.0 0.0; 0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 -1.0 0.0 0.0 0.0 0.0]'
```
Now, I am aware of two alternatives for solving Lyapunov equation:
- [MatrixEquations.jl](https://github.com/andreasvarga/MatrixEquations.jl)
- [ControlMatrixEquations.jl](https://github.com/olof3/ControlMatrixEquations.jl)
```julia
julia> using MatrixEquations
julia> X = lyapc(A,C)
16×16 Matrix{Float64}:
15279.3 -15293.4 12471.6 … -223.391 -119.321 115.15
-15293.4 15299.2 -12479.8 227.77 114.793 -119.321
12471.6 -12479.8 15299.2 114.793 227.77 -223.391
-12455.4 12471.6 -15293.4 -119.321 -223.391 227.961
-2.78533e-12 2.2311e-11 -2.34454e-8 1.21925e-11 -9.91488e-10 9.90487e-10
1.06155e-11 -2.97575e-11 2.34695e-8 … 0.5 9.91008e-10 -9.90498e-10
⋮ ⋱ ⋮
9.78416e-10 -9.78896e-10 -3.18567e-11 9.85301e-12 2.73115e-14 1.40998e-14
227.961 -223.391 -119.321 7.10242 -6.05262 3.9942
-223.391 227.77 114.793 -4.9365 4.00557 -6.05262
-119.321 114.793 227.77 4.00557 -4.9365 7.10242
115.15 -119.321 -223.391 … -6.05262 7.10242 -4.92681
julia> A*X+X*A'+C
16×16 Matrix{Float64}:
3.3527e-8 -3.49999e-8 -1.3459e-9 -9.35604e-10 … 2.41243e-9 -2.72769e-9 4.49009e-9 -2.63853e-9
-3.49999e-8 3.64698e-8 1.17352e-9 1.10988e-9 -2.49065e-9 2.80954e-9 -4.42813e-9 2.57208e-9
-1.3459e-9 1.17352e-9 -4.86263e-8 4.56729e-8 3.24606e-9 -3.6765e-9 4.3874e-9 -2.1422e-9
-9.35604e-10 1.10988e-9 4.56729e-8 -4.27212e-8 -3.22284e-9 3.65187e-9 -4.42378e-9 2.18074e-9
-2.49747e-9 2.48474e-9 -1.66074e-9 1.65346e-9 -7.63123e-11 8.03766e-11 3.14344e-11 -3.66214e-11
5.33328e-9 -5.326e-9 4.77667e-9 -4.77121e-9 … 7.03722e-11 -7.77618e-11 3.45324e-12 5.57066e-12
⋮ ⋱ ⋮
1.88513e-9 -1.88631e-9 1.96059e-9 -1.95914e-9 2.40963e-11 -2.31539e-11 -1.49818e-11 1.37126e-11
2.41243e-9 -2.49065e-9 3.24606e-9 -3.22284e-9 -7.75162e-11 8.55078e-11 1.25947e-10 -1.4731e-10
-2.72769e-9 2.80954e-9 -3.6765e-9 3.65187e-9 8.55078e-11 -9.43823e-11 -1.29694e-10 1.51797e-10
4.49009e-9 -4.42813e-9 4.3874e-9 -4.42378e-9 1.25947e-10 -1.29694e-10 -1.10189e-10 1.43357e-10
-2.63853e-9 2.57208e-9 -2.1422e-9 2.18074e-9 … -1.4731e-10 1.51797e-10 1.43357e-10 -1.77527e-10
```
and
```julia
julia> using ControlMatrixEquations
julia> X = lyapc(A,C)
16×16 Matrix{Float64}:
15279.3 -15293.3 12471.6 … -223.387 -119.323 115.147 -15293.3 15299.2 -12479.8 227.773 114.79 -119.323 12471.6 -12479.8 15299.2 114.79 227.773 -223.387 -12455.4 12471.6 -15293.3 -119.323 -223.387 227.964 -2.61548e-12 2.21302e-11 -2.34452e-8 1.21753e-11 -9.91495e-10 9.90495e-10 1.04541e-11 -2.9604e-11 2.34692e-8 … 0.5 9.91015e-10 -9.90506e-10 ⋮ ⋱ ⋮ 9.78423e-10 -9.78905e-10 -3.18727e-11 9.853e-12 2.7605e-14 1.39602e-14
227.964 -223.387 -119.323 7.10262 -6.0528 3.99402
-223.387 227.773 114.79 -4.93629 4.00538 -6.0528
-119.323 114.79 227.773 4.00538 -4.93629 7.10262
115.147 -119.323 -223.387 … -6.0528 7.10262 -4.92661
julia> A*X+X*A'+C16×16 Matrix{Float64}: 3.36389e-8 -3.51083e-8 -1.50165e-9 -8.36706e-10 … 2.40959e-9 -2.72439e-9 4.48801e-9 -2.64033e-9 -3.50854e-8 3.65519e-8 1.28263e-9 1.05764e-9 -2.48701e-9 2.80511e-9 -4.42472e-9 2.57256e-9 -1.57833e-9 1.30631e-9 -4.85399e-8 4.55455e-8 3.24075e-9 -3.67374e-9 4.38195e-9 -2.14322e-9 -7.61101e-10 1.03502e-9 4.56016e-8 -4.2609e-8 -3.21617e-9 3.64777e-9 -4.42071e-9 2.18392e-9 -2.49929e-9 2.49383e-9 -1.66438e-9 1.6571e-9 -7.63976e-11 8.0405e-11 3.1477e-11 -3.67208e-11 5.3351e-9 -5.32782e-9 4.7803e-9 -4.77485e-9 … 7.05427e-11 -7.78471e-11 3.31113e-12 5.65592e-12 ⋮ ⋱ ⋮ 1.88534e-9 -1.88663e-9 1.96076e-9 -1.95922e-9 2.41025e-11 -2.31735e-11 -1.49392e-11 1.36744e-11
2.41596e-9 -2.49111e-9 3.24749e-9 -3.21498e-9 -7.74358e-11 8.5367e-11 1.25663e-10 -1.47177e-10
-2.72917e-9 2.80772e-9 -3.67852e-9 3.64461e-9 8.53111e-11 -9.41252e-11 -1.29703e-10 1.51957e-10
4.49071e-9 -4.42183e-9 4.38627e-9 -4.41719e-9 1.25676e-10 -1.2959e-10 -1.10448e-10 1.43313e-10
-2.63916e-9 2.5658e-9 -2.14402e-9 2.17699e-9 … -1.47204e-10 1.5186e-10 1.4371e-10 -1.77583e-10
```
---
### Author:  [@fph](https://discourse.julialang.org/u/fph)
#### Post date: [July 16, 2021, 1:30pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/4 "2021-07-16T13:30:41Z")
> [@Sukera](#):
>
> I’m not sure why this works in MATLAB in the first place - `B'` has negative complex conjugate eigen values, which are forbidden per the dosctring of `lyap` (or I’m misunderstanding something about the dosctring):
Maybe I am missing something, but it doesn’t seem that it is the case, to me. “Negative complex conjugate eigenvalues”, in this context, should mean “there are no two eigenvalues such that \lambda\_i + \overline{\lambda\_j} = 0”. Some of those sums are very close to zero, but not exactly equal, it seems to me.
EDIT: I just checked the docs for `dtrsyl.f`, that’s what the error code means:
```julia
* = 1: A and B have common or very close eigenvalues; perturbed
* values were used to solve the equation (but the matrices
* A and B are unchanged).
```
So (1) that INFO value appears even if the eigenvalues are merely close, not exactly equal, and (2) That INFO value alone should not cause a failure, since a valid solution is returned anyway (although this means that the problem is ill-conditioned and the returned solution is likely garbage).
Note that Matlab does not use `trsyl` from Lapack, but routines from Slicot, so it does not run the same code.
---
### Author:  [@Sukera](https://discourse.julialang.org/u/Sukera)
#### Post date: [July 16, 2021, 1:44pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/5 "2021-07-16T13:44:10Z")
I see - in that case, seems like the function handling that “error” is misbehaving here:
From `LinearAlgebra/src/lapack.jl:37`
```julia
function chklapackerror(ret::BlasInt)
if ret == 0
return
elseif ret < 0
throw(ArgumentError("invalid argument #$(-ret) to LAPACK call"))
else # ret > 0
throw(LAPACKException(ret))
end
end
```
And it shouldn’t necessarily always throw here (or maybe a different error function should be used in `LAPACK.trsyl!`). Please open an issue on github about this!
---
### Author:  [@rdeits](https://discourse.julialang.org/u/rdeits)
#### Post date: [July 16, 2021, 2:21pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/6 "2021-07-16T14:21:25Z")
What Julia version are you using? In Julia 1.6.1 your exact example appears to work correctly:
```julia
julia> lyap(Matrix(B'),A)
16×16 Matrix{Float64}:
284.002 -283.488 234.109
...
```
```julia
julia> X = lyap(Matrix(B'), A);
julia> isapprox(B' * X + X * B + A, zeros(size(A)), atol=1e-8)
true
```
---
### Author:  [@gbaraldi](https://discourse.julialang.org/u/gbaraldi)
#### Post date: [July 16, 2021, 2:27pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/7 "2021-07-16T14:27:47Z")
Thats weird, for me it fails on rosetta
```julia
julia> versioninfo()
Julia Version 1.6.1
Commit 6aaedecc44 (2021-04-23 05:59 UTC)
Platform Info:
OS: macOS (x86_64-apple-darwin18.7.0)
CPU: Apple M1
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-11.0.1 (ORCJIT, westmere)
Environment:
JULIA_NUM_THREADS = 4
```
And on native
```julia
versioninfo()
Julia Version 1.8.0-DEV.138
Commit 018977209b* (2021-07-06 11:28 UTC)
Platform Info:
OS: macOS (arm64-apple-darwin20.5.0)
CPU: Apple M1
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-12.0.0 (ORCJIT, cyclone)
Environment:
JULIA_NUM_THREADS = 4
```
---
### Author:  [@Sukera](https://discourse.julialang.org/u/Sukera)
#### Post date: [July 16, 2021, 2:35pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/8 "2021-07-16T14:35:12Z")
It definitely also fails for me on
```julia
julia> versioninfo()
Julia Version 1.7.0-DEV.1072
Commit 364660c5fd (2021-05-07 06:23 UTC)
Platform Info:
OS: Linux (x86_64-linux-gnu)
CPU: Intel(R) Core(TM) i7-6600U CPU @ 2.60GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-11.0.1 (ORCJIT, skylake)
Environment:
JULIA_PKG_SERVER =
JULIA_NUM_THREADS = 4
```
---
### Author:  [@ylish](https://discourse.julialang.org/u/ylish)
#### Post date: [July 16, 2021, 8:19pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/9 "2021-07-16T20:19:38Z")
> [@zdenek\_hurak](#):
>
> `using MatrixEquations`
Thank you very much! I have marked this as the solution as it might help others as well looking to solve these equations.
---
### Author:  [@ylish](https://discourse.julialang.org/u/ylish)
#### Post date: [July 16, 2021, 8:20pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/10 "2021-07-16T20:20:42Z")
Thank you for the help! Were you asking me to open an issue on github? I haven’t done so before thus could you let me know what I should do?
---
### Author:  [@ylish](https://discourse.julialang.org/u/ylish)
#### Post date: [July 16, 2021, 8:21pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/11 "2021-07-16T20:21:22Z")
Thank you! This makes sense!
---
### Author:  [@gbaraldi](https://discourse.julialang.org/u/gbaraldi)
#### Post date: [July 16, 2021, 8:34pm UTC](https://discourse.julialang.org/t/problem-with-lyap-q-r/64745/12 "2021-07-16T20:34:48Z")
Not sure if you want to open this one but go here [Issues · JuliaLang/julia · GitHub](https://github.com/JuliaLang/julia/issues) click new issue. Also give a read to [julia/CONTRIBUTING.md at e1aeb8a95ede8212ea09bdb49bdd805f66dfb9d5 · JuliaLang/julia · GitHub](https://github.com/JuliaLang/julia/blob/e1aeb8a95ede8212ea09bdb49bdd805f66dfb9d5/CONTRIBUTING.md) so that your issue can help the developers as much as possible to reproduce and then fix the bug.