# Matrix equation solution via GenericLinearAlgebra with BigFloat not working

**URL:** <https://discourse.julialang.org/t/matrix-equation-solution-via-genericlinearalgebra-with-bigfloat-not-working/119662>\
**Category:** Numerics\
**Tags:** question\
**Created:** [September 21, 2024, 3:17am UTC](https://discourse.julialang.org/t/matrix-equation-solution-via-genericlinearalgebra-with-bigfloat-not-working/119662 "2024-09-21T03:17:07Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![thedeyan](https://avatars.discourse-cdn.com/v4/letter/t/6bbea6/32.png) [@thedeyan](https://discourse.julialang.org/u/thedeyan)\
**Post date:** [September 21, 2024, 3:17am UTC](https://discourse.julialang.org/t/matrix-equation-solution-via-genericlinearalgebra-with-bigfloat-not-working/119662/1 "2024-09-21T03:17:08Z")

</div>

I am trying to solve a system of linear equations:  
`A * x = B`  
where `A` and `B` are real symmetric positive definite matrices with type `BigFloat`.

I am trying to do the following:

```julia
using GenericLinearAlgebra
using LinearSolve

n = 100

A = big.(randn(n, n));
A = A * A';

B = big.(randn(n, n));
B = B * B';

c = big.(randn(n));

prob = LinearProblem(A, B);
solve(prob)

```

which yields the error

```julia
MethodError: no method matching ldiv!(::Vector{BigFloat}, ::LinearAlgebra.LU{BigFloat, Matrix{BigFloat}, Vector{Int64}}, ::Matrix{BigFloat})

```

If I use a vector instead of a matrix, i.e.

```julia
prob = LinearProblem(A, c);
solve(prob)

```

then it produces a result.

What is the workaround here to make it work for matrices? I can see in the `GenericLinearAlgebra.jl` package there are functions for matrix equations, but I am not sure how to access gthem.

---

<div class="post-metadata">

**Author:** ![thedeyan](https://avatars.discourse-cdn.com/v4/letter/t/6bbea6/32.png) [@thedeyan](https://discourse.julialang.org/u/thedeyan)\
**Post date:** [September 21, 2024, 3:45am UTC](https://discourse.julialang.org/t/matrix-equation-solution-via-genericlinearalgebra-with-bigfloat-not-working/119662/2 "2024-09-21T03:45:03Z")

</div>

Coming back to answer my own question, it turns out that the linear solution is done by

```julia
\(A, B)

```

for a pair of matrices.