# Multiplication of matrix expression and variables leads to stack overflow and matmul error
**URL:** https://discourse.julialang.org/t/multiplication-of-matrix-expression-and-variables-leads-to-stack-overflow-and-matmul-error/111760
**Category:** Optimization (Mathematical)
**Tags:** jump, optimization, stackoverflow, nonlinear
**Created:** [March 18, 2024, 10:31am UTC](https://discourse.julialang.org/t/multiplication-of-matrix-expression-and-variables-leads-to-stack-overflow-and-matmul-error/111760 "2024-03-18T10:31:07Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Rahul\_Narwar](https://discourse.julialang.org/u/Rahul_Narwar)
#### Post date: [March 18, 2024, 10:31am UTC](https://discourse.julialang.org/t/multiplication-of-matrix-expression-and-variables-leads-to-stack-overflow-and-matmul-error/111760/1 "2024-03-18T10:31:07Z")
I have an optimal orbital transfer problem:
```julia
h = 2
n = 6
m = 3
model = Model(NLopt.Optimizer)
set_optimizer_attribute(model, "algorithm", :AUGLAG)
local_optimizer = NLopt.Opt(:LD_LBFGS, n*(h+1) + m*h)
local_optimizer.xtol_rel = 1e-4
set_optimizer_attribute(model, "local_optimizer", local_optimizer)
@variables model begin
X[1:6, 1:h+1]
U[1:3, 1:h]
27000.0 <= T[1:h]
end
```
Trying to multiply an expression matrix
```julia
B
6×3 Matrix{Any}:
((2 X[1,1]²) / (X[1,1] * sqrt(3.986004415e14 / X[1,1]))) * (X[2,1] * sin(X[6,1])) … 0
(1.0 / (X[1,1] * sqrt(3.986004415e14 / X[1,1]))) * ((X[1,1] * (-X[2,1]² + 1)) * sin(X[6,1])) 0
0 (((X[1,1] * (-X[2,1]² + 1)) / (1.0 + (X[2,1] * cos(X[6,1])))) * cos(X[6,1] + X[4,1])) / (X[1,1] * sqrt(3.986004415e14 / X[1,1]))
(-(X[1,1] * (-X[2,1]² + 1)) * cos(X[6,1])) / (X[2,1] * (X[1,1] * sqrt(3.986004415e14 / X[1,1]))) -((((X[1,1] * (-X[2,1]² + 1)) / (1.0 + (X[2,1] * cos(X[6,1])))) * sin(X[6,1] + X[4,1])) * cos(X[3,1])) / ((X[1,1] * sqrt(3.986004415e14 / X[1,1])) * sin(X[3,1]))
0 (((X[1,1] * (-X[2,1]² + 1)) / (1.0 + (X[2,1] * cos(X[6,1])))) * sin(X[6,1] + X[4,1])) / ((X[1,1] * sqrt(3.986004415e14 / X[1,1])) * sin(X[3,1]))
((X[1,1] * (-X[2,1]² + 1)) * cos(X[6,1])) / (X[2,1] * (X[1,1] * sqrt(3.986004415e14 / X[1,1]))) … 0
```
with
```julia
U[:, i] = JuMP.VariableRef[U[1,1], U[2,1], U[3,1]]
```
by executing:
```julia
B1 = B(X[:,1])
B1*U[:,1]
```
Results in the following stack overflow error:
```julia
operate(::typeof(*), ::Matrix{Any}, ::Vector{JuMP.VariableRef})@LinearAlgebra.jl:403
mul(::Matrix{Any}, ::Vector{JuMP.VariableRef})@shortcuts.jl:58
*(::Matrix{Any}, ::Vector{JuMP.VariableRef})@dispatch.jl:360
[Repeated 100 times]
operate(::typeof(*), ::Matrix{Any}, ::Vector{JuMP.VariableRef})@LinearAlgebra.jl:403
mul(::Matrix{Any}, ::Vector{JuMP.VariableRef})@shortcuts.jl:58
*(::Matrix{Any}, ::Vector{JuMP.VariableRef})@dispatch.jl:360
```
Whereas doing:
```julia
B1*U[:,:]
```
Gives the correct result, a 6x2 matrix.
Help in understanding and resolving the problem is appreciated!
---
### Author:  [@miles.lubin](https://discourse.julialang.org/u/miles.lubin)
#### Post date: [March 18, 2024, 11:13am UTC](https://discourse.julialang.org/t/multiplication-of-matrix-expression-and-variables-leads-to-stack-overflow-and-matmul-error/111760/2 "2024-03-18T11:13:48Z")
Please link when cross-posting: [Multiplication of matrix expression and variables leads to stack overflow and matmul error · Issue #3714 · jump-dev/JuMP.jl · GitHub](https://github.com/jump-dev/JuMP.jl/issues/3714)
---
### Author:  [@Rahul\_Narwar](https://discourse.julialang.org/u/Rahul_Narwar)
#### Post date: [March 18, 2024, 12:00pm UTC](https://discourse.julialang.org/t/multiplication-of-matrix-expression-and-variables-leads-to-stack-overflow-and-matmul-error/111760/3 "2024-03-18T12:00:10Z")
The issue was resolved by upgrading the packages to the latest release.