# Promote operation; report this

I have the following code in which a constraint is giving a “promote operation error”:

``````using JuMP
using MosekTools
K = 3
N = 2
penalties = [1.0, 3.9, 8.7]
function fac1(r::Number, i::Number, l::Number)
fac1 = 1.0
for m in 0:r-1
fac1 *= (i-m)*(l-m)
end
return fac1
end

function fac2(r::Number, i::Number, l::Number, tau::Float64)
return tau ^ (i + l - 2r + 1)/(i + l - 2r + 1)
end

function Q_r(i::Number, l::Number, r::Number, tau::Float64)
if i >= r && l >= r
return 2 * fac1(r, i, l) * fac2(r, i, l, tau)
else
return 0.0
end
end

function Q(i::Number, l::Number, tau::Number)
elem = 0
for r in 0:N
elem += penalties[r + 1] * Q_r(i, l, r, tau)
end
return elem
end

# discrete segment starting times

function Q_mat()
mat = Array{Float64, 3}(undef, K, N+1, N+1)
for k in 0:K-1
for i in 1:N+1
for j in 1:N+1
mat[k+1, i, j] = Q(i, j, convert(Float64, k))
end
end
return mat
end
end

function A_tau(r::Number, n::Number, tau::Float64)
fac = 1
for m in 1:r
fac *= (n - (m - 1))
end
if n >= r
return fac * tau ^ (n - r)
else
return 0.0
end
end

function A_tau_mat(tau::Float64)
mat = Array{Float64, 2}(undef, N+1, N+1)
for i in 1:N+1
for j in 1:N+1
mat[i, j] = A_tau(i, j, tau)
end
end
return mat
end

function A_0(r::Number, n::Number)
if r == n
fac = 1
for m in 1:r
fac *= r - (m - 1)
end
return fac
else
return 0.0
end
end

m = Model(optimizer_with_attributes(Mosek.Optimizer, "QUIET" => false, "INTPNT_CO_TOL_DFEAS" => 1e-7))

@variable(m, A[i=1:K+1,j=1:K,k=1:N+1,l=1:N+1])
@variable(m, p[i=1:K+1,j=1:N+1])

# constraint difference might be a small fractional difference.
# assuming that time difference is 1 second starting from 0.
for i in 1:K
@constraint(m, -A_tau_mat(convert(Float64, i-1)) * p[i] .+ A_tau_mat(convert(Float64, i-1)) * p[i+1] == [0.0, 0.0, 0.0])
end

for i in 1:K+1
@constraint(m, A_tau_mat(convert(Float64, i-1)) * p[i] == [1.0 12.0 13.0])
end
@constraint(m, A_tau_mat(convert(Float64, K+1)) * p[K+1] == [1.0 2.0 0.0])

@objective(m, Min, sum(p[i]' * Q_mat()[i] * p[i] for i in 1:K+1))

optimize!(m)
println("p value is ", value.(p))
println(A_tau_mat(0.0), A_tau_mat(1.0), A_tau_mat(2.0))

``````
``````ERROR: LoadError: `promote_operation(-, Array{GenericAffExpr{Float64,VariableRef},2}, Array{Float64,1})` not implemented yet, please report this.
Stacktrace:
 error(::String) at ./error.jl:33
 promote_operation(::Function, ::Type{Array{GenericAffExpr{Float64,VariableRef},2}}, ::Type{Array{Float64,1}}) at /Users/prikshetsharma/.julia/packages/MutableArithmetics/0tlz5/src/interface.jl:16
 promote_operation(::typeof(MutableArithmetics.sub_mul), ::Type{Array{GenericAffExpr{Float64,VariableRef},2}}, ::Type{Array{Float64,1}}) at /Users/prikshetsharma/.julia/packages/MutableArithmetics/0tlz5/src/shortcuts.jl:56
 mutability(::Type{T} where T, ::Function, ::Type{T} where T, ::Type{T} where T) at /Users/prikshetsharma/.julia/packages/MutableArithmetics/0tlz5/src/interface.jl:132
 mutability(::Array{GenericAffExpr{Float64,VariableRef},2}, ::Function, ::Array{GenericAffExpr{Float64,VariableRef},2}, ::Array{Float64,1}) at /Users/prikshetsharma/.julia/packages/MutableArithmetics/0tlz5/src/interface.jl:138
 operate!(::typeof(MutableArithmetics.sub_mul), ::Array{GenericAffExpr{Float64,VariableRef},2}, ::Array{Float64,1}) at /Users/prikshetsharma/.julia/packages/MutableArithmetics/0tlz5/src/rewrite.jl:70
 macro expansion at /Users/prikshetsharma/.julia/packages/MutableArithmetics/0tlz5/src/rewrite.jl:227 [inlined]
 macro expansion at /Users/prikshetsharma/.julia/packages/JuMP/qhoVb/src/macros.jl:440 [inlined]
 top-level scope at /Users/prikshetsharma/Documents/clotorch/src/clotorch/flight/trajectory.jl:92
 include(::Function, ::Module, ::String) at ./Base.jl:380
 include(::Module, ::String) at ./Base.jl:368
 exec_options(::Base.JLOptions) at ./client.jl:296
 _start() at ./client.jl:506
in expression starting at /Users/prikshetsharma/Documents/clotorch/src/clotorch/flight/trajectory.jl:91
``````

The error is in the line:

``````@constraint(m, -A_tau_mat(convert(Float64, i-1)) * p[i] .+ A_tau_mat(convert(Float64, i-1)) * p[i+1] == [0.0, 0.0, 0.0])
``````

This error disappears when == is replaced with .==. Why is that and how to fix this error?

This error disappears when == is replaced with .==

In your constraint, the left-hand side is a vector; so is the right-hand side.

To compare two vectors, and as stated in the documentation, you should use the broadcast notation `.==` and not the regular `==`.

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