# No method matching isless(::Array{Float64,2}, ::Array{Float64,2})

**URL:** https://discourse.julialang.org/t/no-method-matching-isless-array-float64-2-array-float64-2/48086
**Category:** General Usage
**Tags:** question, package, optim, zygote
**Created:** [October 10, 2020, 2:37am UTC](https://discourse.julialang.org/t/no-method-matching-isless-array-float64-2-array-float64-2/48086 "2020-10-10T02:37:42Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![F-YF](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/f-yf/32/17363_2.png) [@F-YF](https://discourse.julialang.org/u/F-YF)
#### Post date: [October 10, 2020, 2:37am UTC](https://discourse.julialang.org/t/no-method-matching-isless-array-float64-2-array-float64-2/48086/1 "2020-10-10T02:37:42Z")

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When I call the Optimizer.jl package, the following error occurs:

> MethodError: no method matching isless(::Array{Float64,2}, ::Array{Float64,2})

Because of the size of my program, I can’t construct an example to replicate this error. I try to provide the parameter characteristics of the function I call.

> optimize(f,g!,I\_A,LBFGS())

> MethodError: no method matching isless(::Array{Float64,2}, ::Array{Float64,2})  
> Closest candidates are:  
> isless(!Matched::Missing, ::Any) at missing.jl:87  
> isless(::Any, !Matched::Missing) at missing.jl:88  
> .  
> Stacktrace:  
> [1] \<(::Array{Float64,2}, ::Array{Float64,2}) at .\operators.jl:277  
> [2] \>(::Array{Float64,2}, ::Array{Float64,2}) at .\operators.jl:303  
> [3] maxdiff(::VectorOfArray{Float64,3,Array{Array{Float64,2},1}}, ::VectorOfArray{Float64,3,Array{Array{Float64,2},1}}) at C:\Users\Fu Yangfeng.julia\packages\Optim\auGGa\src\utilities\maxdiff.jl:5  
> [4] x\_abschange at C:\Users\Fu Yangfeng.julia\packages\Optim\auGGa\src\utilities\assess\_convergence.jl:7 [inlined]  
> [5] x\_abschange at C:\Users\Fu Yangfeng.julia\packages\Optim\auGGa\src\utilities\assess\_convergence.jl:6 [inlined]  
> [6] optimize(::OnceDifferentiable{Float64,VectorOfArray{Float64,3,Array{Array{Float64,2},1}},VectorOfArray{Float64,3,Array{Array{Float64,2},1}}}, ::VectorOfArray{Float64,3,Array{Array{Float64,2},1}}, ::LBFGS{Nothing,LineSearches.InitialStatic{Float64},LineSearches.HagerZhang{Float64,Base.RefValue{Bool}},Optim.var"#15#17"}, ::Optim.Options{Float64,Nothing}, ::Optim.LBFGSState{VectorOfArray{Float64,3,Array{Array{Float64,2},1}},Array{VectorOfArray{Float64,3,Array{Array{Float64,2},1}},1},Array{VectorOfArray{Float64,3,Array{Array{Float64,2},1}},1},Float64,VectorOfArray{Float64,3,Array{Array{Float64,2},1}}}) at C:\Users\Fu Yangfeng.julia\packages\Optim\auGGa\src\multivariate\optimize\optimize.jl:103  
> [7] optimize(::OnceDifferentiable{Float64,VectorOfArray{Float64,3,Array{Array{Float64,2},1}},VectorOfArray{Float64,3,Array{Array{Float64,2},1}}}, ::VectorOfArray{Float64,3,Array{Array{Float64,2},1}}, ::LBFGS{Nothing,LineSearches.InitialStatic{Float64},LineSearches.HagerZhang{Float64,Base.RefValue{Bool}},Optim.var"#15#17"}, ::Optim.Options{Float64,Nothing}) at C:\Users\Fu Yangfeng.julia\packages\Optim\auGGa\src\multivariate\optimize\optimize.jl:33  
> [8] optimize(::Function, ::Function, ::VectorOfArray{Float64,3,Array{Array{Float64,2},1}}, ::LBFGS{Nothing,LineSearches.InitialStatic{Float64},LineSearches.HagerZhang{Float64,Base.RefValue{Bool}},Optim.var"#15#17"}, ::Optim.Options{Float64,Nothing}; inplace::Bool, autodiff::Symbol) at C:\Users\Fu Yangfeng.julia\packages\Optim\auGGa\src\multivariate\optimize\interface.jl:155  
> [9] optimize(::Function, ::Function, ::VectorOfArray{Float64,3,Array{Array{Float64,2},1}}, ::LBFGS{Nothing,LineSearches.InitialStatic{Float64},LineSearches.HagerZhang{Float64,Base.RefValue{Bool}},Optim.var"#15#17"}, ::Optim.Options{Float64,Nothing}) at C:\Users\Fu Yangfeng.julia\packages\Optim\auGGa\src\multivariate\optimize\interface.jl:153 (repeats 2 times)  
> [10] top-level scope at In[19]:1  
> [11] include\_string(::Function, ::Module, ::String, ::String) at .\loading.jl:1091  
> [12] execute\_code(::String, ::String) at C:\Users\Fu Yangfeng.julia\packages\IJulia\rWZ9e\src\execute\_request.jl:27  
> [13] execute\_request(::ZMQ.Socket, ::IJulia.Msg) at C:\Users\Fu Yangfeng.julia\packages\IJulia\rWZ9e\src\execute\_request.jl:86  
> [14] #invokelatest#1 at .\essentials.jl:710 [inlined]  
> [15] invokelatest at .\essentials.jl:709 [inlined]  
> [16] eventloop(::ZMQ.Socket) at C:\Users\Fu Yangfeng.julia\packages\IJulia\rWZ9e\src\eventloop.jl:8  
> [17] (::IJulia.var"#15#18")() at .\task.jl:356

The type of I\_A is Array{Array{Float64,2},1}. I guess that one step in Optimal. jl compares the size of elements in A, but the isless() does not support the comparison of two matrices. What should I do?

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### Author: ![CameronBieganek](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/cameronbieganek/32/6915_2.png) [@CameronBieganek](https://discourse.julialang.org/u/CameronBieganek)
#### Post date: [October 10, 2020, 3:12am UTC](https://discourse.julialang.org/t/no-method-matching-isless-array-float64-2-array-float64-2/48086/3 "2020-10-10T03:12:45Z")

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Can you give us the code for `f` and `g!`? There could be an issue in the way that you’ve defined those functions.