# How to optimize struct for speed?

**URL:** <https://discourse.julialang.org/t/how-to-optimize-struct-for-speed/108518>\
**Category:** Performance\
**Tags:** struct\
**Created:** [January 8, 2024, 1:49pm UTC](https://discourse.julialang.org/t/how-to-optimize-struct-for-speed/108518 "2024-01-08T13:49:25Z")\
**Posts on this page:** 1\
**Showing post:** 5

<div class="post-metadata">

**Author:** ![rocco\_sprmnt21](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rocco_sprmnt21/32/20127_2.png) [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)\
**Post date:** [January 9, 2024, 8:53am UTC](https://discourse.julialang.org/t/how-to-optimize-struct-for-speed/108518/5 "2024-01-09T08:53:05Z")

</div>

Trying to understand why the solution proposed by @Dan using this function  
[Tables.columntype(sch, :Close)](https://discourse.julialang.org/t/how-to-get-type-of-a-column-using-tables-schema-from-tables-jl/108432/5) is much faster than the others, I came to narrow down the reason for the difference in the use of structures in a similar way (if I understand correctly) to what was discussed here.

```julia
julia> using CSV, Tables, DataFrames, Dates, TSFrames

julia> df=CSV.read("table.txt",DataFrame,delim=' ', ignorerepeated=true);    

julia> tsdf=TSFrame(df);

julia> sch = Tables.schema(tsdf)
Tables.Schema:
 :Index Date
 :Open Float64
 :High Float64
 :Low Float64
 :Close Float64
 :Volume Float64

julia> using BenchmarkTools

julia> n,t= sch.names,sch.types
((:Index, :Open, :High, :Low, :Close, :Volume), (Date, Float64, Float64, Float64, Float64, Float64))

julia> @btime t[findfirst(==(:Close),$n)]
  191.888 ns (0 allocations: 0 bytes)
Float64

julia> n,t= sch.names,Tuple{sch.types...}
((:Index, :Open, :High, :Low, :Close, :Volume), Tuple{Date, Vararg{Float64, 5}})

julia> @btime fieldtype(t, findfirst(==(:Close),$n))
  10.010 ns (0 allocations: 0 bytes)
Float64

julia> @btime Tables.columntype(sch, :Close)
  12.813 ns (0 allocations: 0 bytes)
Float64

```

What I couldn’t delve into(\*) is why the `fieldtype(Tuple{t...},i)` function is so much faster than `getindex(t,i)`.

(\*) ```  
julia\> @edit fieldtype(t, findfirst(==(:Close),n))  
ERROR: could not determine location of method definition  
Stacktrace:

```julia

```

---

_[View the full topic](https://discourse.julialang.org/t/how-to-optimize-struct-for-speed/108518)._