[R] How to get the same result for GA optimization?

[Michael Dewey]

Dear Daniel

As far as I can see you have re-generated the data before calling ga() 
so the data is not just a permutation of the first set.

Michael

On 07/05/2025 15:36, Daniel Lobo wrote:
> I am using *Genetic Algorithm* to maximize some function which use data.
> 
> I use GA package in R for this (
> https://cran.r-project.org/web/packages/GA/index.html)
> 
> Below is my code
> 
> library(GA)
> set.seed(1)
> Dat = data.frame(rnorm(1000), matrix(rnorm(1000 * 30), nc = 30))
> 
> Fitness_Fn = function(x) {
>      return(cor(Dat[, 1], as.matrix(Dat[, -1]) %*% matrix(x, nc = 1))[1,1])
> }
> 
> ga(type = 'real-valued', fitness = Fitness_Fn, seed = 1, lower =
> rep(0, 30), upper = rep(1, 30), elitism = 10, popSize = 200, maxiter =
> 1, pcrossover = 0.9, pmutation = 0.9, run = 1)
> 
> However now I alter the columns of my data and rerun the GA
> 
> Dat = Dat[, c(1, 1 + sample(1:30, 30, replace = F))]
> Fitness_Fn = function(x) {
>      return(cor(Dat[, 1], as.matrix(Dat[, -1]) %*% matrix(x, nc = 1))[1,1])
> }
> 
> ga(type = 'real-valued', fitness = Fitness_Fn, seed = 1, lower =
> rep(0, 30), upper = rep(1, 30), elitism = 10, popSize = 200, maxiter =
> 1, pcrossover = 0.9, pmutation = 0.9, run = 1)
> 
> Surprisingly, I get different result from above 2 implementations.
> 
> In first case, I get
> 
> GA | iter = 1 | Mean = 0.01534124 | Best = 0.04351926
> 
> In second case,
> 
> GA | iter = 1 | Mean = 0.01705027 | Best = 0.04454167
> 
> I have fixed the random number generation using seed = 1 in the ga() function,
> So I am expecting I would get exactly same result.
> 
> Could you please help identify the issue here? I want to get exactly same
> result irrespective of the order of the columns of dat for above function.
> 
> Thanks for your time.
> 
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> 
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-- 
Michael Dewey