Introductory time series with torch blog example is extremely slow for multi step prediction

[jzicker]

the section on multi step prediction is very, very slow on mac os. Any tips or tricks to speed it up?

n_forecast <- 2 * 24 * 7

test_preds <- [vector](https://rdrr.io/r/base/vector.html)(mode = "list", length = [length](https://rdrr.io/r/base/length.html)(test_dl))

i <- 1

coro::loop(for (b in test_dl) {
  
  input <- b$x
  output <- net(input$to(device = device))
  preds <- [as.numeric](https://rdrr.io/r/base/numeric.html)(output)
  
  for(j in 2:n_forecast) {
    input <- torch_cat([list](https://rdrr.io/r/base/list.html)(input[ , 2:[length](https://rdrr.io/r/base/length.html)(input), ], output$view([c](https://rdrr.io/r/base/c.html)(1, 1, 1))), dim = 2)
    output <- net(input$to(device = device))
    preds <- [c](https://rdrr.io/r/base/c.html)(preds, [as.numeric](https://rdrr.io/r/base/numeric.html)(output))
  }
  
  test_preds[[i]] <- preds
  i <<- i + 1
  
})