Use a random grid for a one point design

NEWS.md

@@ -4,7 +4,7 @@
 
 * The package will now log a backtrace for errors and warnings that occur during tuning. When a tuning process encounters issues, see the new `trace` column in the `collect_notes(.Last.tune.result)` output to find precisely where the error occurred (#873).
 
-* When automatic grids are used, `dials::grid_space_filling()` is now used (instead of `dials::grid_latin_hypercube()`). Overall, the new function produces optimized designs (not depending on random numbers). When using Bayesian models, we will use a Latin Hypercube since we produce 5,000 candidates, which is too slow to do with pre-optimized designs. 
+* When automatic grids are used, `dials::grid_space_filling()` is now used (instead of `dials::grid_latin_hypercube()`). There is an exception: when `grid = 1`, `dials::grid_random()` is used to avoid warnings. Overall, the new function produces optimized designs (not depending on random numbers). When using Bayesian models, we will use a Latin Hypercube since we produce 5,000 candidates, which is too slow to do with pre-optimized designs. (#962) 
 
 # tune 1.2.1
 

R/tune_bayes.R

@@ -531,7 +531,12 @@ create_initial_set <- function(param, n = NULL, checks) {
   if (any(checks == "bayes")) {
     check_bayes_initial_size(nrow(param), n)
   }
-  dials::grid_space_filling(param, size = n)
+  if (n == 1) {
+    res <- dials::grid_random(param, size = n)
+  } else {
+    res <- dials::grid_space_filling(param, size = n)
+  }
+  res
 }
 
 check_iter <- function(iter, call) {

tests/testthat/test-bayes.R

@@ -611,3 +611,19 @@ test_that("tune_bayes() output for `iter` edge cases (#721)", {
     tune_bayes(wf, boots, iter = NULL)
   )
 })
+
+test_that("1-point grid (#962)", {
+  skip_if_not_installed("dials", minimum_version = "1.3.0")
+
+  expect_silent({
+    set.seed(1)
+    grid <- tune:::create_initial_set(
+      dials::parameters(dials::penalty(), dials::deg_free()),
+      n = 1,
+      checks = "none"
+    )
+  })
+  expect_equal(nrow(grid), 1L)
+})
+
+