Replace vec_repeat() with vec_rep() and vec_rep_each() (#1131)

* speed up `vec_repeat()`

* replace `vec_repeat()`

* Refactor `expand_grid()`

Author: mgirlich

NEWS.md

@@ -1,5 +1,8 @@
 # tidyr (development version)
 
+* `expand_grid()` is now about twice as fast and `pivot_wider()` is a bit faster
+  (@mgirlich, #1130).
+
 * `unnest()` is now much faster (@mgirlich, @DavisVaughan, #1127).
 
 * `unnest()` no longer allows unnesting a list-col containing a mix of vector

R/expand.R

@@ -167,10 +167,10 @@ expand_grid <- function(..., .name_repair = "check_unique") {
   if (n == 0) {
     out <- map(dots, vec_slice, integer())
   } else {
-    each <- n / cumprod(ns)
-    times <- n / each / ns
-
-    out <- pmap(list(x = dots, each = each, times = times), vec_repeat)
+    times <- n / cumprod(ns)
+    out <- map2(dots, times, vec_rep_each)
+    times <- n / times / ns
+    out <- map2(out, times, vec_rep)
   }
   out <- as_tibble(out, .name_repair = .name_repair)
 

R/pivot-wide.R

@@ -261,7 +261,7 @@ pivot_wider_spec <- function(data,
     } else {
       stopifnot(vec_size(fill) == 1)
       fill <- vec_cast(fill, val)
-      out <- vec_repeat(fill, nrow * ncol)
+      out <- vec_rep_each(fill, nrow * ncol)
     }
     vec_slice(out, val_id$row + nrow * (val_id$col - 1L)) <- val
 
@@ -308,11 +308,11 @@ build_wider_spec <- function(data,
   if (length(values_from) == 1) {
     out$.value <- names(values_from)
   } else {
-    out <- vec_repeat(out, times = vec_size(values_from))
-    out$.value <- vec_repeat(names(values_from), each = vec_size(row_ids))
+    out <- vec_rep(out, vec_size(values_from))
+    out$.value <- vec_rep_each(names(values_from), vec_size(row_ids))
     out$.name <- paste0(out$.value, names_sep, out$.name)
 
-    row_ids <- vec_repeat(row_ids, times = vec_size(values_from))
+    row_ids <- vec_rep(row_ids, vec_size(values_from))
   }
 
   out <- vec_cbind(out, as_tibble(row_ids), .name_repair = "minimal")

R/utils.R

@@ -114,16 +114,6 @@ tidyr_col_modify <- function(data, cols) {
   data
 }
 
-# Own copy since it might disappear from vctrs since it
-# isn't well thought out
-vec_repeat <- function(x, each = 1L, times = 1L) {
-  vec_assert(each, size = 1L)
-  vec_assert(times, size = 1L)
-
-  idx <- rep(vec_seq_along(x), times = times, each = each)
-  vec_slice(x, idx)
-}
-
 check_present <- function(x) {
   arg <- ensym(x)
   if (missing(x)) {