From 0a193a656a124bc0901c5cfae647b12774924567 Mon Sep 17 00:00:00 2001
From: Lyndon White <lyndon.white@invenialabs.co.uk>
Date: Sat, 13 Apr 2019 14:11:08 +0100
Subject: [PATCH] sizehint back down

---
 base/reduce.jl | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/base/reduce.jl b/base/reduce.jl
index cb4c1e5a497cd..0295968ce58e6 100644
--- a/base/reduce.jl
+++ b/base/reduce.jl
@@ -383,10 +383,15 @@ function reduce(::typeof(vcat), xs, T::Type{<:AbstractVector}, isize)
 
     ret = copy(x1)  # this is **Not** going to work for StaticArrays
 
+    hinted_size = 0
     if !(isize isa SizeUnknown)
         # Assume first element has representitive size, unless that would make this too large
-        SIZEHINT_CAP = 10^6
-        sizehint!(ret, min(SIZEHINT_CAP, length(xs)*length(x1)))
+        SIZEHINT_CAP = 10^5
+        expected_size = length(xs)*length(x1)
+        if expected_size < SIZEHINT_CAP
+            hinted_size = expected_size
+            sizehint!(ret, hinted_size)
+        end
     end
 
     x_state = iterate(xs, state)
@@ -395,6 +400,11 @@ function reduce(::typeof(vcat), xs, T::Type{<:AbstractVector}, isize)
         append!(ret, x)
         x_state = iterate(xs, state)
     end
+
+    if length(ret) < hinted_size/2  # it is only allowable to be at most 2x to much memory
+        sizehint!(ret, length(ret))
+    end
+
     return ret
 end