From 9439179a0a1863aba5ff4c8b4b5dea8ec3940c8d Mon Sep 17 00:00:00 2001
From: Hugo <hugovk@users.noreply.github.com>
Date: Wed, 2 Oct 2019 18:11:35 +0300
Subject: [PATCH] Reinstate and simplify parallel auto-detection

---
 setup.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/setup.py b/setup.py
index c3e0dfc9fe1..c72e029665e 100755
--- a/setup.py
+++ b/setup.py
@@ -326,6 +326,15 @@ def finalize_options(self):
         if self.debug:
             global DEBUG
             DEBUG = True
+        if not self.parallel:
+            # If --parallel (or -j) wasn't specified, we want to reproduce the same
+            # behavior as before, that is, auto-detect the number of jobs.
+            try:
+                self.parallel = int(
+                    os.environ.get("MAX_CONCURRENCY", min(4, os.cpu_count()))
+                )
+            except TypeError:
+                self.parallel = None
         for x in self.feature:
             if getattr(self, "disable_%s" % x):
                 setattr(self.feature, x, False)