From 01326d69cfd95600d1908df67424c245fa8df915 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 16 Jun 2019 18:47:36 +0530
Subject: [PATCH] py3: Use os.cpu_count()

---
 src/calibre/__init__.py | 43 ++++++++++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/src/calibre/__init__.py b/src/calibre/__init__.py
index 90dc052c81..9a232564be 100644
--- a/src/calibre/__init__.py
+++ b/src/calibre/__init__.py
@@ -18,7 +18,7 @@ except EnvironmentError:
 
 from calibre.constants import (iswindows, isosx, islinux, isfrozen,
         isbsd, preferred_encoding, __appname__, __version__, __author__,
-        win32event, win32api, winerror, fcntl,
+        win32event, win32api, winerror, fcntl, ispy3,
         filesystem_encoding, plugins, config_dir)
 from calibre.startup import winutil, winutilerror
 from calibre.utils.icu import safe_chr
@@ -454,23 +454,30 @@ class CurrentDir(object):
 _ncpus = None
 
 
-def detect_ncpus():
-    """Detects the number of effective CPUs in the system"""
-    global _ncpus
-    if _ncpus is None:
-        if iswindows:
-            import win32api
-            ans = win32api.GetSystemInfo()[5]
-        else:
-            import multiprocessing
-            ans = -1
-            try:
-                ans = multiprocessing.cpu_count()
-            except Exception:
-                from PyQt5.Qt import QThread
-                ans = QThread.idealThreadCount()
-        _ncpus = max(1, ans)
-    return _ncpus
+if ispy3:
+    def detect_ncpus():
+        global _ncpus
+        if _ncpus is None:
+            _ncpus = max(1, os.cpu_count() or 1)
+        return _ncpus
+else:
+    def detect_ncpus():
+        """Detects the number of effective CPUs in the system"""
+        global _ncpus
+        if _ncpus is None:
+            if iswindows:
+                import win32api
+                ans = win32api.GetSystemInfo()[5]
+            else:
+                import multiprocessing
+                ans = -1
+                try:
+                    ans = multiprocessing.cpu_count()
+                except Exception:
+                    from PyQt5.Qt import QThread
+                    ans = QThread.idealThreadCount()
+            _ncpus = max(1, ans)
+        return _ncpus
 
 
 relpath = os.path.relpath