refactor: move spack.util.multiproc to llnl.util.multiproc

- multiproc doesn't depend on Spack
- llnl.util.lock test uses it, but shouldn't use parts of Spack.

lib/spack/llnl/util/multiproc.py

@@ -0,0 +1,96 @@
+##############################################################################
+# Copyright (c) 2013-2018, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/spack/spack
+# Please also see the NOTICE and LICENSE files for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+"""
+This implements a parallel map operation but it can accept more values
+than multiprocessing.Pool.apply() can.  For example, apply() will fail
+to pickle functions if they're passed indirectly as parameters.
+"""
+from multiprocessing import Process, Pipe, Semaphore, Value
+
+__all__ = ['spawn', 'parmap', 'Barrier']
+
+
+def spawn(f):
+    def fun(pipe, x):
+        pipe.send(f(x))
+        pipe.close()
+    return fun
+
+
+def parmap(f, X):
+    pipe = [Pipe() for x in X]
+    proc = [Process(target=spawn(f), args=(c, x))
+            for x, (p, c) in zip(X, pipe)]
+    [p.start() for p in proc]
+    [p.join() for p in proc]
+    return [p.recv() for (p, c) in pipe]
+
+
+class Barrier:
+    """Simple reusable semaphore barrier.
+
+    Python 2.6 doesn't have multiprocessing barriers so we implement this.
+
+    See http://greenteapress.com/semaphores/downey08semaphores.pdf, p. 41.
+    """
+
+    def __init__(self, n, timeout=None):
+        self.n = n
+        self.to = timeout
+        self.count = Value('i', 0)
+        self.mutex = Semaphore(1)
+        self.turnstile1 = Semaphore(0)
+        self.turnstile2 = Semaphore(1)
+
+    def wait(self):
+        if not self.mutex.acquire(timeout=self.to):
+            raise BarrierTimeoutError()
+        self.count.value += 1
+        if self.count.value == self.n:
+            if not self.turnstile2.acquire(timeout=self.to):
+                raise BarrierTimeoutError()
+            self.turnstile1.release()
+        self.mutex.release()
+
+        if not self.turnstile1.acquire(timeout=self.to):
+            raise BarrierTimeoutError()
+        self.turnstile1.release()
+
+        if not self.mutex.acquire(timeout=self.to):
+            raise BarrierTimeoutError()
+        self.count.value -= 1
+        if self.count.value == 0:
+            if not self.turnstile1.acquire(timeout=self.to):
+                raise BarrierTimeoutError()
+            self.turnstile2.release()
+        self.mutex.release()
+
+        if not self.turnstile2.acquire(timeout=self.to):
+            raise BarrierTimeoutError()
+        self.turnstile2.release()
+
+
+class BarrierTimeoutError(Exception):
+    pass