[pypy-commit] extradoc extradoc: in-progress

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: extradoc
Changeset: r5064:89851c7bf6fa
Date: 2013-10-02 17:01 +0200
http://bitbucket.org/pypy/extradoc/changeset/89851c7bf6fa/

Log:	in-progress

diff --git a/talk/pyconza2013/talk.rst b/talk/pyconza2013/talk.rst
new file mode 100644
--- /dev/null
+++ b/talk/pyconza2013/talk.rst
@@ -0,0 +1,220 @@
+
+=======================================
+Software Transactional Memory with PyPy
+=======================================
+
+
+Introduction
+------------
+
+* what is PyPy: an alternative implementation of Python
+
+* main focus is on speed
+
+
+Introduction
+------------
+
+.. image: speed.png
+
+
+SQL Databases by example
+------------------------
+
+::
+
+    BEGIN TRANSACTION;
+    SELECT * FROM ...;
+    UPDATE ...;
+    COMMIT;
+
+
+Python by example
+-----------------
+
+::
+
+    ..
+    x = obj.value
+    obj.value = x + 1
+    ..
+
+
+Python by example
+-----------------
+
+::
+
+    begin_transaction()
+    x = obj.value
+    obj.value = x + 1
+    commit_transaction()
+
+
+Python by example
+-----------------
+
+::
+
+    with atomic:
+        x = obj.value
+        obj.value = x + 1
+
+
+Python by example
+-----------------
+
+::
+
+    with the_lock:
+        x = obj.value
+        obj.value = x + 1
+
+
+Locks != Transactions
+---------------------
+
+::
+
+    BEGIN TRANSACTION;    BEGIN TRANSACTION;    BEGIN..
+    SELECT * FROM ...;    SELECT * FROM ...;    SELEC..
+    UPDATE ...;           UPDATE ...;           UPDAT..
+    COMMIT;               COMMIT;               COMMI..
+
+
+Locks != Transactions
+---------------------
+
+::
+
+    with the_lock:        with the_lock:        with ..
+      x = obj.val           x = obj.val           x =..
+      obj.val = x + 1       obj.val = x + 1       obj..
+
+
+Locks != Transactions
+---------------------
+
+::
+
+    with atomic:          with atomic:          with ..
+      x = obj.val           x = obj.val           x =..
+      obj.val = x + 1       obj.val = x + 1       obj..
+
+
+STM
+---
+
+* Transactional Memory
+
+* advanced magic (but not more so than databases)
+
+
+STM versus HTM
+--------------
+
+* Software versus Hardware
+
+* CPU hardware specially to avoid the high overhead
+
+* too limited for now
+
+
+Example 1
+---------
+
+::
+
+  def apply_interest_rate(self):
+     self.balance *= 1.05
+
+  for account in all_accounts:
+     account.apply_interest_rate()
+
+
+Example 1
+---------
+
+::
+
+  def apply_interest_rate(self):
+     self.balance *= 1.05
+
+  for account in all_accounts:
+     add_task(account.apply_interest_rate)
+  run_tasks()
+
+
+Internally
+----------
+
+* `run_all_tasks()` manages a pool of threads
+
+* each thread runs tasks in a `with atomic`
+
+
+Example 2
+---------
+
+::
+
+  def next_iteration(all_trains):
+     for train in all_trains:
+        start_time = ...
+        for othertrain in train.dependencies:
+           if ...:
+              start_time = ...
+        train.start_time = start_time
+
+
+Example 2
+---------
+
+::
+
+  def compute(train):
+     ...
+
+  def next_iteration(all_trains):
+     for train in all_trains:
+        add_task(compute, train)
+     run_all_tasks()
+
+
+By the way
+----------
+
+* STM replaces the GIL
+
+* any existing multithreaded program runs on multiple cores
+
+
+Current status
+--------------
+
+* 
+
+
+
+User feedback
+-------------
+
+::
+
+  Detected conflict:
+    File "foo.py", line 17, in walk
+      if node.left not in seen:
+  Transaction aborted, 0.000047 seconds lost
+
+
+User feedback
+-------------
+
+::
+
+  Forced inevitable:
+    File "foo.py", line 19, in walk
+      print >> log, logentry
+  Transaction blocked others for 0.xx seconds
+
+(not implemented yet)