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Merged
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Feb 14, 2017
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Update readme #21

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4fffc3f
Various updates to README.rst
zware Feb 11, 2017
ca7c4f6
Rewrap at 80 columns
zware Feb 11, 2017
a5ebe4b
Capitalize the 'H' in GitHub
zware Feb 11, 2017
5bbcd3a
Soften verbose testing section
zware Feb 11, 2017
5a20814
Fix awkward construction in LTO section
zware Feb 12, 2017
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Rewrap at 80 columns 
[skip ci]
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@zware
zware committed Feb 14, 2017
commit ca7c4f6c560de56e0d4c741b21808978321cc869
103 changes: 53 additions & 50 deletions README.rst
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Expand Up @@ -15,6 +15,7 @@ reserved.

See the end of this file for further copyright and license information.


Using Python
------------

Expand All @@ -36,14 +37,14 @@ On Unix, Linux, BSD, OSX, and Cygwin::

This will install Python as python3.

You can pass many options to the configure script; run ``./configure --help`` to
find out more. On OSX and Cygwin, the executable is called ``python.exe``;
You can pass many options to the configure script; run ``./configure --help``
to find out more. On OSX and Cygwin, the executable is called ``python.exe``;
elsewhere it's just ``python``.

On Mac OS X, if you have configured Python with ``--enable-framework``, you should
use ``make frameworkinstall`` to do the installation. Note that this installs the
Python executable in a place that is not normally on your PATH, you may want to
set up a symlink in ``/usr/local/bin``.
On Mac OS X, if you have configured Python with ``--enable-framework``, you
should use ``make frameworkinstall`` to do the installation. Note that this
installs the Python executable in a place that is not normally on your PATH,
you may want to set up a symlink in ``/usr/local/bin``.

On Windows, see `PCbuild/readme.txt
<https://github.com/python/cpython/blob/master/PCbuild/readme.txt>`_.
Expand All @@ -57,54 +58,55 @@ For example::
make
make test

(This will fail if you *also* built at the top-level directory.
You should do a ``make clean`` at the toplevel first.)
(This will fail if you *also* built at the top-level directory. You should do
a ``make clean`` at the toplevel first.)

To get an optimized build of Python, ``configure --enable-optimizations`` before
you run ``make``. This sets the default make targets up to enable Profile Guided
Optimization (PGO) and may be used to auto-enable Link Time Optimization (LTO)
on some platforms. For more details, see the sections below.
To get an optimized build of Python, ``configure --enable-optimizations``
before you run ``make``. This sets the default make targets up to enable
Profile Guided Optimization (PGO) and may be used to auto-enable Link Time
Optimization (LTO) on some platforms. For more details, see the sections
below.


Profile Guided Optimization
---------------------------

PGO takes advantage of recent versions of the GCC or Clang compilers.
If ran, ``make profile-opt`` will do several steps.
PGO takes advantage of recent versions of the GCC or Clang compilers. If ran,
``make profile-opt`` will do several steps.

First, the entire Python directory is cleaned of temporary files that
may have resulted in a previous compilation.
First, the entire Python directory is cleaned of temporary files that may have
resulted in a previous compilation.

Then, an instrumented version of the interpreter is built, using suitable
compiler flags for each flavour. Note that this is just an intermediary
step and the binary resulted after this step is not good for real life
workloads, as it has profiling instructions embedded inside.
compiler flags for each flavour. Note that this is just an intermediary step
and the binary resulted after this step is not good for real life workloads, as
it has profiling instructions embedded inside.

After this instrumented version of the interpreter is built, the Makefile
will automatically run a training workload. This is necessary in order to
profile the interpreter execution. Note also that any output, both stdout
and stderr, that may appear at this step is suppressed.
After this instrumented version of the interpreter is built, the Makefile will
automatically run a training workload. This is necessary in order to profile
the interpreter execution. Note also that any output, both stdout and stderr,
that may appear at this step is suppressed.

Finally, the last step is to rebuild the interpreter, using the information
collected in the previous one. The end result will be a Python binary
that is optimized and suitable for distribution or production installation.
collected in the previous one. The end result will be a Python binary that is
optimized and suitable for distribution or production installation.


Link Time Optimization
----------------------

Enabled via configure's ``--with-lto`` flag. LTO takes advantages of recent
compiler toolchains' ability to optimize across the otherwise arbitrary ``.o`` file
boundary when building final executables or shared libraries for additional
performance gains.
compiler toolchains' ability to optimize across the otherwise arbitrary ``.o``
file boundary when building final executables or shared libraries for
additional performance gains.


What's New
----------

We have a comprehensive overview of the changes in the `What's New in
Python 3.7 <https://docs.python.org/3.7/whatsnew/3.7.html>`_ document. For a
more detailed change log, read `Misc/NEWS
We have a comprehensive overview of the changes in the `What's New in Python
3.7 <https://docs.python.org/3.7/whatsnew/3.7.html>`_ document. For a more
detailed change log, read `Misc/NEWS
<https://github.com/python/cpython/blob/master/Misc/NEWS>`_, but a full
accounting of changes can only be gleaned from the `commit history
<https://github.com/python/cpython/commits/master>`_.
Expand Down Expand Up @@ -144,11 +146,11 @@ the `Porting HOWTO <https://docs.python.org/3/howto/pyporting.html>`_.
Testing
-------

To test the interpreter, type ``make test`` in the top-level directory.
The test set produces some output. You can generally ignore the messages
about skipped tests due to optional features which can't be imported.
If a message is printed about a failed test or a traceback or core dump
is produced, something is wrong.
To test the interpreter, type ``make test`` in the top-level directory. The
test set produces some output. You can generally ignore the messages about
skipped tests due to optional features which can't be imported. If a message
is printed about a failed test or a traceback or core dump is produced,
something is wrong.

By default, tests are prevented from overusing resources like disk space and
memory. To enable these tests, run ``make testall``.
Expand All @@ -167,15 +169,15 @@ Installing multiple versions
----------------------------

On Unix and Mac systems if you intend to install multiple versions of Python
using the same installation prefix (``--prefix`` argument to the configure script)
you must take care that your primary python executable is not overwritten by the
installation of a different version. All files and directories installed using
``make altinstall`` contain the major and minor version and can thus live
side-by-side. ``make install`` also creates ``${prefix}/bin/python3`` which refers to
``${prefix}/bin/pythonX.Y``. If you intend to install multiple versions using the
same prefix you must decide which version (if any) is your "primary" version.
Install that version using ``make install``. Install all other versions using
``make altinstall``.
using the same installation prefix (``--prefix`` argument to the configure
script) you must take care that your primary python executable is not
overwritten by the installation of a different version. All files and
directories installed using ``make altinstall`` contain the major and minor
version and can thus live side-by-side. ``make install`` also creates
``${prefix}/bin/python3`` which refers to ``${prefix}/bin/pythonX.Y``. If you
intend to install multiple versions using the same prefix you must decide which
version (if any) is your "primary" version. Install that version using ``make
install``. Install all other versions using ``make altinstall``.

For example, if you want to install Python 2.7, 3.6, and 3.7 with 3.7 being the
primary version, you would execute ``make install`` in your 3.7 build directory
Expand All @@ -197,13 +199,14 @@ Proposals for enhancement
-------------------------

If you have a proposal to change Python, you may want to send an email to the
comp.lang.python or `python-ideas`_ mailing lists for initial feedback. A Python
Enhancement Proposal (PEP) may be submitted if your idea gains ground. All
current PEPs, as well as guidelines for submitting a new PEP, are listed at
comp.lang.python or `python-ideas`_ mailing lists for initial feedback. A
Python Enhancement Proposal (PEP) may be submitted if your idea gains ground.
All current PEPs, as well as guidelines for submitting a new PEP, are listed at
`python.org/dev/peps/ <https://www.python.org/dev/peps/>`_.

.. _python-ideas: https://mail.python.org/mailman/listinfo/python-ideas/


Release Schedule
----------------

Expand All @@ -223,8 +226,8 @@ rights reserved.

Copyright (c) 1991-1995 Stichting Mathematisch Centrum. All rights reserved.

See the file "LICENSE" for information on the history of this software,
terms & conditions for usage, and a DISCLAIMER OF ALL WARRANTIES.
See the file "LICENSE" for information on the history of this software, terms &
conditions for usage, and a DISCLAIMER OF ALL WARRANTIES.

This Python distribution contains *no* GNU General Public License (GPL) code,
so it may be used in proprietary projects. There are interfaces to some GNU
Expand Down