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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE chapter SYSTEM "chapter.dtd">
<chapter>
<header>
<copyright>
<year>2001</year><year>2016</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
</legalnotice>
<title>Introduction</title>
<prepared>Bjorn Gustavsson</prepared>
<docno></docno>
<date>2007-11-21</date>
<rev></rev>
<file>introduction.xml</file>
</header>
<section>
<title>Purpose</title>
<quote><p>"Premature optimization is the root of all evil"
(D.E. Knuth)</p></quote>
<p>Efficient code can be well-structured and clean, based
on a sound overall architecture and sound algorithms.
Efficient code can be highly implementation-code that bypasses
documented interfaces and takes advantage of obscure quirks in
the current implementation.</p>
<p>Ideally, your code only contains the first type of efficient
code. If that turns out to be too slow, profile the application
to find out where the performance bottlenecks are and optimize only the
bottlenecks. Let other code stay as clean as possible.</p>
<p>Fortunately, compiler and runtime optimizations introduced in
Erlang/OTP R12B makes it easier to write code that is both clean and
efficient. For example, the ugly workarounds needed in R11B and earlier
releases to get the most speed out of binary pattern matching are
no longer necessary. In fact, the ugly code is slower
than the clean code (because the clean code has become faster, not
because the uglier code has become slower).</p>
<p>This Efficiency Guide cannot really teach you how to write efficient
code. It can give you a few pointers about what to avoid and what to use,
and some understanding of how certain language features are implemented.
This guide does not include general tips about optimization that
works in any language, such as moving common calculations out of loops.</p>
</section>
<section>
<title>Prerequisites</title>
<p>It is assumed that you are familiar with the Erlang programming
language and the OTP concepts.</p>
</section>
</chapter>
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