path: root/system/doc/efficiency_guide/introduction.xml

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<chapter>
  <header>
    <copyright>
      <year>2001</year><year>2017</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.
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          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
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      See the License for the specific language governing permissions and
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    <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>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>