diff options
Diffstat (limited to 'system/doc/efficiency_guide/functions.xml')
| -rw-r--r-- | system/doc/efficiency_guide/functions.xml | 40 |
1 files changed, 12 insertions, 28 deletions
diff --git a/system/doc/efficiency_guide/functions.xml b/system/doc/efficiency_guide/functions.xml index 0a8ee7eb34..f3d6b59e49 100644 --- a/system/doc/efficiency_guide/functions.xml +++ b/system/doc/efficiency_guide/functions.xml @@ -4,7 +4,7 @@ <chapter> <header> <copyright> - <year>2001</year><year>2017</year> + <year>2001</year><year>2022</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -158,22 +158,23 @@ explicit_map_pairs(Map, Xs0, Ys0) -> <section> <title>Function Calls</title> - <p>This is an intentionally rough guide to the relative costs of - different calls. It is based on benchmark figures run on - Solaris/Sparc:</p> + <p>This is a rough hierarchy of the performance of the + different types of function calls:</p> <list type="bulleted"> <item>Calls to local or external functions (<c>foo()</c>, <c>m:foo()</c>) are the fastest calls.</item> <item>Calling or applying a fun (<c>Fun()</c>, <c>apply(Fun, [])</c>) - is about <em>three times</em> as expensive as calling a local - function.</item> + is just a little slower than external calls.</item> <item>Applying an exported function (<c>Mod:Name()</c>, - <c>apply(Mod, Name, [])</c>) is about twice as expensive as calling - a fun or about <em>six times</em> as expensive as calling a local - function.</item> + <c>apply(Mod, Name, [])</c>) where the number of arguments is known + at compile time is next.</item> + + <item>Applying an exported function (<c>apply(Mod, Name, Args)</c>) + where the number of arguments is not known at compile time is the + least efficient.</item> </list> <section> @@ -187,25 +188,8 @@ explicit_map_pairs(Map, Xs0, Ys0) -> in a hash table. It is therefore always slower than a direct call or a fun call.</p> - <p>It no longer matters (from a performance point of view) - whether you write:</p> - - <code type="erl"> -Module:Function(Arg1, Arg2)</code> - - <p>or:</p> - - <code type="erl"> -apply(Module, Function, [Arg1,Arg2])</code> - - <p>The compiler internally rewrites the latter code into the - former.</p> - - <p>The following code is slightly slower because the shape of the - list of arguments is unknown at compile time.</p> - - <code type="erl"> -apply(Module, Function, Arguments)</code> + <p>Caching callback functions into funs may be more efficient + in the long run than apply calls for frequently-used callbacks.</p> </section> </section> |