diff options
Diffstat (limited to 'system')
| -rw-r--r-- | system/COPYRIGHT | 128 | ||||
| -rw-r--r-- | system/doc/design_principles/sup_princ.xml | 4 | ||||
| -rw-r--r-- | system/doc/efficiency_guide/myths.xml | 108 | ||||
| -rw-r--r-- | system/doc/efficiency_guide/part.xml | 1 | ||||
| -rw-r--r-- | system/doc/efficiency_guide/retired_myths.xml | 63 | ||||
| -rw-r--r-- | system/doc/tutorial/complex6_nif.c | 2 |
6 files changed, 218 insertions, 88 deletions
diff --git a/system/COPYRIGHT b/system/COPYRIGHT index ef76b66f6b..ed06dcf69c 100644 --- a/system/COPYRIGHT +++ b/system/COPYRIGHT @@ -22,6 +22,17 @@ limitations under the License. %CopyrightEnd% --------------------------------------------------------------------------- +[stdlib, compiler] + +* assert.hrl is Copyright (C) 2004-1016 Richard Carlsson, Mickaël Rémond +* array.erl is Copyright (C) 2006-2016 Richard Carlsson and Ericsson AB +* gb_trees.erl is Copyright (C) 1999-2001 Sven-Olof Nyström, Richard Carlsson +* gb_sets.erl is Copyright (C) 1999-2001 Richard Carlsson, Sven-Olof Nyström +* proplists.erl is Copyright (C) 2000-2003 Richard Carlsson +* cerl{_trees,_clauses}.erl are Copyright (C) 1999-2002 Richard Carlsson +* cerl_inline.erl is Copyright (C) 1999-2002 Richard Carlsson + +--------------------------------------------------------------------------- [PCRE] PCRE LICENCE @@ -190,32 +201,108 @@ terms specified in this license. */ --------------------------------------------------------------------------- +[dialyzer] + +%% Copyright 1997-2016 Tobias Lindahl, Stavros Aronis, Kostis Sagonas, +%% Richard Carlsson, et al. +%% +%% 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. + +--------------------------------------------------------------------------- +[typer] + +%% Copyright 2006-2016 Bingwen He, Tobias Lindahl, Kostis Sagonas +%% +%% 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. + +--------------------------------------------------------------------------- +[hipe] + +%% Copyright 1997-2016 Erik Stenman (Johansson), Kostis Sagonas, +%% Richard Carlsson, Tobias Lindahl, Per Gustafsson, et al. +%% +%% 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. + +--------------------------------------------------------------------------- [edoc, syntax_tools] -%% ===================================================================== -%% This library is free software; you can redistribute it and/or modify -%% it under the terms of the GNU Lesser General Public License as -%% published by the Free Software Foundation; either version 2 of the -%% License, or (at your option) any later version. +%% Copyright 1997-2016 Richard Carlsson <[email protected]> +%% +%% 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. %% -%% This library is distributed in the hope that it will be useful, but -%% WITHOUT ANY WARRANTY; without even the implied warranty of -%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU -%% Lesser General Public License for more details. +%% Alternatively, you may use this file under the terms of the GNU Lesser +%% General Public License (the "LGPL") as published by the Free Software +%% Foundation; either version 2.1, or (at your option) any later version. +%% If you wish to allow use of your version of this file only under the +%% terms of the LGPL, you should delete the provisions above and replace +%% them with the notice and other provisions required by the LGPL; see +%% <http://www.gnu.org/licenses/>. If you do not delete the provisions +%% above, a recipient may use your version of this file under the terms of +%% either the Apache License or the LGPL. + +--------------------------------------------------------------------------- +[eunit] + +%% Copyright 2004-2016 Richard Carlsson <[email protected]>, +%% Mickaël Rémond <[email protected]> %% -%% You should have received a copy of the GNU Lesser General Public -%% License along with this library; if not, write to the Free Software -%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 -%% USA +%% 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> %% -%% $Id$ +%% 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. %% -%% @copyright 2001-2003 Richard Carlsson -%% @author Richard Carlsson <[email protected]> -%% [http://www.csd.uu.se/~richardc/] -%% @version {@vsn} -%% @end -%% ===================================================================== +%% Alternatively, you may use this file under the terms of the GNU Lesser +%% General Public License (the "LGPL") as published by the Free Software +%% Foundation; either version 2.1, or (at your option) any later version. +%% If you wish to allow use of your version of this file only under the +%% terms of the LGPL, you should delete the provisions above and replace +%% them with the notice and other provisions required by the LGPL; see +%% <http://www.gnu.org/licenses/>. If you do not delete the provisions +%% above, a recipient may use your version of this file under the terms of +%% either the Apache License or the LGPL. --------------------------------------------------------------------------- [leex] @@ -269,3 +356,4 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. --------------------------------------------------------------------------- +[typer]
\ No newline at end of file diff --git a/system/doc/design_principles/sup_princ.xml b/system/doc/design_principles/sup_princ.xml index 0a24e97950..c24177d842 100644 --- a/system/doc/design_principles/sup_princ.xml +++ b/system/doc/design_principles/sup_princ.xml @@ -163,7 +163,9 @@ SupFlags = #{strategy => Strategy, ...}</code> SupFlags = #{intensity => MaxR, period => MaxT, ...}</code> <p>If more than <c>MaxR</c> number of restarts occur in the last <c>MaxT</c> seconds, the supervisor terminates all the child - processes and then itself.</p> + processes and then itself. + The termination reason for the supervisor itself in that case will be + <c>shutdown</c>.</p> <p>When the supervisor terminates, then the next higher-level supervisor takes some action. It either restarts the terminated supervisor or terminates itself.</p> diff --git a/system/doc/efficiency_guide/myths.xml b/system/doc/efficiency_guide/myths.xml index 5d3ad78b23..778cd06c09 100644 --- a/system/doc/efficiency_guide/myths.xml +++ b/system/doc/efficiency_guide/myths.xml @@ -24,7 +24,7 @@ The Initial Developer of the Original Code is Ericsson AB. </legalnotice> - <title>The Eight Myths of Erlang Performance</title> + <title>The Seven Myths of Erlang Performance</title> <prepared>Bjorn Gustavsson</prepared> <docno></docno> <date>2007-11-10</date> @@ -35,80 +35,33 @@ <marker id="myths"></marker> <p>Some truths seem to live on well beyond their best-before date, perhaps because "information" spreads faster from person-to-person - than a single release note that says, for example, that funs - have become faster.</p> + than a single release note that says, for example, that body-recursive + calls have become faster.</p> <p>This section tries to kill the old truths (or semi-truths) that have become myths.</p> <section> - <title>Myth: Funs are Slow</title> - <p>Funs used to be very slow, slower than <c>apply/3</c>. - Originally, funs were implemented using nothing more than - compiler trickery, ordinary tuples, <c>apply/3</c>, and a great - deal of ingenuity.</p> - - <p>But that is history. Funs was given its own data type - in R6B and was further optimized in R7B. - Now the cost for a fun call falls roughly between the cost for a call - to a local function and <c>apply/3</c>.</p> - </section> - - <section> - <title>Myth: List Comprehensions are Slow</title> - - <p>List comprehensions used to be implemented using funs, and in the - old days funs were indeed slow.</p> - - <p>Nowadays, the compiler rewrites list comprehensions into an ordinary - recursive function. Using a tail-recursive function with - a reverse at the end would be still faster. Or would it? - That leads us to the next myth.</p> - </section> - - <section> <title>Myth: Tail-Recursive Functions are Much Faster Than Recursive Functions</title> <p><marker id="tail_recursive"></marker>According to the myth, - recursive functions leave references - to dead terms on the stack and the garbage collector has to copy - all those dead terms, while tail-recursive functions immediately - discard those terms.</p> - - <p>That used to be true before R7B. In R7B, the compiler started - to generate code that overwrites references to terms that will never - be used with an empty list, so that the garbage collector would not - keep dead values any longer than necessary.</p> - - <p>Even after that optimization, a tail-recursive function is - still most of the times faster than a body-recursive function. Why?</p> - - <p>It has to do with how many words of stack that are used in each - recursive call. In most cases, a recursive function uses more words - on the stack for each recursion than the number of words a tail-recursive - would allocate on the heap. As more memory is used, the garbage - collector is invoked more frequently, and it has more work traversing - the stack.</p> - - <p>In R12B and later releases, there is an optimization that - in many cases reduces the number of words used on the stack in - body-recursive calls. A body-recursive list function and a - tail-recursive function that calls <seealso - marker="stdlib:lists#reverse/1">lists:reverse/1</seealso> at - the end will use the same amount of memory. - <c>lists:map/2</c>, <c>lists:filter/2</c>, list comprehensions, - and many other recursive functions now use the same amount of space - as their tail-recursive equivalents.</p> - - <p>So, which is faster? - It depends. On Solaris/Sparc, the body-recursive function seems to - be slightly faster, even for lists with a lot of elements. On the x86 - architecture, tail-recursion was up to about 30% faster.</p> - - <p>So, the choice is now mostly a matter of taste. If you really do need - the utmost speed, you must <em>measure</em>. You can no longer be - sure that the tail-recursive list function always is the fastest.</p> + using a tail-recursive function that builds a list in reverse + followed by a call to <c>lists:reverse/1</c> is faster than + a body-recursive function that builds the list in correct order; + the reason being that body-recursive functions use more memory than + tail-recursive functions.</p> + + <p>That was true to some extent before R12B. It was even more true + before R7B. Today, not so much. A body-recursive function + generally uses the same amount of memory as a tail-recursive + function. It is generally not possible to predict whether the + tail-recursive or the body-recursive version will be + faster. Therefore, use the version that makes your code cleaner + (hint: it is usually the body-recursive version).</p> + + <p>For a more thorough discussion about tail and body recursion, + see <url href="http://ferd.ca/erlang-s-tail-recursion-is-not-a-silver-bullet.html">Erlang's Tail Recursion is Not a Silver Bullet</url>.</p> <note><p>A tail-recursive function that does not need to reverse the list at the end is faster than a body-recursive function, @@ -199,6 +152,29 @@ vanilla_reverse([], Acc) -> <p>That was once true, but from R6B the BEAM compiler can see that a variable is not used.</p> + + <p>Similarly, trivial transformations on the source-code level + such as converting a <c>case</c> statement to clauses at the + top-level of the function seldom makes any difference to the + generated code.</p> + </section> + + <section> + <title>Myth: A NIF Always Speeds Up Your Program</title> + + <p>Rewriting Erlang code to a NIF to make it faster should be + seen as a last resort. It is only guaranteed to be dangerous, + but not guaranteed to speed up the program.</p> + + <p>Doing too much work in each NIF call will + <seealso marker="erts:erl_nif#WARNING">degrade responsiveness + of the VM</seealso>. Doing too little work may mean that + the gain of the faster processing in the NIF is eaten up by + the overhead of calling the NIF and checking the arguments.</p> + + <p>Be sure to read about + <seealso marker="erts:erl_nif#lengthy_work">Long-running NIFs</seealso> + before writing a NIF.</p> </section> </chapter> diff --git a/system/doc/efficiency_guide/part.xml b/system/doc/efficiency_guide/part.xml index 6e10a0c031..5673ddd320 100644 --- a/system/doc/efficiency_guide/part.xml +++ b/system/doc/efficiency_guide/part.xml @@ -39,5 +39,6 @@ <xi:include href="drivers.xml"/> <xi:include href="advanced.xml"/> <xi:include href="profiling.xml"/> + <xi:include href="retired_myths.xml"/> </part> diff --git a/system/doc/efficiency_guide/retired_myths.xml b/system/doc/efficiency_guide/retired_myths.xml new file mode 100644 index 0000000000..37f46566cd --- /dev/null +++ b/system/doc/efficiency_guide/retired_myths.xml @@ -0,0 +1,63 @@ +<?xml version="1.0" encoding="utf-8" ?> +<!DOCTYPE chapter SYSTEM "chapter.dtd"> + +<chapter> + <header> + <copyright> + <year>2016</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. + + The Initial Developer of the Original Code is Ericsson AB. + </legalnotice> + <marker id="retired_myths"/> + <title>Retired Myths</title> + <prepared>Bjorn Gustavsson</prepared> + <docno></docno> + <date>2016-06-07</date> + <rev></rev> + <file>retired_myths.xml</file> + </header> + + <p>We belive that the truth finally has caught with the following, + retired myths.</p> + + <section> + <title>Myth: Funs are Slow</title> + <p>Funs used to be very slow, slower than <c>apply/3</c>. + Originally, funs were implemented using nothing more than + compiler trickery, ordinary tuples, <c>apply/3</c>, and a great + deal of ingenuity.</p> + + <p>But that is history. Funs was given its own data type + in R6B and was further optimized in R7B. + Now the cost for a fun call falls roughly between the cost for a call + to a local function and <c>apply/3</c>.</p> + </section> + + <section> + <title>Myth: List Comprehensions are Slow</title> + + <p>List comprehensions used to be implemented using funs, and in the + old days funs were indeed slow.</p> + + <p>Nowadays, the compiler rewrites list comprehensions into an ordinary + recursive function. Using a tail-recursive function with + a reverse at the end would be still faster. Or would it? + That leads us to the myth that tail-recursive functions are faster + than body-recursive functions.</p> + </section> +</chapter> diff --git a/system/doc/tutorial/complex6_nif.c b/system/doc/tutorial/complex6_nif.c index b656ed43ce..f6c06e94f4 100644 --- a/system/doc/tutorial/complex6_nif.c +++ b/system/doc/tutorial/complex6_nif.c @@ -1,4 +1,4 @@ -#include "erl_nif.h" +#include <erl_nif.h> extern int foo(int x); extern int bar(int y); |