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5<head>
6  <title>FAQ: ABCL - Common Lisp on the JVM</title>
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12<body>
13 <div class="header">
14   <h1>FAQ: ABCL - Common Lisp on the JVM</h1>
15 </div>
16
17<!--#include virtual="left-menu" -->
18
19<div style="margin-left:auto;margin-right:auto;width:20cm">
20<h1>Index</h1>
21<ol id="toc">
22  <li class="topic"><a href="#general">General Questions about ABCL</a>
23    <ol>
24      <li class="question"><a href="#what">What is ABCL?</a></li>
25      <li class="question"><a href="#license">What license is used for ABCL?</a></li>
26      <li class="question"><a href="#bug-reporting">How/Where should I report bugs?</a></li>
27      <li class="question"><a href="#speed">Is ABCL faster or slower than implementation XYZ?</a></li>
28      <li class="question"><a href="#qa">What is the quality of the implementation? How can you tell?</a></li>
29      <li class="question"><a href="#repository">Where is ABCL's source code repository?</a></li>
30      <li class="question"><a href="#documentation">Where is ABCL's documentation?</a></li>
31    </ol>
32  </li> 
33
34  <li class="topic"><a href="#building">Questions about Building ABCL</a>
35    <ol>
36      <li class="question"><a href="#avoiding-recompilation">The Ant build process seems to recompile from scratch each time.  How do I avoid this?</a></li>
37    </ol>
38  </li> 
39
40  <li class="topic"><a href="#running">Questions about Running ABCL</a>
41  <ol>
42    <li class="question">
43      <a href="#maxpermgen-errors">Java is running out of memory
44      with an error reporting something about
45      "java.lang.OutOfMemoryError: PermGen space".  What can I
46      do?</a>
47    </li>
48    <li class="question">
49      <a href="#dotabclrc">What's the name of the startup configuration file?</a>
50    </li>
51  </ol>
52  </li> 
53</ol>
54
55<div class="h2" title="general" id="general">
56<h2 class="topic">General</h2>
57
58<div class="h3" title="what" id="what">
59<h3 class="question">What is ABCL?</h3>
60<p>ABCL stands for Armed Bear Common Lisp.  ABCL is an implementation
61of Common Lisp hosted on the <a href="http://en.wikipedia.org/wiki/Java_virtual_machine">Java Virtual Machine</a>.  With the release of <a
62href="http://common-lisp.net/project/armedbear/#downloads">abcl-1.0</a>,
63Armed Bear Common Lisp is a conforming implementation of the
64<a href="ftp://ftp1.ansi.org/cust_serv/td_10-25-10/ANSI%2BINCITS%2B226-1994%2B(R2004).pdf">ANSI Common Lisp specification</a>.  The required statement of conformance
65is included in the <a href="#user-manual">User Manual</a>.</p>
66
67<p>
68With abcl-1.1.0-dev (aka "ABCL trunk"), now contains a complete
69implementation of the <a
70href="http://www.lisp.org/mop/index.html">AMOP</a>.
71</p>
72</div>
73
74
75<div class="h3" title="license" id="license">
76<h3 class="question">What license is used for ABCL?</h3>
77
78<p>ABCL is distributed under the <a href="http://www.gnu.org/copyleft/gpl.html">GNU General Public License</a> with <a
79href="http://www.gnu.org/software/classpath/license.html">Classpath
80exception</a>. This is the same license as used for JAVA SE and GNU Classpath.</p>
81
82<p>Basically this means you can use ABCL from your application without the
83need to make your own application open source.</p>
84
85<p>
86In general, such usage means that whenever you keep ABCL as a separate
87jar file, you won't have licensing problems. The combining in the
88Classpath exception means that you can
89</p>
90<ol>
91<li>Extend ABCL java classes in your program</li>
92<li>Use ABCL java classes in your program</li>
93<li>Invoke ABCL lisp functions in your program</li>
94</ol>
95<p>
96without having to worry about the licensing. You do have to
97distribute the source code of ABCL (including modifications)
98if you distribute ABCL, but otherwise the license of ABCL is not viral.
99</p>
100</div>
101
102<div class="h3" title="bug-reporting" id="bug-reporting">
103<h3 class="question">How/Where should I report bugs?</h3>
104
105<p>
106The current state of issues can be found in the <a
107href="http://trac.common-lisp.net/armedbear/report/1">ABCL issue
108tracker</a>.  Individuals with an <a
109href="http://en.wikipedia.org/wiki/Openid">OpenID</a> such as a Google
110ID may enter information directly in the bug tracker after
111authenticating by your provider. </p>
112
113<p>
114
115Alternatively, to report a bug, please mail a description of the
116problem, the version of ABCL you are using, and if possible a set of
117steps to reproduce the problem to the <a
118href="http://common-lisp.net/cgi-bin/mailman/listinfo/armedbear-devel">armedbear-devel
119mailing list</a>.  We try to respond within a day at most to messages.
120A convenient way to browse the mailing list archives can be found by
121<a href="http://news.gmane.org/gmane.lisp.armedbear.devel">the gmane
122loom interface to the NNTP group gmane.lisp.armedbear.devel</a>.
123</p>
124
125<p>
126Developers can also usually be found on the
127<a href="http://webchat.freenode.net/?randomnick=1&channels=abcl&prompt=1&uio=d4">#abcl irc channel</a>.
128</p>
129
130<div class="h3" title="speed" id="speed">
131<h3 class="question">Is ABCL faster or slower than implementation XYZ?</h3>
132
133<p>General comparisons are hard to make, the relative speeds depend
134on a lot of factors. For example timing outcomes of specific bits
135of Java may have different timings depending on the settings of
136the HotSpot JIT compiler (if the tests are run on Sun).</p>
137
138<p>Some statements can be made in general though. Due to the fact that
139ABCL has been implemented in Java, it inherits some of the aspects of
140Java itself as well as the fact that it can't directly manipulate
141CPU content. Implementations such as SBCL and Closure CL can do that and
142take that to their advantage: for example in SBCL a boxed fixnum is a
143direct register value, while in ABCL it's encapsulated in an object.</p>
144
145<p>On the other hand, ABCL - like SBCL - supports unboxed fixnums. ABCL's
146fixnums support the full 32 bit range of integer values, while SBCL due
147to its boxing strategy can only use 29 bit integers (on 32bit platforms).</p>
148
149<p>Given ABCL's age - a young project by Lisp standards - there is also
150plenty of room for improvement in the area of execution speed and optimization.
151The project welcomes initiatives to improve performance.</p>
152</div>
153
154
155<div class="h3" title="qa" id="qa">
156<h3 class="question">What is the quality of the implementation? How can you tell?</h3>
157
158<p>The project recognizes there are several dimensions to quality:</p>
159<ol>
160<li> The level of compliance to the standard </li>
161<li> The level of 'usability': whether (or not) the application is able
162  to run existing Lisp code</li>
163</ol>
164
165<p>
166The plan is to ensure that ABCL runs with the software provided by
167<a href="http://www.quicklisp.org/">Quicklisp</a>.  For many packages available from Quicklisp,
168this is already the case.
169</p>
170
171<p>The first item is being measured by running the ANSI test suite compliance
172  tests. The second item is measured by compiling and running the test suite
173  in the <a href="http://maxima.sourceforge.net/">Maxima application</a>.
174  Additionally, compilation of <a href="http://ap5.com/">AP5</a> is used to
175  improve this measure too.</p>
176
177<p>ABCL 1.0.1 fails roughly 20 out of 21702 tests in the ANSI test
178suite in interpreted and compiled modes, a constant number over the
179past releases.</p>
180
181<p>As a measure of 'improvement achieved', the development team refers
182  to the number of failing tests in the Maxima test suite too.
183  ABCL 0.23.0 is able to run the test suite without failures, coming from
184  'only' ca 75 failing tests at the time of 0.15.0, and even 1400 failures
185  around October 2008.</p>
186</div>
187
188<div class="h3" title="repository" id="repository">
189<h3 class="question">Where is ABCL's source code repository?</h3>
190
191<p>The source code may be viewed with a web browser by visiting  <a
192href="http://trac.common-lisp.net/armedbear/browser/trunk/abcl/">http://trac.common-lisp.net/armedbear/browser/trunk/abcl/</a>.
193</p>
194
195<p>If you want to build the source, ABCL trunk,
196can be checked out via <a
197href="http://subversion.apache.org/">Subversion (aka "svn")</a> from
198the URI
199<a href="svn://common-lisp.net/project/armedbear/svn/trunk/abcl/">svn://common-lisp.net/project/armedbear/svn/trunk/abcl/</a>.</p>
200
201<p>
202This ABCL source repository is also exported read-only via HTTP at
203<a href="http://svn.common-lisp.net/armedbear/trunk/abcl">http://svn.common-lisp.net/armedbear/trunk/abcl</a>
204</p>
205</div>
206
207<div class="h3" title="documentation" id="documentation">
208<h3 class="question">Where is ABCL's documentation?</h3>
209
210<p>Documentation on ABCL can be found in several places, depending on the
211  kind of documentation you're looking for.</p>
212
213<ol>
214  <li id="user-manual">Users of the system are invited to start with the <a href="http://code.google.com/p/abcl-dynamic-install/downloads/detail?name=abcl-20120110a.pdf">Armed Bear Common Lisp User Manual</a></li>
215  <li>Our <a href="http://trac.common-lisp.net/armedbear/wiki">wiki</a></li>
216  <li>The <a href="http://trac.common-lisp.net/armedbear/browser">source
217    code (JavaDoc and general comments)</a></li>
218  <li>Specific <a
219href="http://trac.common-lisp.net/armedbear/browser/trunk/abcl/examples">examples</a></li>
220</ol>
221</div>
222
223</div>
224
225<div class="h2" title="Building" id="building">
226<h2 class="topic">Building</h2>
227
228<div class="h3" title="Avoiding recompilation" id="avoiding-recompilation">
229<h3 class="question">The Ant build process seems to recompile from scratch each time.  How do I avoid this?</h3>
230
231<p>
232If the JVM system property <code>abcl.build.incremental</code> is set,
233the Ant build process will attempt to build ABCL incrementally
234by not removing any intermediate results.  The easiest way to enable
235this property is to copy the 'abcl.properties.in' file to
236'abcl.properties', then uncomment the line referencing the setting of
237the <code>abcl.build.incremental</code> property.
238</p>
239</div>
240
241</div>
242
243<div class="h2" title="Running" id="running">
244<h2 class="topic">Running</h2>
245
246<div class="h3" title="Out of Memory errors" id="maxpermgen-errors">
247<h3 class="question">Java is running out of memory with an error reporting something
248about "java.lang.OutOfMemoryError: PermGen space".  What can I
249do?</h3>
250
251<p>
252  You need to increase the memory which the Java allocates for
253  permanent generation ("PermGen)" objects by using the appropriate
254  switch on command line which invokes the JVM hosting ABCL.  When the
255  implementation compiles or loads Lisp code, it creates a separate
256  JVM class for each top-level form.  With large workloads, this can
257  overrun the part of memory which Java reserves for storing the class
258  definition which results in the error you are seeing.
259</p>
260
261<p>
262  The exact manner of configuring this option unfortunately varies by
263  Java implementation.  For the Oracle HotSpot 64bit JVM, something
264  like <code>"-d64 -Xmx4g -XX:MaxPermSize=1g
265  -XX:+CMSClassUnloadingEnabled"</code> will not only increase the
266  PermGen space, but will ensure you always invoke the 64bit JVM,
267  increase the maximum memory space available to the Java to 4GiB, and
268  allow the garbage collection of class definitions which are deemed
269  to be unused.
270</p>
271
272<p>
273  If you are compiling ABCL from source, a handy way to have the build
274  process incorporate such runtime flags in the JVM invocation would
275  be to copy the <code>'abcl.properties.in'</code> file to
276  <code>'abcl.properties'</code>, and then ensure that the
277  <code>'java.options'</code> variable is set to the desired options.
278</p>
279
280<div class="h3" title="What is the name of the startup run control script?" id="dotabclrc">
281<h3 class="question">Is there a file that customizes the startup of the ABCL process?</h3>
282
283<p>
284  The file <code>~/.abclrc</code> is loaded by the implementation if the <code>--noinit</code> flag is not specified.
285</p>
286</div>
287</div>
288
289</div>
290
291</div>
292
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