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5<head>
6  <title>FAQ: ABCL - Common Lisp on the JVM</title>
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12<body>
13 <div id="title" 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>Frequently Asked Questions about Armed Bear Common Lisp</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://lisp.not.org/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 the release of version 1.1.0, ABCL now contains a complete
69implementation of <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.lisp.not.org/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 href="http://news.gmane.org/gmane.lisp.armedbear.devel">armedbear-devel
118mailing list</a>.  We endeavor to respond within a day to messages.
119</p>
120
121<p>
122Developers can also usually be found on the
123<a href="http://webchat.freenode.net/?randomnick=1&channels=abcl&prompt=1&uio=d4">#abcl irc channel</a>.
124</p>
125
126<div class="h3" title="speed" id="speed">
127<h3 class="question">Is ABCL faster or slower than implementation XYZ?</h3>
128
129<p>General comparisons are hard to make, the relative speeds depend
130on a lot of factors. For example timing outcomes of specific bits
131of Java may have different timings depending on the settings of
132the HotSpot JIT compiler (if the tests are run on Sun).</p>
133
134<p>Some statements can be made in general though. Due to the fact that
135ABCL has been implemented in Java, it inherits some of the aspects of
136Java itself as well as the fact that it can't directly manipulate
137CPU content. Implementations such as SBCL and Closure CL can do that and
138take that to their advantage: for example in SBCL a boxed fixnum is a
139direct register value, while in ABCL it's encapsulated in an object.</p>
140
141<p>On the other hand, ABCL - like SBCL - supports unboxed fixnums. ABCL's
142fixnums support the full 32 bit range of integer values, while SBCL due
143to its boxing strategy can only use 29 bit integers (on 32bit platforms).</p>
144
145<p>Given ABCL's age - a young project by Lisp standards - there is also
146plenty of room for improvement in the area of execution speed and optimization.
147The project welcomes initiatives to improve performance.</p>
148</div>
149
150
151<div class="h3" title="qa" id="qa">
152<h3 class="question">What is the quality of the implementation? How can you tell?</h3>
153
154<p>The project recognizes there are several dimensions to quality:</p>
155<ol>
156<li> The level of compliance to the standard </li>
157<li> The level of 'usability': whether (or not) the application is able
158  to run existing Lisp code</li>
159</ol>
160
161<p>
162The plan is to ensure that ABCL runs with the software provided by
163<a href="http://www.quicklisp.org/">Quicklisp</a>.  For many packages available from Quicklisp,
164this is already the case.
165</p>
166
167<p>The first item is being measured by running the ANSI test suite compliance
168  tests. The second item is measured by compiling and running the test suite
169  in the <a href="http://maxima.sourceforge.net/">Maxima application</a>.
170  Additionally, compilation of <a href="http://ap5.com/">AP5</a> is used to
171  improve this measure too.</p>
172
173<p>ABCL 1.1.1 fails roughly 12 out of 21702 tests in the ANSI test
174suite in interpreted and compiled modes, a constant number over the
175past releases.</p>
176
177<p>As a measure of 'improvement achieved', the development team refers
178  to the number of failing tests in the Maxima test suite too.
179  ABCL 0.23.0 is able to run the test suite without failures, coming from
180  'only' ca 75 failing tests at the time of 0.15.0, and even 1400 failures
181  around October 2008.</p>
182</div>
183
184<div class="h3" title="repository" id="repository">
185<h3 class="question">Where is ABCL's source code repository?</h3>
186
187<p>The source code may be viewed with a web browser by visiting  <a
188href="http://lisp.not.org/trac/armedbear/browser/trunk/abcl/">http://lisp.not.org/trac/armedbear/browser/trunk/abcl/</a>.
189</p>
190
191<p>If you want to build the source, ABCL trunk,
192can be checked out via <a href="http://subversion.apache.org/">Subversion (aka "svn")</a> from
193the URI
194<a href="http://abcl.org/svn/trunk/abcl/">http://abcl.org/svn/trunk/abcl/</a>.</p>
195
196</div>
197
198<div class="h3" title="documentation" id="documentation">
199<h3 class="question">Where is ABCL's documentation?</h3>
200
201<p>Documentation on ABCL can be found in several places, depending on the
202  kind of documentation you're looking for.</p>
203
204<ol>
205  <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-20130607a.pdf">Armed Bear Common Lisp User Manual</a></li>
206  <li>Our <a href="http://lisp.not.org/trac/armedbear/wiki">wiki</a></li>
207  <li>The <a href="http://lisp.not.org/trac/armedbear/browser">source
208    code (JavaDoc and general comments)</a></li>
209  <li>Specific <a href="http://lisp.not.org/trac/armedbear/browser/trunk/abcl/examples">examples</a></li>
210</ol>
211</div>
212
213</div>
214
215<div class="h2" title="Building" id="building">
216<h2 class="topic">Building</h2>
217
218<div class="h3" title="Avoiding recompilation" id="avoiding-recompilation">
219<h3 class="question">The Ant build process seems to recompile from scratch each time.  How do I avoid this?</h3>
220
221<p>
222If the JVM system property <code>abcl.build.incremental</code> is set,
223the Ant build process will attempt to build ABCL incrementally
224by not removing any intermediate results.  The easiest way to enable
225this property is to copy the 'abcl.properties.in' file to
226'abcl.properties', then uncomment the line referencing the setting of
227the <code>abcl.build.incremental</code> property.
228</p>
229</div>
230
231</div>
232
233<div class="h2" title="Running" id="running">
234<h2 class="topic">Running</h2>
235
236<div class="h3" title="Out of Memory errors" id="maxpermgen-errors">
237<h3 class="question">Java is running out of memory with an error reporting something
238about "java.lang.OutOfMemoryError: PermGen space".  What can I
239do?</h3>
240
241<p>
242  You need to increase the memory which the Java allocates for
243  permanent generation ("PermGen)" objects by using the appropriate
244  switch on command line which invokes the JVM hosting ABCL.  When the
245  implementation compiles or loads Lisp code, it creates a separate
246  JVM class for each top-level form.  With large workloads, this can
247  overrun the part of memory which Java reserves for storing the class
248  definition which results in the error you are seeing.
249</p>
250
251<p>
252  The exact manner of configuring this option unfortunately varies by
253  Java implementation.  For the Oracle HotSpot 64bit JVM, something
254  like <code>"-d64 -Xmx4g -XX:MaxPermSize=1g
255  -XX:+CMSClassUnloadingEnabled"</code> will not only increase the
256  PermGen space, but will ensure you always invoke the 64bit JVM,
257  increase the maximum memory space available to the Java to 4GiB, and
258  allow the garbage collection of class definitions which are deemed
259  to be unused.
260</p>
261
262<p>
263  If you are compiling ABCL from source, a handy way to have the build
264  process incorporate such runtime flags in the JVM invocation would
265  be to copy the <code>'abcl.properties.in'</code> file to
266  <code>'abcl.properties'</code>, and then ensure that the
267  <code>'java.options'</code> variable is set to the desired options.
268</p>
269
270<div class="h3" title="What is the name of the startup run control script?" id="dotabclrc">
271<h3 class="question">Is there a file that customizes the startup of the ABCL process?</h3>
272
273<p>
274  The file <code>~/.abclrc</code> is loaded by the implementation if the <code>--noinit</code> flag is not specified.
275</p>
276</div>
277</div>
278
279</div>
280
281</div>
282
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