Xor News

I sat under Dr. Lennox’s teaching for a week some years back and really enjoyed it. So I anticipated that I would like this book and I have not been disappointed. The book is very readable and very well reasoned. All but the last 30 pages have a very nice flow to them — I don’t know what happened in that end part, either the editor got tired, or perhaps I got tired, but things seemed like they repeated themselves a lot.

Dr. Lennox knows a lot about a broad range of subjects. I think he knows more than I do about every area, even those that I consider my professional specialties. His sections on information conservation in algorithmic design were very insightful and clear.

I have been looking for some time now to see what ever became of the line of reasoning that A. E. Wilder-Smith brought out some years back regarding the shortcomings of the Miller/Urey experiments on spontaneous creation of amino acids from chemical stew triggered by the application of high voltages. If you have only had the standard text-book understanding of Miller’s experiment, Wilder-Smith’s explanation of the requirement that all amino acids that go into making life-as-we-know-it take the L-form simply devastates the Miller results. I have wondered for some time why no one seems to make more of this? Who would carry on Wilder-Smith’s intellectual legacy? I’ve found it in Dr. Lennox’s fine book. He applies further statistical analysis to the generation of amino acid chains, showing that in addition to the L-form requirement all of the bonds must be peptide bonds. This reduces the likelihood, not that further help was needed, by another factor of 2^100 (for chains 100 amino acids in length), that Miller-type amino acid chains would be suitable for life.

One of the things I enjoyed most about the book was the precision with which Dr. Lennox put forward the dichotomies between religion and science. In fact, in contrast to how we most often tend to phrase the debate, Dr. Lennox argued forcefully that the real debate is between theism and atheism, not between science and religion. His arguments on this were backed up with examples from Galileo to Dawkins and will be very helpful in reframing the debate in the coming months.

Highly recommend this book to anyone interested in keeping up with the current wave of thought on this subject.

Full Bibliographic entry:
God’s Undertaker: Has Science Buried God?, John C. Lennox, Lion Hudson plc, Oxford England 2007.
ISBN: 978 0 7459 5303 8

The boy passed his driver’s test today, he did a great job. This definitely feels like the beginning of a new era.

The enterprise and presentation layers of one of the VLDB Data Warehouse (DW) projects that I work on is date range partitioned. This allows us to easily create a sliding window of data that is as big as we can handle given the storage constraints. Because we do partition maintenance operations quite often, we don’t use any global indexes — all of our indexes are local prefix indexes. This impacts primary key index generation.

If the table is created with a primary key constraint

    CREATE TABLE mydata (
         part    TIMESTAMP NOT NULL,
         id        NUMBER NOT NULL,
         title    VARCHAR2(256)
     );
     ALTER TABLE mydata ADD
         (CONSTRAINT pk_mydata PRIMARY KEY(part,id));

Then what you get is a global non-partitioned primary key. One common piece of DW advice is to just not use primary keys at all, but this removes some of the self-documentation that exists in the schema that would be available to both the Cost Based Optimizer and any data modeling tools that might be used by a future DBA or programmer.

Here is what I have come up with that preserves the documentation and creates a LOCAL partitioned index for the primary key fields (Oracle 10g).

   CREATE TABLE mydata (
         part    TIMESTAMP NOT NULL,
         id        NUMBER NOT NULL,
         title    VARCHAR2(256)
     );
    ALTER TABLE mydata ADD
      (CONSTRAINT pk_mydata  PRIMARY KEY (part,id)
      DISABLE NOVALIDATE;
    ALTER TABLE mydata MODIFY CONSTRAINT pk_mydata RELY;
    CREATE INDEX mydata_pk_idx
         ON mydata(part,id) LOCAL
         COMPUTE STATISTICS PARALLEL
/

So now the primary key is there in the user_constraints table for everyone to find. It can be used by the optimizer if needed, but it is not enforced. The index created over the columns that I intend to function as primary key columns is created as a local index and each local index chunk lives in the partition with the data that it indexes. This allows the partition maintenance operations to slide the window forward one date range increment as needed without any indexes becoming unusable.

10,000 sheep all facing left for $200. Why? I have absolutely no idea, but it does strike my fancy somehow. The boy thought it was pretty funny too. That is sad for him if he grows up finding humor in the same things as the old man, eh?

Bill: What happens if I specify -Xmx multiple times on the command line?
Me: I don’t know, let’s find out.

java -Xms1024m -Xmx99999 -Xmx1024m -version
java version "1.5.0_13"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_13-b05-237)
Java HotSpot(TM) Client VM (build 1.5.0_13-119, mixed mode)

java -Xms1024m -Xmx1024m -Xmx99999 -version
Error occurred during initialization of VM
Incompatible initial and maximum heap sizes specified
Abort trap

Me: The last one always wins.

Suppose you have a Java interface

   public interface Filter {
       int filter(Payload p);
       int filter(java.util.Collection plist);
   }

and an abstract class that implements the interface:

   public abstract class AbstractFilter implements Filter {
        public filter(java.util.Collection plist) {
             for (Payload p : plist) {
                  filter(p);
              }
         }
     }

I sometimes do stuff like this, providing convenience methods in an
abstract base class to enrich an API without putting a burden
on those wishing to implement it, and not tempting anyone to
cut-and-paste a bunch of code around.

Since the filter(Payload p ) method is declared on the interface and
because AbstractFilter is, well, Abstract, I don’t need to mention
filter(Payload p).

But suppose someone wants to provide an implementation:

   public class FooFilter extends AbstractFilter {
      @Override
      public int filter(Payload p) {
          ...
      }
   }

This fails on JDK 1.5 with “method does not override a method from its superclass”.
This will compile without warning on JDK 1.6, and we could just run around and tell
everyone not to use @Override in that situation, but, it’s clearer and better for everyone
and compiles without warnings in both JDK 1.5 and 1.6 if we just add this line to
the AbstractFilter class

    public abstract int filter(Payload p);

This is nice because it gives a place to put some javadoc for the AbstractFilter class,
returns search results if someone is grepping the source for filter methods, and it
allows the @Override to work as it should.

So +3 and -0, on that. It is an all around winner.

From The Name Above Every Name: being Papers on the Excellency, Exaltation and Supremacy of Christ, Edward Dennet, published in London by G. Morrish, n.d.

But when Christ had accomplished the work of atonement, glorifying God in all that He is, having been made sin for us, the veil behind which God had dwelt, and which had concealed Him from His people, was rent in twain from the top to the bottom, and God could righteously gratify His own heard in coming out into the full display of what He is as revealed in Christ on the ground of redemption.

While your English lit teacher might have a fit over the Pauline structure of that sentence, and I readily admit that they don’t write them that way any more, there is a lot packed in there that is worth unpacking.
(more…)

Thanks to a little help from the JRuby user mailing list, I learned that the behavior we had been seeing is not a bug. Local variables that come from an eval are created in ThreadLocal storage. I think I already should have know this as I was not having similar issues with global variables.

But in order to keep multiple users from interfering with each other and never being able to use local variables, I changed our RubyConsole object to run on its own thread. It now implements the HttpSessionBindingListener interface so that I can properly cleanup when the session expires. So there is happiness in JRuby integration land again.

I also learned how to capture the stdout and stderr from the JRuby environment and stuff them into ByteArrayOutputStream instances so that I can capture the data and put it on the HTML response along with the toString of any actual RubyObject that comes back from the eval call. So our JRuby console over AJAX HTTP looks a lot more like what happens in irb on a local terminal. This isn’t currently possible to due with pure BSF, but with a little help from JRuby objects it works by setting up like this when a new BSFManager is created.

            protected ByteArrayOutputStream stdout = new ByteArrayOutputStream();
            Ruby runtime = Ruby.getDefaultInstance();
            IRubyObject out = new RubyIO( runtime, stdout );
            manager.declareBean("stdout", out, RubyIO.class);
            manager.declareBean("defout", out, RubyIO.class);
            manager.declareBean(">", out, RubyIO.class);

And then after every eval call, we can get any available stdout data by calling

            stdout.toString();
            stdout.reset();

There are some other nice ways to do this without BSF and I still need to investigate whether there are improvements in JSR233 in JDK6 that would make this easier. But it works really nicely. Way to go JRuby guys!

Mac OS X Leopard (10.5) has some interesting new output from the ls(1) command. Some files include a “@” or a “+” at the end of the permission string. Like this:
-rw-rw-r–@ 1 12345 Jan 2 file.txt
This is different from the “@” used after the filename to note a symbolic link when using the -F flag. This new marker indicates:

• @ - the presence of extended metadata, see it with “ls -@”
• + - the presence of security ACL info, see it with “ls -e”

The new mdls(1) command might also be if interest for another view of the metadata. The metadata is stored in a file that begins with ._ (dot underscore) and then the normal filename. So the metadata for file.txt would be found in ._file.txt.

The new flags for ls are listed in the Leopard version of the ls man page, but if you’ve upgraded from Tiger you may not see any new man pages. The new man pages are delivered in gzip compressed format but the old man pages are not deleted — apparently a bug in the upgrade installer.

If you want to remove just those man pages that also have a (most likely newer) gzip version, then you can run this as root:

   cd /usr/share/man
   for f in `find . -name “*.gz” -print ; do
       o=`echo $f | sed ’s/\.gz//’`
       if [ -f $o ] ; then
           echo rm $o
       fi
   done

Once you are happy with the output of that, remove the echo statement and the old man pages will be deleted. This isn’t perfect, it still leaves old man pages laying around for things that were part of Tiger but are not part of Leopard. There will still be a man page for niutil(1) , for example, which is obsoleted from Leopard. But I think I can live with that.