Re: [Cdk-devel] new "IsotopeFactory"

[John M. <joh...@gm...>]

> What does this do? And how will this make things better/faster?

Micro optimisation but - http://docs.oracle.com/javase/6/docs/api/java/lang/String.html#intern%28%29

Basically allows you to have a single reference for the same string. The compiler does this for inline strings
but not when reading from IO. This does use permgen space - but permgen is becoming metaspace
in Java 1.8 - http://java.dzone.com/articles/java-8-permgen-metaspace so don't worry about that.

Example shows that different reference - gets replaced by the same reference:

String a = new String("Carbon");
String b = new String("Carbon"):
a == b 				: false
a.intern() == b.intern() 		: true

> Yeah, some more indices could make sense, but particularly if the
> class is a singleton, so that the indices get reused when ever the
> factory is used. Or not?


Even if not - the indices are relatively quite small.

> OK, another corner of Java I do not know. What a fixed precision
> decimal? How do I use that?


Using arbitrary precession 

1.0 - 0.9 = 0.09999999999999998

Fixed precision means - I am accurate to a fixed precession in this case we would need 1 decimal place. To work
to 1 decimal place we multiple by a factor 10 and can use integers. 

10 - 9 = 1
10/10 - 9/10 = 1/10

Depends what you want, how accurate the masses need to be? This fixed precessions is really only good if you need to
do numerical operations.

> Good idea. I have little experience with binary formats, but worth learning...


Yep, no need for record separators either.

Using streams:

   IsotopeFactory isotopeFactory = IsotopeFactory.getInstance(SilentChemObjectBuilder.getInstance());
            String path = System.getProperty("user.home") + "/bodr-isotopes";
            FileOutputStream fos  = new FileOutputStream(path);
            DataOutput       dout = new DataOutputStream(fos);
            IIsotope[] isotopes = isotopeFactory.getIsotopes();
            dout.writeInt(isotopes.length);
            for (IIsotope isotope : isotopes) {
                dout.writeUTF(isotope.getSymbol());
                dout.writeInt(isotope.getAtomicNumber());
                dout.writeInt(isotope.getMassNumber());
                dout.writeDouble(isotope.getExactMass());
                dout.writeDouble(isotope.getNaturalAbundance());               
            }
            fos.close();

            FileInputStream fin = new FileInputStream(path);
            DataInput din = new DataInputStream(fin);
            int n = din.readInt();
            for (int i = 0; i < n; i++) {
                String symbol    = din.readUTF().intern();
                int    elem      = din.readInt();
                int    mass      = din.readInt();
                double exactMass = din.readDouble();
                double natAbund  = din.readDouble();
            }
            fin.close();

or using buffers - strings are a little tricky but actually you can just omit them and load the symbols elsewhere. Note the buffers + memory mapping
is really really fast :-). File size is a bout the same as the text as '0.0' takes up 8 bytes when written as binary.

IsotopeFactory isotopeFactory = IsotopeFactory.getInstance(SilentChemObjectBuilder.getInstance());
            String path = System.getProperty("user.home") + "/bodr-isotopes";


            IIsotope[] isotopes = isotopeFactory.getIsotopes();
            ByteBuffer bout = ByteBuffer.allocate(100000);
            bout.putInt(isotopes.length);
            for (IIsotope isotope : isotopes) {
                // chars a little more tricky
                bout.putInt(isotope.getAtomicNumber());
                bout.putInt(isotope.getMassNumber());
                bout.putDouble(isotope.getExactMass());
                bout.putDouble(isotope.getNaturalAbundance());
            }

            bout.limit(bout.position()).position(0);            
            FileChannel fc = new FileOutputStream(path).getChannel();
            fc.write(bout);
            fc.close();

            FileChannel fcIn = new FileInputStream(path).getChannel();
            ByteBuffer bin = fcIn.map(FileChannel.MapMode.READ_ONLY,
                                      0,
                                      new File(path).length());
            int n = bin.getInt();
            for (int i = 0; i < n; i++) {
                int elem         = bin.getInt();
                int mass         = bin.getInt();
                double exactMass = bin.getDouble();
                double natAbund  = bin.getDouble();
            }
            fcIn.close();

On 16 Oct 2013, at 11:52, Egon Willighagen <ego...@gm...> wrote:

> John,
> 
> On Wed, Oct 16, 2013 at 12:45 PM, John May <joh...@gm...> wrote:
>> Do you want me to patch now? Changes suggested below can be done afterwards
> 
> I like to do them now. So that I learn, but please educate me a bit...
> 
>> - intern the string symbol, 'fields[0].trim().intern()'
> 
> What does this do? And how will this make things better/faster?
> 
>> - HashMaps for symbol/element lookup, TreeMap for the range lookups.
> 
> Yeah, some more indices could make sense, but particularly if the
> class is a singleton, so that the indices get reused when ever the
> factory is used. Or not?
> 
>> - could store the decimal numbers as fixed precision rather than arbitrary precision (floating point). Probably not worth it though.
> 
> OK, another corner of Java I do not know. What a fixed precision
> decimal? How do I use that?
> 
>> - I don't think there is much benefit to have it as a singleton, if it loads faster enough let the invokee decided when to
>>  keep it around.
> 
> Possibly. What about indices? See above...
> 
>> - unsupported methods could throw UnsupportedOperationException
> 
> Yeah, I have considered that... I think post 1.5 I will propose my
> patch to split mutable/immutable CDK interfaces...
> 
>> - if the code generate the file from the XML maybe writing in binary instead -  smaller, faster to read, can only be changed using the BODR xml?
> 
> Good idea. I have little experience with binary formats, but worth learning...
> 
> Egon
> 
> 
> -- 
> Dr E.L. Willighagen
> Postdoctoral Researcher
> Department of Bioinformatics - BiGCaT
> Maastricht University (http://www.bigcat.unimaas.nl/)
> Homepage: http://egonw.github.com/
> LinkedIn: http://se.linkedin.com/in/egonw
> Blog: http://chem-bla-ics.blogspot.com/
> PubList: http://www.citeulike.org/user/egonw/tag/papers
> ORCID: 0000-0001-7542-0286
> 
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