Using setDefaultSet and clone()

[Don Murray]

Hi Martin-

I've got a fix for this which will be in the next VisAD
release.  If you are building VisAD from source, you can add
the following line in the FlatField.clone() method:

          clone.DoubleRange = new double[TupleDimension][];

just before:

          clone.packValues(unpackValues(true), false);

so it looks like:

.....
     synchronized(DoubleRange) {
       if (!MissingFlag) {
         try {
           clone.DoubleRange = new double[TupleDimension][];
           clone.packValues(unpackValues(true), false);
         }
         catch (VisADException ex) {
           throw new RuntimeException(ex.toString());
         }
.....

Thanks for finding this bug!

Don


Don Murray wrote:
> Hi Martin-
> 
> martin schweitzer wrote:
> 
>> In an application here, we recently found that our main FlatField is
>> storing data as floats rather than doubles.  At first we tried changing
>> the FlatField to a FieldImpl, however that produced problems with
>> DirectManipulationRenderer, so another approach was tried.  We then
>> tried calling setDefaultSet() on our RealTypes, which worked in all
>> ways except our data cloning now appears to not give us a copy as it
>> used to.
>>
>> We were surprised that calling setDefaultSet() appears to change
>> the behaviour of FieldImpl.clone()
> 
> I'm surprised too!  Especially since you are calling copy = true
> on your setSamples (the default).
> 
>> When we run the program below, we get a 'deep copy' when using clone.  
>> If we
>> uncomment the following two lines, we get a 'shallow copy':
>>
>>            // lat.setDefaultSet(new DoubleSet(lat));
>>            // lon.setDefaultSet(new DoubleSet(lon));
>>
>> Any feedback or suggestions will be welcome.
> 
> First, I'd suggest that instead of calling the above, you
> use the RangeSet argument of the FlatField ctor to change the
> type on the fly.  That way you don't change the default set
> for lat and lon RealTypes for other uses:
> 
>     Field myField1 = new FlatField(func, domain, null, null, new Set[] {
>               new DoubleSet(lat), new DoubleSet(lon)}, null);
> 
> 
> However, the problem you are seeing stems from the way the
> backing DoubleRange is not recreated as it is for the FloatRange.
> So, the two FlatFields hold the same backing store array and
> when you call setSamples on the second field, you end up modifying
> the backing store of the first since the DoubleRange is shared.
> 
> I'll need others to help figure out a work around for this and
> then we'll get back to you.
> 
> Don
>> Regards,
>> Martin
>>
>> Here is the program:
>>
>> import visad.*;
>>
>> public class FlatFieldTest
>> {
>>    public static void main(String[] args)
>>    {
>>        try {
>>            RealType lat = RealType.getRealType("Latitude");
>>            RealType lon = RealType.getRealType("Longitude");
>>            RealTupleType range = new RealTupleType(lat, lon);
>>            RealType time = RealType.getRealType("time");
>> *            // If the following two lines are commented out, then
>>            // clone works...
>>            // lat.setDefaultSet(new DoubleSet(lat));
>>            // lon.setDefaultSet(new DoubleSet(lon));
>> *
>>            double samples[][] = {{1, 2}};
>>            Set domain = new 
>> Gridded1DDoubleSet(RealType.getRealType("time"),
>> samples, 2);
>>            FunctionType func = new FunctionType(time, range);
>>            Field myField1 = new FlatField(func, domain);
>>
>>            double[][] values = new double[2][2];
>>            values[0][0] = 100;
>>            values[0][1] = 200;
>>            myField1.setSamples(values);
>>            values[0][0] = 130;
>>            values[0][1] = 180;
>>
>>            Field myField2 = (FieldImpl)((FieldImpl)myField1).clone();
>>            myField2.setSamples(values);
>>
>>            System.out.println("ff1" + myField1);
>>            System.out.println("ff1" + myField2);
>>        } catch (Exception e) {
>>            System.out.println(e.toString());
>>        }
>>    }
>> }
>>
>> *Output when the lines are commented out:*
>> ff1: FlatField
>>    (time -> (Latitude, Longitude))
>> (100.0, 0.0), (200.0, 0.0)
>>
>>
>> ff2: FlatField
>>    (time -> (Latitude, Longitude))
>> (130.0, 0.0), (180.0, 0.0)
>>
>> *Output when the lines are uncommented:*
>> ff1: FlatField
>>    (time -> (Latitude, Longitude))
>> (130.0, 0.0), (180.0, 0.0)
>>
>>
>> ff2: FlatField
>>    (time -> (Latitude, Longitude))
>> (130.0, 0.0), (180.0, 0.0)
>>
> 

-- 
*************************************************************
Don Murray                               UCAR Unidata Program
dmurray at unidata.ucar.edu                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
*************************************************************


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