----- Original Message -----
From: "John C Cartwright" <John.C.Cartwright@xxxxxxxx>
To: <caron@xxxxxxxxxxxxxxxx>
Sent: Wednesday, April 17, 2002 9:19 AM
Subject: netCDF Java API question
> Hello John,
>
> I have a question about the Java API that I was hoping that you could
> help me with.
>
> I'm trying to create a simple "stack" of 2D grids using the code listed
> below. The problem is that I'm running out of memory and I assume that
> there must be something I'm doing wrong since it seems unlikely that the
> size of the output file would be constrained by the available RAM. The
> code seems to work OK if I reduce the number of rows and columns.
>
> Can you show me what I'm doing wrong or direct me to a better
> forum/source of information on this?
>
> Thanks!
>
> -- john
Hi John:
Your problem is in allocating the Variable Array all at once, which is an
in-memory array. You really want to allocate only a 2D slice, and write the
slices out sequentially. below is one way to do that.
BTW, in testing this, I discovered an embarrrassing performance bug that
makes things run (blush) 40 time slower in some cases, for example yours! I
just fixed that, and a new release 2.06 is available at
http://www.unidata.ucar.edu/packages/netcdf-java/
you will definitely want to use it!
Also, posting questions to netcdf-java@xxxxxxxxxxxxxxxx lets everyone on
that list see your questions, and possibly learn, if you dont mind exposing
you mistakes. With your permission, I would like to repost this answer
there.
/* old way - uses too much memory
int val=0;
ArrayInt gviA = new ArrayInt.D3(daysSince1900.length,
latDim.getLength(), lonDim.getLength());
Index ima = gviA.getIndex();
// write
for (i=0; i<daysSince1900.length; i++) {
for (j=0; j<latDim.getLength(); j++) {
for (k=0; k<lonDim.getLength(); k++) {
// gviA.setInt(ima.set(i,j,k), gviData[i][j][k]);
gviA.setInt(ima.set(i,j,k), val); // write dummy data for
testing
}
}
val++;
}
// write gviData out to disk
try {
ncfile.write("gvi", gviA);
} catch (IOException e) {
System.err.println("ERROR writing file");
}
*/
// new way, write one 2D slice at a time
int[] origin = new int[3];
int val=0;
ArrayInt gviA = new ArrayInt.D3(1, latDim.getLength(),
lonDim.getLength());
Index ima = gviA.getIndex();
for (i=0; i<daysSince1900.length; i++) {
origin[0] = i; // which slice am i writing ?
for (j=0; j<latDim.getLength(); j++) {
for (k=0; k<lonDim.getLength(); k++) {
gviA.setInt(ima.set(0,j,k), val); // write dummy data for
testing
}
}
// write gviData out to disk
try {
ncfile.write("gvi", origin, gviA);
} catch (IOException e) {
System.err.println("ERROR writing file");
}
val++;
}
