Thanks for this code.
I have actually not been able to make the 'read file' test faster, even
when using a directory with 100+ files ( for i in `seq 1 100`; do touch
testdir/$i; done ).
With 100 files, for instance, I still get 'file list' test to execute
faster:
list time=0.62306ms
read time=0.64366ms
Otis
--- Hani Suleiman <[EMAIL PROTECTED]> wrote:
> I've run this test and listing files is pretty consistently faster
> than
> opening and reading a file. The list approach becomes slower than the
>
> file when there are around 20+ files in the directory, so if a
> solution
> whereby timestamps are put in a dedicated dir is put in place, it's
> consistently faster than reading a file. I'm including my micro
> benchmark inline, so feel free to run it and improve either time ;)
>
> For writing, the stamp-in-name solution is faster (obviously) since
> we're just creating an empty file, vs creating a file and writing
> into
> it.
>
> Also I think that holding the file open is probably a bad idea, given
>
> that it'd rule out multiple VM's using the same index.
>
> public class FileTest
> {
> static File dir = new File("testdir");
> static class TimestampFileFilter implements FileFilter
> {
> private String name;
>
> TimestampFileFilter(String name)
> {
> this.name = name;
> }
>
> public boolean accept(File pathname)
> {
> return pathname.getName().startsWith(name + ".");
> }
> }
>
> public static long testFileList(String name)
> {
> TimestampFileFilter filter = new TimestampFileFilter(name);
> File[] files = dir.listFiles(filter);
> long latest = 0;
> for(int i = 0; i < files.length; i++)
> {
> File timestampFile = files[i];
> String fileName = timestampFile.getName();
> long timestamp =
> Long.parseLong(fileName.substring(fileName.lastIndexOf('.') + 1));
> if(timestamp > latest) latest = timestamp;
> }
> return latest;
> }
>
> public static long testReadFile(File file) throws IOException
> {
> FileInputStream fis = new FileInputStream(file);
> DataInputStream dis = new DataInputStream(fis);
> long timestamp = dis.readLong();
> fis.close();
> return timestamp;
> }
>
> public static void main(String[] args) throws IOException
> {
> dir.mkdir();
> File file = new File(dir, "blah.1234");
> FileOutputStream fos = new FileOutputStream(new File(dir,
> "timestamp"));
> DataOutputStream dos = new DataOutputStream(fos);
> dos.writeLong(System.currentTimeMillis());
> fos.close();
> file.createNewFile();
> long now = System.currentTimeMillis();
> int iterations = 100000;
> for(int i=0;i<iterations;i++)
> {
> testFileList("blah");
> }
> System.out.println("list time=" +
> ((double)(System.currentTimeMillis()-now)/iterations) + "ms");
> for(int i = 0; i < iterations; i++)
> {
> testReadFile(new File(dir, "timestamp"));
> }
> System.out.println("read time=" +
> ((double)(System.currentTimeMillis() - now) / iterations) + "ms");
> }
> }
>
>
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