Also, because Android is based on the Apache Harmony stack, any library improvements contributed upstream will benefit both projects.
Also, is there a particular use case you're targeting? (Random reads across binary files is pretty abstract, and there might be system tools to help speed things up for special cases, such as BitmapFactory.) j On Sat, May 9, 2009 at 9:37 PM, beekeeper <[email protected]> wrote: > > I've been beating my head against the wall trying to figure out which > file I/O techniques work at speeds comparable to their Java SDK > counterparts, and which don't. I've run benchmarks which indicate, > for example, that a batch operation on a memory mapped ByteBuffer runs > at 1/5 the speed of byte-at-a-time operations on an array-backed > ByteBuffer. Byte-at-a-time I/O on random access files is more than > 100 times slower than other techniques. I've included my benchmark > method and its output (as run on a 2.8MB file on a HTC G1 with Android > 1.1) below. > > My primary questions are: > 1) Has anybody else worked through various I/O techniques under > Android and figured out which are usable and which are too inefficient > to bother with? > 2) Can I expect these libraries to be significantly more efficient in > Android 1.5? > > Question (2) is the really important one. I'll rewrite my apps for > efficiency if I have to, but if the issue is going to be rendered moot > in a matter of weeks, I'd rather not go to quite as much trouble. > > -Beekeeper > > --- > > public void testReading(final RandomAccessFile in) throws > IOException { > // Allocate files and objects outside of timing loops > final FileChannel channel = in.getChannel(); > final int fileSize = (int)channel.size(); > final byte[] testBytes = new byte[fileSize]; > final ByteBuffer buff = ByteBuffer.allocate(fileSize); > final byte[] buffArray = buff.array(); > final int buffBase = buff.arrayOffset(); > > // Read from channel into buffer, and batch read from buffer to > byte array > long time1 = System.currentTimeMillis(); > channel.position(0); > channel.read(buff); > buff.flip(); > buff.get(testBytes); > long time2 = System.currentTimeMillis(); > System.out.println("Fast load: " + (time2 - time1) + "ms"); > > > // Read from channel into buffer, and batch copy from underlying > array > time1 = System.currentTimeMillis(); > channel.position(0); > channel.read(buff); > buff.flip(); > System.arraycopy(buffArray, buffBase, testBytes, 0, > testBytes.length); > time2 = System.currentTimeMillis(); > System.out.println("Another fast load: " + (time2 - time1) + > "ms"); > > // Read from channel into buffer, and get bytes one-by-one from > underlying array > time1 = System.currentTimeMillis(); > channel.position(0); > channel.read(buff); > buff.flip(); > for (int i = 0, j = buffBase, ni = testBytes.length; i < ni; i++, j > ++) > testBytes[i] = buffArray[j]; > time2 = System.currentTimeMillis(); > System.out.println("Fastish load: " + (time2 - time1) + "ms"); > > // Read from channel into buffer, and get bytes one-by-one > time1 = System.currentTimeMillis(); > channel.position(0); > channel.read(buff); > buff.flip(); > for (int i = 0, ni = testBytes.length; i < ni; i++) > testBytes[i] = buff.get(); > buff.flip(); > time2 = System.currentTimeMillis(); > System.out.println("Medium load: " + (time2 - time1) + "ms"); > > // Memory map buffer, and batch read from buffer to byte array > time1 = System.currentTimeMillis(); > final MappedByteBuffer buff2 = channel.map(MapMode.READ_WRITE, 0, > fileSize); > buff2.get(testBytes); > buff2.flip(); > time2 = System.currentTimeMillis(); > System.out.println("Slow load: " + (time2 - time1) + "ms"); > > // Read bytes one-by-one, directly from file > time1 = System.currentTimeMillis(); > in.seek(0); > for (int i = 0, ni = testBytes.length; i < ni; i++) > testBytes[i] = (byte)in.read(); > time2 = System.currentTimeMillis(); > System.out.println("Incredibly slow load: " + (time2 - time1) + > "ms"); > } > > --- > > I/System.out(12168): Fast load: 83ms > I/System.out(12168): Another fast load: 23ms > I/System.out(12168): Fastish load: 1497ms > I/System.out(12168): Medium load: 5507ms > I/System.out(12168): Slow load: 32165ms > D/dalvikvm(12168): GC freed 87347 objects / 2097056 bytes in 242ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 250ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 242ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 249ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 247ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 249ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 242ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 252ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 243ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 249ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 243ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 249ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 243ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 249ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 242ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 250ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 243ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 249ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 245ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 251ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 242ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 250ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 242ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 249ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 244ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 249ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 243ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 250ms > D/dalvikvm(12168): GC freed 87367 objects / 2097144 bytes in 243ms > D/dalvikvm(12168): GC freed 87367 objects / 2097152 bytes in 251ms > I/System.out(12168): Incredibly slow load: 446546ms > > > > > > -- Jeff Sharkey [email protected] --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. 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