Re: JAI optimizing..

 a0a <>
Tue, 25 Sep 2007 05:36:27 -0700
Warming up the test seems to make a huge difference. The first
RenderedOp takes about 6 times longer than the whole pojo processing,
but each additional RenderedOp takes only fractions of the total time,
leading me to believe the set-up of JAI is slow, but processing is
extremely fast once you have all the system resources set-up. I
achieved almost a 100 fold speed increase for processing 5 million
coordinates, compared to pojo.

I dived a little deeper in the JAI docs, and essentially tried to
rewrite the setup using RenderableOp and ParameterBlock's instead of
RenderedOp. I got it to compile correctly, but during runtime, I get
an exception that got me rather puzzled:

Exception in thread "main" com.sun.medialib.mlib.mediaLibException:
mediaLib: exception in a native method.
    at com.sun.medialib.mlib.Image.ExtremaLocations(Native Method)
    at JAIDistanceTest.testDistances2(
    at JAIDistanceTest.<init>(
    at JAITest.main(


And here is the code I used, maybe someone can spot the obvious
mistake? Thanks!


int bits[] = new int[] {32};
ColorSpace colorSpace = ColorSpace.getInstance(ColorSpace.CS_GRAY);
ColorModel colorModel = new ComponentColorModel(colorSpace, bits,
false, false, Transparency.OPAQUE, DataBuffer.TYPE_INT);
SampleModel sampleModel =

DataBufferInt dataBufferX = new DataBufferInt(xvalues,
WritableRaster rasterX =
WritableRaster.createWritableRaster(sampleModel, dataBufferX, new
BufferedImage imageX = new BufferedImage(colorModel, rasterX,
false, null);

DataBufferInt dataBufferY = new DataBufferInt(yvalues,
WritableRaster rasterY =
WritableRaster.createWritableRaster(sampleModel, dataBufferY, new
BufferedImage imageY = new BufferedImage(colorModel, rasterY,
false, null);

PlanarImage planarImageX = new RenderedImageAdapter(imageX);
PlanarImage planarImageY = new RenderedImageAdapter(imageY);

RenderingHints renderingHints = new

// create a renderable image with no downsampled piramid
ParameterBlock parameterBlockX = new ParameterBlock();
RenderableImage renderableImageX = JAI.createRenderable("renderable",

// create a renderable image with no downsampled piramid
ParameterBlock parameterBlockY = new ParameterBlock();
RenderableImage renderableImageY = JAI.createRenderable("renderable",

double[] xSub = new double[]{x};
double[] ySub = new double[]{y};

long nanoStart = System.nanoTime();
ParameterBlock parameterBlockSub1 = new ParameterBlock();
RenderableOp renderableOpXSubXRef =
JAI.createRenderable("subtractconst", parameterBlockSub1);

ParameterBlock parameterBlockSub2 = new ParameterBlock();
RenderableOp renderableOpYSubYRef =
JAI.createRenderable("subtractconst", parameterBlockSub2);

ParameterBlock parameterBlockPow1 = new ParameterBlock();
RenderableOp renderableOpXDiff2 = JAI.createRenderable("multiply",

ParameterBlock parameterBlockPow2 = new ParameterBlock();
RenderableOp renderableOpYDiff2 = JAI.createRenderable("multiply",

ParameterBlock parameterBlockSum = new ParameterBlock();
RenderableOp renderableOpSum = JAI.createRenderable("add",

        AffineTransform screenResolution = new AffineTransform();
        RenderContext renderContext = new
RenderedOp renderedOpExtrema =
null, 1, 1, true, 1, renderingHints);

long nanoEnd = System.nanoTime();

List minLocations =

some good references in case you are interested:
(JAI API docs) (sample
(chained calls)
(sun tutorials)

On 24 sep, 20:15, a0a <> wrote:

Hi everyone,

I did a little benchmark on the speedup thatJAIcan bring in
computing the point with minimum distance from a given source point
(x,y) out of an array of x,y coordinates.

I did this both withJAIand by brute-forcing it using a simple
distance check. Although theJAIis very elegant in that it
automatically returns ALL minimum distance points, it is also 6 times
slower than the brute-force method.

I am guessing that I may have gotten something wrong in the set-up,
but since the information onJAIand tutorials are rather scarce or
not working at all, I thought maybe someone here could take a look at

------ this is what I want to do ------

ArrayList<Integer> indexes = new ArrayList<Integer> ();
int closestPoint = Integer.MAX_VALUE;

for (int i = 0; i < xvalues.length; i++)
        int xdiff = xvalues[i] - x;
        int ydiff = yvalues[i] - y;
        int sqr = xdiff* xdiff + ydiff*ydiff;
        if ( sqr == closestPoint )
        if ( sqr < closestPoint )
                closestPoint = sqr;


------ this is what does it, but 6 times slower, inJAI------

double[] xSub = new double[]{x};
double[] ySub = new double[]{y};

RenderedOp renderedOpXSubXRef = SubtractConstDescriptor.create(imageX,
xSub, rh);
RenderedOp renderedOpYSubYRef = SubtractConstDescriptor.create(imageY,
ySub, rh);
RenderedOp renderedOpXDiff2 =
MultiplyDescriptor.create(renderedOpXSubXRef, renderedOpXSubXRef, rh);
RenderedOp renderedOpYDiff2 =
MultiplyDescriptor.create(renderedOpYSubYRef, renderedOpYSubYRef, rh);
RenderedOp renderedOpSum = AddDescriptor.create(renderedOpXDiff2,
renderedOpYDiff2, rh);
RenderedOp renderedOpExtrema = ExtremaDescriptor.create(renderedOpSum,
null, 1, 1, true, 1, rh);

List minLocations =


Of course, right before this code I convert the 2 int[] arrays
containing x values and y values into BufferedImages using a GrayScale
colorspace, 32 bit colorModel with no alpha, no transparency, no
premultiplication. I do not alter the rasters during computation, I
merely fetch the min values from the list "minLocations" afterwards.
Timing it indicates that processing is extremely slow, however, I
still have to rewrite the benchmark to warm up first and redo the test
a number of times, maybe the test may show improvement. However, if
anyone has ideas how to speed up the operation pipe, I am all ears!

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