Posted by Martin on Nov 18, 2014; 1:11am
URL: https://forum.jogamp.org/Maximum-size-of-CLBuffer-FloatBuffer-tp4033567.html

Hi all,

here is my problem. When I run:

context.createFloatBuffer(bufLength, Mem.WRITE_ONLY);

I need to make sure that "bufLength" is in the range of [0, 2^29-1] otherwise the buffer will throw an error like this:

java.lang.IllegalArgumentException: Negative capacity: -2147483648
        at java.nio.Buffer.<init>(Buffer.java:191)
        at java.nio.ByteBuffer.<init>(ByteBuffer.java:276)
        at java.nio.ByteBuffer.<init>(ByteBuffer.java:284)
        at java.nio.MappedByteBuffer.<init>(MappedByteBuffer.java:89)
        at java.nio.DirectByteBuffer.<init>(DirectByteBuffer.java:119)
        at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:306)
        at com.jogamp.common.nio.Buffers.newDirectByteBuffer(Buffers.java:73)
        at com.jogamp.common.nio.Buffers.newDirectFloatBuffer(Buffers.java:115)
        at com.jogamp.opencl.CLContext.createFloatBuffer(CLContext.java:316)

Apparently the float buffer will instantiate a byte buffer, i.e. the length for the byte buffer is now multiplied by 4.
I guess this results in an overflow of the integer array indexing because 2^29*4 = 2^31, which is already considered to be a negative number!
This effectively limits the CLMemory usage to < 2GB for a single float buffer. If float could be indexed directly, the range would be extended to < 8GB. We are working in the field of medical image processing where we are dealing with large volumes of up to 1024^3 = 2^30 float values just in case one might wonder why we would need such large linear data arrays.

Is there a known solution to this problem? Or can you give me a hint on how to implement a workaround for such large arrays?

Thanks
Martin