maikonadams / opencl-book-samples

Automatically exported from code.google.com/p/opencl-book-samples
0 stars 0 forks source link

Ch. 7, p. 251 buffer length & type mistake #79

Open GoogleCodeExporter opened 8 years ago

GoogleCodeExporter commented 8 years ago
Is this errata for the book or an issue with the source code?
Book and source.

Chapter 7, Section: Creating Buffers and Sub-Buffers, page: 251

Book:

Performing square kernel by many devices requires passing subsequent parts of 
buffer to clEnqueueNDRangeKernel() which is done with offset. But created 
buffer can contain only NUM_BUFFER_ELEMENTS elements and offset,  calculated to 
be multiple of that size, for subsequent devices is out of the range of the 
buffer.

Size of buffer should be calculated as:
sizeof(float) * NUM_BUFFER_ELEMENTS * number_of_devices

Source:

In loop:
// Submit kernel enqueue to each queue
for (int i = 0; i < queues.size(); i++)
...
size_t offset = i * NUM_BUFFER_ELEMENTS * sizeof(int);
...

Offset should be calculated with 'sizeof(float)' instead of 'sizeof(int)', 
because float * inputOutput is passed to: 'buffer = clCreateBuffer(...)'.

Original issue reported on code.google.com by eqo...@gmail.com on 12 Dec 2013 at 3:05