OpenACC on K20 - max data chunk size

Accelerated Computing HPC Compilers Legacy PGI Compilers
1

I’m a graduating student involved in a performance analysis of a scientific application that I’m porting to OpenACC (I’m using PGI 14.1).

In some tests, I noticed that (thanks to NVPP) maximum chunk size of data transferred to device is 16 MB.

Is this an arch-dependent value? The device is a Kepler20s

Thanks in advance.

Paolo L.

2

Paolo,

The chunk size can be adjusted via an environment variable: PGI_ACC_BUFFERSIZE.

For example, if you wish to use a 32 MB buffer size, you could do the following in bash:

export PGI_ACC_BUFFERSIZE=32M

Hope this helps.

Best regards,

+chris

3

Thank you Chris, this is exactly what I need.

Have a nice day.

Paolo