printf buffer

[drsn00ker]

Complete noob here, but I have found your wrapper particularly useful to accomplish tasks way passed my skill level.
My latest project sadly fails because it maxes out the device printf buffer. If I could change it to 80Mb I would be a happy camper. Alternatively if I could flush it from within the kernel I'd be in business as well.
I'm using an AMD 7900XTX (win10).

Google doesn't show an obvious answer and the AI completely makes up a non-exiting environmental variable....
(AMD_OCL_PRINTF_BUFFER_SIZE)

[ProjectPhysX]

Hi @drsn00ker,

The printf needs a bit of a hack to work within the R() stringification macro:

	float x = 1.23f;
	if(get_global_id(0)==0) )+ "printf(\"Hello\tWorld\t%f\\n\",x);" +R(

• the condition if(get_global_id(0)==0) ensures that the printf is not spammed by a gazillion GPU threads <-- not having such a condition this is likely your issue with printf buffer overflow
• with the )+ you exit the stringification macro, and later enter it again with a +R(
• in between you place the "printf(...,x);" packaged as a normal string literal
• the string within the printf itself must be escaped with a \", must not contain any spaces (but tab \t works), and the \\n for newline must be double-escaped with two \\

Kind regards,
Moritz

[drsn00ker]

Thanks for your reply. Sadly that's not my problem. I'm trying to bruteforce a parameter space of 100T and a quick (15hr) cut knocks it down to several 100k. I do this cut using your wrapper and just printf the possible solutions (strings). Then I use a secondary program to perform the much more difficult (and slower) sort through the 100k remaining possibilities as a text file to find to correct solution.
An alternative would be to be able to return a string from the kernel to main, but based on my reading and current skills that's also a few bridges too far.

Does the \n act as a buffer flush? printf with \n works properly for me to terminate the current line.

[ProjectPhysX]

Hi @drsn00ker,

printf is meant as a debugging tool, not to output the results of the kernel.
Write the kernel's output into a global buffer.

Kind regards,
Moritz

[drsn00ker]

Okay, I'll try to figure out how to create and use a global buffer.
Thanks!