包含pyCuda时，shell_exec的输出不再返回到PHP

Question

I am calling this python file:

import sys
if __name__ == "__main__":
    print sys.argv[1]

From PHP like this:

$param = "hello";
$result = shell_exec("python /path/to/python/file.py " . $param);
echo $result;

Which works great as hello is displayed when running the PHP file. However, when I import pyCuda (2012.1) into the python file, the output is no longer returned to PHP even though it is still shown when running the command from bash. This is the python file with pyCuda imported:

from pycuda import driver as drv
from pycuda import tools
from pycuda import autoinit
import sys
if __name__ == "__main__":
    print sys.argv[1]

Why does PHP no longer receive the output when pyCuda is imported and what is the best way to read the output from this python file in PHP?

Many thanks!

Answer 1

pycuda.autoinit registers an atexit autohandler to clean up the CUDA context it creates so that the python code exits gracefully. It is likely that this is terminating the application without flushing stdout, so the output never gets emitted.

So either try explicit flushing of stdout:

import sys
print sys.argv[1]
sys.stdout.flush()

or don't use pycuda.autoinit and handle setup and pull down of the driver API context yourself.