Windows Simple Batch "Multithread" Processing - multithreading

Question

Hi I am pushed by deadlines, so I will post my question here as I go along with my search..here is my script, all it does is look at every file of a folder, and create different "list.txt" depending of the value of "tree_size.txt" formated as CSV.txt (filename,size):
FOR %%I in (%inputDir%\*.*) DO (
FOR /F "tokens=1,2" %%A IN (%tree_size%) DO (
IF %%~nxI==%%A IF %%B LEQ 10.000 (
echo %%~dpnxI >> %inputDir%\0_10.txt)
IF %%~nxI==%%A IF %%B GTR 10.000 IF %%B LEQ 25.000 (
echo %%~dpnxI >> %inputDir%\11_25.txt)
IF %%~nxI==%%A IF %%B GTR 25.000 IF %%B LEQ 40.000 (
echo %%~dpnxI >> %inputDir%\26_40.txt)
IF %%~nxI==%%A IF %%B GTR 40.000 IF %%B LEQ 55.000 (
echo %%~dpnxI >> %inputDir%\41_55.txt)
IF %%~nxI==%%A IF %%B GTR 55.000 (
echo %%~dpnxI >> %inputDir%\56_plus.txt)
)
)
My aim is to modify this code in order to use multithread processing, which seams to be an option using batch scripting on Windows 7.

Answer 1

Your problem is one of approach.
As you have 50,000 files and assuming you have 50,000 lines in your tree_size file (of which you've not given us a sample) then you are reading tree_size 50,000 times and executing the if tree 50,000 * 50,000 = 2,500,000,000 times. Each of your comparison blocks makes 5 tests each time = 12,500,000,000 tests.
Try this:
FOR /F "tokens=1,2" %%A IN (%tree_size%) DO if exist "%inputDir%\%%A" (
IF %%B LEQ 10.000 (
echo %inputDir%\%%A >> %inputDir%\0_10.txt
) else (
IF %%B LEQ 25.000 (
echo %inputDir%\%%A >> %inputDir%\11_25.txt
) else (
IF %%B LEQ 40.000 (
echo %inputDir%\%%A >> %inputDir%\26_40.txt
) else (
IF %%B LEQ 55.000 (
echo %inputDir%\%%A >> %inputDir%\41_55.txt
) else (
echo %inputDir%\%%A >> %inputDir%\56_plus.txt
)))))
)
which should accomplish the same thing using only 50,000 cycles of the inner loop.