help2002

It's UWAweek 49

help2002

This forum is provided to promote discussion amongst students enrolled in CITS2002 Systems Programming.
Please consider offering answers and suggestions to help other students! And if you fix a problem by following a suggestion here, it would be great if other interested students could see a short "Great, fixed it!" followup message.

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UWA week 36 (2nd semester, mid-semester break) ↓

1st project New Sample Solution Bug? (maybe) (all 3)

11:35am Mon 4th Sep, ANONYMOUS

Ok so if I try using the new sample solution with a command file containing only the default "cal" command, and syscall file directly copied from project page. The verbose output shows the write being completed instantly with negative time? Not sure if I wrote something wrong, apologies if it was my mistake. Supposedly the write time would be 2000/3 usecs (about 666.67usecs)

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1st project New Sample Solution Bug? (maybe) (all 3)

2:43pm Mon 4th Sep, Christopher M.

ANONYMOUS wrote:

> Ok so if I try using the new sample solution with a command file containing only the default "cal" command, and syscall file directly copied from project page. The verbose output shows the write being completed instantly with negative time?

Thanks! Yes, very likely a bug through only testing with too-small values. A negative time quickly suggests a problem with overflow in the calculation of time required. Will look into it.

1st project New Sample Solution Bug? (maybe) (all 3)

3:57am Wed 6th Sep, Christopher M.

I believe the problem reporting negative I/O times has been corrected. Please report any problems. The arithmetic was being performed using a standard int (4 bytes), which overflowed with larger (faster) I/O speeds. If you're having similar problems, you can perform the arithmetic using int64_t or double. You may like to read about the ceil() function, too.