4 ms·

Considering scientific statistics, which says there are 0.5 to 25 bugs per KLoC in delivered software, we are really lucky that stuff still work... :D

red75prime 9y ago
Corner cases. Relatively rare until exploited.
AceJohnny2 9y ago
I use the following metaphor: software is like a narrow path high up on the arete of a mountain, with thousand-foot drops on either side. Your goal is to walk down that path. If everything goes well (all the input is as expected), you'll walk the path straight and reach your goal. Bad software (most of it, honestly) has no guardrails: do something wrong, take one step to the side, and you fall crashing off the narrow path. Robust software has guardrails, handles all the error conditions, to make sure you stay on the path (or at least return to the start). Most software is tested against expected input. It's already a lot of work to get things working for the expected case, it's usually enough to stop there. Make the path, expect smart hikers, omit guardrails. This is why stuff still works: most of the time, things go as expected. It is a huge investment to test against all error conditions. I only know of the Space Shuttle that had the robustness requirements to shoulder the cost of implementing that. As I recall, their conventional productivity metrics were abysmal (<1 LoC/day/engineer?), but it was robust. I've worked on High-Availability equipment. The software quality wasn't better than elsewhere, but the recovery mechanisms were much better. For example, all mission-critical data was mirrored to redundant HW/SW, and there was a standby system ready to pick up whenever the active copy crashed... which wasn't too often, but it happened. This is similar to Netflix' "Chaos Monkey" approach to software design.
kurtisc 9y ago
Assuming 0.5 rounds down, that seems like an essentially useless statistic. If you deliver a randomised binary that just doesn't run, does that count as more than one bug?
- colejohnson66 9y ago
  0.5 rounds up though...
  - kurtisc 9y ago
    Only for 2/5 IEEE 754 rounding methods! What's 0.5 of a bug, anyway?
    - dsr_ 9y ago
      A full bug, but it takes two thousand lines of code to surface.
    - cjsuk 9y ago
      A feature!

red75prime 9y ago

Corner cases. Relatively rare until exploited.

AceJohnny2 9y ago

I use the following metaphor: software is like a narrow path high up on the arete of a mountain, with thousand-foot drops on either side. Your goal is to walk down that path. If everything goes well (all the input is as expected), you'll walk the path straight and reach your goal. Bad software (most of it, honestly) has no guardrails: do something wrong, take one step to the side, and you fall crashing off the narrow path. Robust software has guardrails, handles all the error conditions, to make sure you stay on the path (or at least return to the start). Most software is tested against expected input. It's already a lot of work to get things working for the expected case, it's usually enough to stop there. Make the path, expect smart hikers, omit guardrails. This is why stuff still works: most of the time, things go as expected. It is a huge investment to test against all error conditions. I only know of the Space Shuttle that had the robustness requirements to shoulder the cost of implementing that. As I recall, their conventional productivity metrics were abysmal (<1 LoC/day/engineer?), but it was robust. I've worked on High-Availability equipment. The software quality wasn't better than elsewhere, but the recovery mechanisms were much better. For example, all mission-critical data was mirrored to redundant HW/SW, and there was a standby system ready to pick up whenever the active copy crashed... which wasn't too often, but it happened. This is similar to Netflix' "Chaos Monkey" approach to software design.

kurtisc 9y ago

Assuming 0.5 rounds down, that seems like an essentially useless statistic. If you deliver a randomised binary that just doesn't run, does that count as more than one bug?

colejohnson66 9y ago
0.5 rounds up though...
- kurtisc 9y ago
  Only for 2/5 IEEE 754 rounding methods! What's 0.5 of a bug, anyway?
  - dsr_ 9y ago
    A full bug, but it takes two thousand lines of code to surface.
  - cjsuk 9y ago
    A feature!