4 ms·

This reminds me of a story I once heard about shipbuilding during WW2. Supposedly, although designs and blueprints were made in great detail, following them tod

This reminds me of a story I once heard about shipbuilding during WW2. Supposedly, although designs and blueprints were made in great detail, following them today wouldn't give working ships, because the workers implementing them at the time saw where the designs wouldn't work and fixed them of their own initiative. In a way, the opposite of today's optimizing compilers.

ido 6y ago
JIT optimization?
- WalterBright 6y ago
  There have been some regressions in the D compiler due to not documenting the "why" of some things in the code, that a later person unwound.
pjc50 6y ago
This was part of what got the RAF Nimrod programme eventually cancelled; they were ancient airframes that required an ongoing supply of spare parts, but as you describe building parts from the original plans didn't fit properly.
- KineticLensman 6y ago
  Yes, each airframe was essentially a completely different aircraft, although each was notionally built from the same plans. Bids for upgrades that were generated against a single reference airframe went massively over budget when executed because no two planes were the same. The other thing that got the programme cancelled was the crash of Nimrod MR2 Aircraft XV230 in Afghanistan in 2006, as described in exhaustive detail in the Haddon Cave report [0 - pdf]. Part of the cause was design flaws introduced over years of updates, that interacted with each other fatally. [0] https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/229037/1025.pdf https://assets.publishing.service.gov.uk/government/uploads/...
rcxdude 6y ago
This happens all the time when you get stuff made. It's generally good and useful, but the real challenge is in getting these changes documented, and getting the changes verified against the original specification. The Hyatt Regency walkway collapse was a good example of this going wrong: while the original design was flawed, the fact that it wasn't easily manufactured meant it then got modified, and even though the builder discussed the changes with the designers, the designers did not check that their original calculations still applied and as a result the structure was substantially weakened and collapsed. Also, making sure this process for exists and is documented precisely is one of the reasons medical devices are so expensive. https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse
WalterBright 6y ago
That's also true of WW2 aircraft. Drawings exist for, say, the P-51, but you can't build the airplane from the drawings because the drawings were made after the fact. The real design was the tooling and mechanics.

ido 6y ago

JIT optimization?

WalterBright 6y ago
There have been some regressions in the D compiler due to not documenting the "why" of some things in the code, that a later person unwound.

pjc50 6y ago

This was part of what got the RAF Nimrod programme eventually cancelled; they were ancient airframes that required an ongoing supply of spare parts, but as you describe building parts from the original plans didn't fit properly.

KineticLensman 6y ago
Yes, each airframe was essentially a completely different aircraft, although each was notionally built from the same plans. Bids for upgrades that were generated against a single reference airframe went massively over budget when executed because no two planes were the same. The other thing that got the programme cancelled was the crash of Nimrod MR2 Aircraft XV230 in Afghanistan in 2006, as described in exhaustive detail in the Haddon Cave report [0 - pdf]. Part of the cause was design flaws introduced over years of updates, that interacted with each other fatally. [0] https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/229037/1025.pdf https://assets.publishing.service.gov.uk/government/uploads/...

rcxdude 6y ago

This happens all the time when you get stuff made. It's generally good and useful, but the real challenge is in getting these changes documented, and getting the changes verified against the original specification. The Hyatt Regency walkway collapse was a good example of this going wrong: while the original design was flawed, the fact that it wasn't easily manufactured meant it then got modified, and even though the builder discussed the changes with the designers, the designers did not check that their original calculations still applied and as a result the structure was substantially weakened and collapsed. Also, making sure this process for exists and is documented precisely is one of the reasons medical devices are so expensive. https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse

WalterBright 6y ago

That's also true of WW2 aircraft. Drawings exist for, say, the P-51, but you can't build the airplane from the drawings because the drawings were made after the fact. The real design was the tooling and mechanics.