tclmeelmo (u/tclmeelmo)

tclmeelmo commented on Tesla Model S autonomously crashes into a parked trailer while in ‘summon’ mode theverge.com/2016/5/11/11... · Posted by u/davidiach

mikeash · 10 years ago

The lip isn't detected by the sensors. The car stops on it when the tires hit it because of the physical obstacle it presents and the extra force needed to climb it.

It's weird, usually the car actually passed over the lip with the front tires, but then stopped when the rear tires got to it. The threshold for stopping must be very close to what it actually encounters there.

tclmeelmo · 10 years ago

Someone on Youtube had what I thought was a clever solution: a piece of trim (looked like shoe molding) to bridge the 1" step. Cheap, and they claimed 100% effective.

tclmeelmo commented on Don’t invert that matrix (2010) johndcook.com/blog/2010/0... · Posted by u/egjerlow

jacobolus · 10 years ago

For example, you factorize A into LU, so that you have LUx = b.

Now you can let Ux = y, solve the system Ly = b for y, then solve Ux = y for x.

Solving each triangular system is fast: O(n^2).

If you need to do this with a different b, you can do it again, and you already have A factorized, which was the expensive part, i.e. O(n^3).

(Depending on the type of problem, you might want to factorize the original matrix in a different way, e.g. QR or Cholesky or whatever.)

tclmeelmo · 10 years ago

IIRC, the HP-15C used LU decomposition in its matrix math routines.

tclmeelmo commented on Tesla Model S autonomously crashes into a parked trailer while in ‘summon’ mode theverge.com/2016/5/11/11... · Posted by u/davidiach

mikeash · 10 years ago

I see a lot of comments about safety here. Note that Tesla's Summon mode limits the car to 1MPH and 39ft of movement. It also is very sensitive to resistance, to the point that I actually had to construct ramps for my car to climb the 1-inch lip at the entrance to my garage, otherwise it would stop at that point and refuse to go further. Using this feature to kill somebody is going to take a lot of effort. There are many interesting discussions to be had here about software, UX, corporate responsibility in the face of user error with bad UX, etc., but I don't think there's much room to discuss safety here. This is a risk to property, not life.

tclmeelmo · 10 years ago

> It also is very sensitive to resistance, to the point that I actually had to construct ramps for my car to climb the 1-inch lip at the entrance to my garage, otherwise it would stop at that point and refuse to go further.

The pictures of the car in a article linked elsewhere in this discussion (https://www.ksl.com/?sid=39727592&nid=148&title=utah-man-say...) show that the windshield was smashed. I'm finding it challenging to reconcile your personal example with the images of the smashed windshield; in my own experience, it takes some effort to break laminated safety glass. I would think (perhaps wrongly) that it would take more effort to break safety glass than would be stopped by a 1in. step.

> but I don't think there's much room to discuss safety here.

I couldn't disagree more. I don't understand why it should be possible to disable any safety interlock (at least, that's how I'm interpreting the feature description) in a consumer product, especially persistently.

tclmeelmo commented on Tesla Model S autonomously crashes into a parked trailer while in ‘summon’ mode theverge.com/2016/5/11/11... · Posted by u/davidiach

kylec · 10 years ago

Is it possible that those safeguards were deactivated by the Tesla delivery specialist, or by the customer at the suggestion of the delivery specialist, in order to demonstrate how the feature works? I genuinely don't know if that's something the delivery specialists do, but I think it's plausible. Tesla demonstrates Autopilot on test drives as a matter of course, and I could easily see them wanting to demonstrate Summon to new customers.

If so, I think it's possible the customer was not made aware of the safety implications and limitations of the system.

tclmeelmo · 10 years ago

It would also seem possible for a spouse or other alternate driver of the car to have disabled those safeguards.

tclmeelmo commented on Tesla Model S autonomously crashes into a parked trailer while in ‘summon’ mode theverge.com/2016/5/11/11... · Posted by u/davidiach

tclmeelmo · 10 years ago

This feature has me wondering what the SAE standards for automatic transmissions have to say on the matter, if anything?

I'm not familiar with them, nor do I have access, but I'm hoping someone here might be helpful on either aspect. Specifically, I'm wondering if the standards for automatic transmission controls recommend against having the Park setting do anything beyond activating the parking pawl and parking brake (when electronically controlled).

tclmeelmo commented on A Marriage Gone Bad: Walgreens Struggles to Shake Off Theranos nytimes.com/2016/04/22/bu... · Posted by u/dbcooper

a3n · 10 years ago

And were these experienced investors? :)

tclmeelmo · 10 years ago

I am under the impression that they were experienced in IT but inexperienced in biomedical investments.