9 ms·

Tonight at 9: Surprising doomsayers, the market worked again!

by mwint 4y ago

mindslight 4y ago
If you ever rent a truck/trailer, please have someone else load it. Wild oscillation is not desirable behavior. https://www.youtube.com/watch?v=6mW_gzdh6to https://www.youtube.com/watch?v=6mW_gzdh6to
- mwint 4y ago
  I mean, I have probably loaded and driven heavier loads than you have. This analogy is about as strained as it gets.
  - mindslight 4y ago
    Perhaps. It wasn't an analogy, but rather a vibrant reference to the concept of oscillation. Your original comment declares a simplistic version of "working" based around having reached one specific condition, while writing off the dynamic system behavior and other effects that occurred while getting to this point. Now, do we have reasons to be believe that this oscillation between shortage and surplus will grow or diminish? Will the next half-cycle of the oscillation create negative qualitative effects, even if it is ultimately diminishing? I'm not saying there are easy answers to those questions, but we're better off being able to ask them.
    - mwint 4y ago
      Maybe we can ask a related question: How can we profit from these oscillations? If they're predictable, there should be an arbitrage opportunity.
      - MrMan 4y ago
        I just bought a shipping container so I am doing my part
        deleted 4y ago
        [deleted]
      - heavenlyblue 4y ago
        How about you suggest an actual business plan than an abstract idea?
      - losteric 4y ago
        Doesn't arbitrage reflect pricing inefficiency? What is inefficient in container pricing? I can certainly see opportunity to profit through stock market inefficiencies. Eg transportation stocks that were overpriced on supply chain FUD
      - toast0 4y ago
        The way to profit from gluts and squeezes is to warehouse products. Warehousing perishable products is much harder. If you store the products in containers, it's easier to ship them when there's a squeeze, and you're also warehousing containers ;) Of course, the more people who buy the glut and sell the squeeze, the less of a glut and a squeeze there is.
        bertjk 4y ago
        Of course, if you do warehouse products, and then try to take advantage of a squeeze, then you may get accused of price gouging.
  - deleted 4y ago
    [deleted]
- an_taeus 4y ago
  The actionable advice here is if you're loading a trailer, you want weight / center of gravity as close to the front / cab as possible. If loading, y'know, 40,000 lbs for a tractor trailer and you're loading it with pallets, alternate the pallet rows as far to the left and right as possible, switching direction every row. This prevents tipping and also does a favor to the person who has to unload it at the destination as it prevents weird slippages of pallet orientation and crunching. Poorly loaded trailers can definitely kill the trucker and other drivers. The oscillation severity really depends on the spread between the greatest and least weight of the items going into the trailer.
sudosysgen 4y ago
Taking multiple years to correct a critical shortage and then overcorrecting is not a good example of markets being efficient. Any kind of system that responds to usage can do this, the criteria is about speed of correction, lack of oscillation, and avoidance of side effects.
- Doxin 4y ago
  It's clear, We need a PID controller running the markets. Only half joking.
  - carlmr 4y ago
    Maybe we are doing PID, but we need anti-windup.
    - infogulch 4y ago
      I wasn't familiar with anti-windup, so I found https://www.scilab.org/pid-anti-windup-schemes https://www.scilab.org/pid-anti-windup-schemes that seems to cover the concept reasonably well. One thing I noticed is that smoothing functions that reduce overshooting the response also add some delay to the time taken to first reach the command threshold. This is interesting, if not quite surprising.
      - carlmr 4y ago
        >I wasn't familiar with anti-windup, so I found https://www.scilab.org/pid-anti-windup-schemes https://www.scilab.org/pid-anti-windup-schemes that seems to cover the concept reasonably well. It's one of the fundamental techniques to get PIDs to work properly IRL. I can't find it right now, but I remember having a cheat sheet with a lot of tricks to make PIDs work properly. As a control engineer you learn a lot of fancy techniques, of which you usually only use a few, but practical PID control is sadly not taught in most courses because it's basically a collection of hacks. If you know a little bit more about the system's behavior you can usually precalculate the optimal inputs and use the PID only for course correction, that often yields much better responses than what you can achieve with a controller alone. If your system is nonlinear, it might be useful to use gain scheduling to adapt the PID parameters to the setpoint region you're operating in. Switching behaviors in the system can also mess up your responses. Sometimes your system has a vibrating frequency that can lead to resonance in your control. You may need to filter that, too, maybe even with a sliding frequency window. E.g. when controlling a gearbox attached to a motor, you don't want to actuate at the motor's vibrating frequency. >smoothing functions that reduce overshooting the response also add some delay to the time taken It's not so surprising if you think about what a low pass filter does. By filtering out the high frequencies the response becomes more sluggish, meaning that your input to the PID is already delayed. This means your PID reacts more slowly.

Tonight at 9: Surprising doomsayers, the market worked again!

by mwint 4y ago

Tonight at 9: Surprising doomsayers, the market worked again!

If you ever rent a truck/trailer, please have someone else load it. Wild oscillation is not desirable behavior. https://www.youtube.com/watch?v=6mW_gzdh6to https://www.youtube.com/watch?v=6mW_gzdh6to

mwint 4y ago
I mean, I have probably loaded and driven heavier loads than you have. This analogy is about as strained as it gets.
- mindslight 4y ago
  Perhaps. It wasn't an analogy, but rather a vibrant reference to the concept of oscillation. Your original comment declares a simplistic version of "working" based around having reached one specific condition, while writing off the dynamic system behavior and other effects that occurred while getting to this point. Now, do we have reasons to be believe that this oscillation between shortage and surplus will grow or diminish? Will the next half-cycle of the oscillation create negative qualitative effects, even if it is ultimately diminishing? I'm not saying there are easy answers to those questions, but we're better off being able to ask them.
  - mwint 4y ago
    Maybe we can ask a related question: How can we profit from these oscillations? If they're predictable, there should be an arbitrage opportunity.
    - MrMan 4y ago
      I just bought a shipping container so I am doing my part
      - deleted 4y ago
        [deleted]
    - heavenlyblue 4y ago
      How about you suggest an actual business plan than an abstract idea?
    - losteric 4y ago
      Doesn't arbitrage reflect pricing inefficiency? What is inefficient in container pricing? I can certainly see opportunity to profit through stock market inefficiencies. Eg transportation stocks that were overpriced on supply chain FUD
    - toast0 4y ago
      The way to profit from gluts and squeezes is to warehouse products. Warehousing perishable products is much harder. If you store the products in containers, it's easier to ship them when there's a squeeze, and you're also warehousing containers ;) Of course, the more people who buy the glut and sell the squeeze, the less of a glut and a squeeze there is.
      - bertjk 4y ago
        Of course, if you do warehouse products, and then try to take advantage of a squeeze, then you may get accused of price gouging.
- deleted 4y ago
  [deleted]
an_taeus 4y ago
The actionable advice here is if you're loading a trailer, you want weight / center of gravity as close to the front / cab as possible. If loading, y'know, 40,000 lbs for a tractor trailer and you're loading it with pallets, alternate the pallet rows as far to the left and right as possible, switching direction every row. This prevents tipping and also does a favor to the person who has to unload it at the destination as it prevents weird slippages of pallet orientation and crunching. Poorly loaded trailers can definitely kill the trucker and other drivers. The oscillation severity really depends on the spread between the greatest and least weight of the items going into the trailer.

sudosysgen 4y ago

Taking multiple years to correct a critical shortage and then overcorrecting is not a good example of markets being efficient. Any kind of system that responds to usage can do this, the criteria is about speed of correction, lack of oscillation, and avoidance of side effects.

Doxin 4y ago
It's clear, We need a PID controller running the markets. Only half joking.
- carlmr 4y ago
  Maybe we are doing PID, but we need anti-windup.
  - infogulch 4y ago
    I wasn't familiar with anti-windup, so I found https://www.scilab.org/pid-anti-windup-schemes https://www.scilab.org/pid-anti-windup-schemes that seems to cover the concept reasonably well. One thing I noticed is that smoothing functions that reduce overshooting the response also add some delay to the time taken to first reach the command threshold. This is interesting, if not quite surprising.
    - carlmr 4y ago
      >I wasn't familiar with anti-windup, so I found https://www.scilab.org/pid-anti-windup-schemes https://www.scilab.org/pid-anti-windup-schemes that seems to cover the concept reasonably well. It's one of the fundamental techniques to get PIDs to work properly IRL. I can't find it right now, but I remember having a cheat sheet with a lot of tricks to make PIDs work properly. As a control engineer you learn a lot of fancy techniques, of which you usually only use a few, but practical PID control is sadly not taught in most courses because it's basically a collection of hacks. If you know a little bit more about the system's behavior you can usually precalculate the optimal inputs and use the PID only for course correction, that often yields much better responses than what you can achieve with a controller alone. If your system is nonlinear, it might be useful to use gain scheduling to adapt the PID parameters to the setpoint region you're operating in. Switching behaviors in the system can also mess up your responses. Sometimes your system has a vibrating frequency that can lead to resonance in your control. You may need to filter that, too, maybe even with a sliding frequency window. E.g. when controlling a gearbox attached to a motor, you don't want to actuate at the motor's vibrating frequency. >smoothing functions that reduce overshooting the response also add some delay to the time taken It's not so surprising if you think about what a low pass filter does. By filtering out the high frequencies the response becomes more sluggish, meaning that your input to the PID is already delayed. This means your PID reacts more slowly.