5 ms·

Analog (or analogue) computers have their uses, however, in my experience, with analogue electronic computers, they have many problems: - limited dynamic range

Analog (or analogue) computers have their uses, however, in my experience, with analogue electronic computers, they have many problems: - limited dynamic range of perhaps 30dB (1000) - it is easy to saturate a signal (there is no overflow bit) - oscillations are easy to induce, but once again hard to detect, especially in a circuit in the middle of a calculation chain - noise gets amplified across the system

JKCalhoun 9y ago
Reminded me of A.K. Dewdney's "Computer Recreations" column in "Scientific American" back in the day (I think a lot of people may have hated on his column since it followed in the shadow of Martin Gardener's infamous "Mathematical Recreations"). One of the "analog computers" he mentioned was using dried spaghetti to sort numbers — where the length of each spaghetti noodle represented the magnitude of a number. Of course grabbing them into a bundle in your hand and setting the bundle on end on a flat surface would "sort" the values. Would the surface tension across a film that accurately finds the shortest path between n points be considered a "computation"? One thing fascinating by "analog computers" is the way they seem to be practically instantaneous regardless of n. That is perhaps part of the efficiency reflected in the article.
- kybernetikos 9y ago
  > One thing fascinating by "analog computers" is the way they seem to be practically instantaneous regardless of n. That is perhaps part of the efficiency reflected in the article. If this were true, it would have profound implications. It's probably not true. http://www.scottaaronson.com/papers/npcomplete.pdf http://www.scottaaronson.com/papers/npcomplete.pdf
  - rhaps0dy 9y ago
    It's "true". The catch is that the analog computer's circuit size (which is analog to the digital computer's time) has to scale with n.
    - prestonbriggs 9y ago
      But it's not true - the interesting components (the op amps, multipliers, etc) all have bandwidth limitations.
  - VLM 9y ago
    His soap bubble analogy is pretty cool. There is a direct analogy for filtering where its impossible to get instantaneous perfect response out of a filter, either DSP simulated or hardware. It would seem that merely filtering a signal is much simpler than simulating the airflow across a wing or whatever. There are also conceptual issues that the airflow across a wing is ideally under stable low angles of attack, constant, but during "fun times" which is precisely when you'd want a model instead of a test pilot, the air flow will vary over time (to the general detriment of flying ability...) so what it means to instantly solve a wing is unclear in itself.
- pmontra 9y ago
  I remember that article. This is Spaghetti Sort from Wikipedia https://en.m.wikipedia.org/wiki/Spaghetti_sort https://en.m.wikipedia.org/wiki/Spaghetti_sort

JKCalhoun 9y ago

Reminded me of A.K. Dewdney's "Computer Recreations" column in "Scientific American" back in the day (I think a lot of people may have hated on his column since it followed in the shadow of Martin Gardener's infamous "Mathematical Recreations"). One of the "analog computers" he mentioned was using dried spaghetti to sort numbers — where the length of each spaghetti noodle represented the magnitude of a number. Of course grabbing them into a bundle in your hand and setting the bundle on end on a flat surface would "sort" the values. Would the surface tension across a film that accurately finds the shortest path between n points be considered a "computation"? One thing fascinating by "analog computers" is the way they seem to be practically instantaneous regardless of n. That is perhaps part of the efficiency reflected in the article.

kybernetikos 9y ago
> One thing fascinating by "analog computers" is the way they seem to be practically instantaneous regardless of n. That is perhaps part of the efficiency reflected in the article. If this were true, it would have profound implications. It's probably not true. http://www.scottaaronson.com/papers/npcomplete.pdf http://www.scottaaronson.com/papers/npcomplete.pdf
- rhaps0dy 9y ago
  It's "true". The catch is that the analog computer's circuit size (which is analog to the digital computer's time) has to scale with n.
  - prestonbriggs 9y ago
    But it's not true - the interesting components (the op amps, multipliers, etc) all have bandwidth limitations.
- VLM 9y ago
  His soap bubble analogy is pretty cool. There is a direct analogy for filtering where its impossible to get instantaneous perfect response out of a filter, either DSP simulated or hardware. It would seem that merely filtering a signal is much simpler than simulating the airflow across a wing or whatever. There are also conceptual issues that the airflow across a wing is ideally under stable low angles of attack, constant, but during "fun times" which is precisely when you'd want a model instead of a test pilot, the air flow will vary over time (to the general detriment of flying ability...) so what it means to instantly solve a wing is unclear in itself.
pmontra 9y ago
I remember that article. This is Spaghetti Sort from Wikipedia https://en.m.wikipedia.org/wiki/Spaghetti_sort https://en.m.wikipedia.org/wiki/Spaghetti_sort