fubarobfusco comments on PZ Myers on the Infeasibility of Whole Brain Emulation - Less Wrong

11 Post author: peter_hurford 14 July 2012 06:13PM

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Comment author: fubarobfusco 14 July 2012 07:45:31PM *  17 points [-]

Computer folk often use the terms emulation and simulation to mean two different things, which Myers appears to be conflating. In the sense I'm thinking of, simulation means modeling the components of a system at a relatively low level — such as all the transistors and connections in a CPU — whereas emulation means replicating the functional behavior of a system.

(Of course, these terms are used in a lot of other ways, too. SimCity is neither a simulation nor an emulation in the sense I'm using.)

For instance, a circuit simulator modeling a piece of RAM might keep track of the amount of charge in a particular capacitor that represents a particular bit in memory; but an emulator would just keep track of what numerical value was stored in which addressable location. An emulator doesn't attempt to replicate how the original system works, but rather what it does.

(A non-computational analogy: An artificial heart doesn't duplicate the muscle cells of a natural heart; it duplicates the function of a heart, namely moving blood around. It's not necessary to copy the behavior of each individual muscle cell — to say nothing of each molecule in each muscle cell! — in order to duplicate the function of a heart well enough to keep a person alive for years.)

From what I've read, folks who expect WBE don't expect modeling at the molecular level (a simulation of a brain), but rather at some higher functional level (an emulation, hence the term), so much as that some sort of functional components — maybe individual neurons; maybe specific brain regions — can be emulated without simulating them.

Comment author: Kaj_Sotala 15 July 2012 07:42:37AM *  7 points [-]

In the sense I'm thinking of, simulation means modeling the components of a system at a relatively low level — such as all the transistors and connections in a CPU — whereas emulation means replicating the functional behavior of a system.

There seems to be conflicting usage about this.

http://www.fhi.ox.ac.uk/__data/assets/pdf_file/0019/3853/brain-emulation-roadmap-report.pdf

The term emulation originates in computer science, where it denotes mimicking the function of a program or computer hardware by having its low‐level functions simulated by another program. While a simulation mimics the outward results, an emulation mimics the internal causal dynamics (at some suitable level of description). The emulation is regarded as successful if the emulated system produces the same outward behaviour and results as the original (possibly with a speed difference). This is somewhat softer than a strict mathematical definition1. [...]

By analogy with a software emulator, we can say that a brain emulator is software (and possibly dedicated non‐brain hardware) that models the states and functional dynamics of a brain at a relatively fine‐grained level of detail.

In particular, a mind emulation is a brain emulator that is detailed and correct enough to produce the phenomenological effects of a mind.

https://secure.wikimedia.org/wikipedia/en/wiki/Emulation

The word emulation refers to: [...]

The low-level simulation of equipment or phenomena by artificial means, such as by software modeling. Note that simulation may also allow an abstract high-level model.

On the other hand, the top-voted answer at http://stackoverflow.com/questions/1584617/simulator-or-emulator-what-is-the-difference says that

Emulation is the process of mimicking the outwardly observable behavior to match an existing target. The internal state of the emulation mechanism does not have to accurately reflect the internal state of the target which it is emulating.

Simulation, on the other hand, involves modeling the underlying state of the target. The end result of a good simulation is that the simulation model will emulate the target which it is simulating.

Comment author: [deleted] 14 July 2012 11:06:59PM 3 points [-]

Well, when I argued on here last week ( http://lesswrong.com/lw/d80/malthusian_copying_mass_death_of_unhappy/6y2r?context=1#6y2r ) that emulation would be more difficult than people imagine, based on my experience of working on software that does that, people downvoted it and argued "no, people aren't talking about emulation, but about modelling at the molecular level"

Comment author: fubarobfusco 14 July 2012 11:35:35PM *  5 points [-]

Hmm ... from my reading of that conversation, one person said that.

Comment author: [deleted] 15 July 2012 05:38:15PM 3 points [-]

Fair enough, although multiple people downvoted that comment (it seems to have had some upvotes since to compensate). Even if they downvoted for different reasons though, that's still at least one counterexample of someone who fits into the category "folks who expect WBE".

Emulation without simulation would require not only vastly more understanding of the brain and of cell biology than we have now (most of the problems Myers points out would still be there, though not all) but on top of that all the problems you hit when trying to emulate one system on another, plus a whole lot of problems no-one's ever even conceived because no-one's ever ported an algorithm (for which we have neither source code nor documentation) from a piece of meat to silicon.

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