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David H. Ackley
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Proceedings Papers
. isal2020, ALIFE 2020: The 2020 Conference on Artificial Life13-15, (July 13–18, 2020) doi: 10.1162/isal_a_00337
Abstract
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Computer architectures that presume global hardware determinism are ultimately unscalable, but they are relatively easy to program because each operation is strictly sequenced and has an assured effect. Architectures that forgo global determinism can be indefinitely scalable , but they demand a shift in programming concepts, towards software mechanisms that can perform useful work given only limited, local synchronization and merely best-effort determinism. This paper introduces a parallel computing framework called SPOT— Stage Priority Operation Teams —designed for ulam programmers coding for the 2D grid of the Movable Feast Machine. Spatial threads , a simple but flexible 1D distributed programming paradigm, are introduced as a first use-case for SPOTs, with sample tasks ranging from moving objects to search, quorum sensing, and data reductions. SPOT and spatial threads also make intriguingly literal connections between crass physical concepts—such as space, time, and motion—and computational concepts such as program and data, and suggest a humble but fundamentally sensible meaning for the term ‘object’.
Proceedings Papers
. isal2019, ALIFE 2019: The 2019 Conference on Artificial Life111-118, (July 29–August 2, 2019) doi: 10.1162/isal_a_00149
Abstract
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A computer produces outputs from inputs, and to do so reliably, its internal noise and variability must be managed effectively. Traditional computer architecture requires hardware determinism , but such perfect repeatability is increasingly incompatible with large-scale and real-world systems. Natural living systems, without the luxury of deterministic hardware, manage variability across the computational stack—and using such principles, soft artificial life offers a route to much larger and safer manufactured computers. This paper describes the engineering development of C214 , a next-generation self-constructing digital protocell. C214 struggles to survive in a challenging environment that, while not literally malicious, goes well beyond merely non-deterministic to deliberately destructive. Improved self-repair mechanisms, as well as active defenses in depth, give the new cell’s membrane a median survival time more than ten times greater than that of the earlier C211 . A new grid-based cytoplasm is also presented, standing to offer a more stable environment for future layers of the ‘living computation stack’
Proceedings Papers
. alife2018, ALIFE 2018: The 2018 Conference on Artificial Life83-90, (July 23–27, 2018) doi: 10.1162/isal_a_00021
Abstract
PDF
In spatial computational models such as cellular automata (CA), designing mobile objects larger than the CA neighborhood is challenging when the object properties and dynamics are incompletely specified in advance. This paper introduces C211 , a two-dimensional digital ‘protocell’ with life-like and potentially useful features, designed for the best-effort asynchronous CA called the Movable Feast Machine (MFM). The protocell consists of an amorphous variable-density ‘cytoplasm’ that uses gossiping to coordinate operations such as cell movements, surrounded by an asymmetric ‘bilayer membrane’ providing some environmental isolation while adapting to cytoplasmic dynamics. C211 was engineered in a new ‘little language’ called SPLAT, which adds discrete 2D spatial pattern transforms to the ulam programming language. SPLAT is expressive enough that minimal code was required, for example, to enable membrane topology changes such as cell splitting and fusion. C211 ’s cytoplasm maintains internal state but leaves dozens of bits unused per atom, while its membrane is purely stigmergic and stateless—so vast tracts of pristine CA state space remain available for future cellular dynamics, whether engineered, evolved, or both.
Proceedings Papers
. ecal2015, ECAL 2015: the 13th European Conference on Artificial Life554-561, (July 20–24, 2015) doi: 10.1162/978-0-262-33027-5-ch097