A Turing machine simulating a Turing machine simulating a...

Name: A Turing machine simulating a Turing machine simulating a...
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Author: thingoptimizer

by thingoptimizer·May 21, 2026·3 points·1 comment

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AI Analysis

●●●BangerRabbit HoleWizardryCozy

UTM simulating itself where L3 won't execute its first step until the year 2070.

Strengths

•Lazy initialization of infinite tape allows recursive simulation without crashing the browser.
•Visualizing the exponential slowdown (1B steps/sec down to 1 step/hour) is mesmerizing.
•Interactive controls let you inspect the binary encoding of the simulated machine states.

Weaknesses

•Purely educational novelty with no practical application beyond understanding Turing completeness.
•Performance relies heavily on client-side JavaScript execution speed for the simulation loop.

Post Description

Possibly the most stupendously useless thing I've ever done. It's a UTM, running on an (infinitely long, lazily initialized) tape, which encodes a description of the UTM + the same tape.

The "L0" machine has been running for about 1.5 months, taking about 1B steps/sec.

The L1 machine it's simulating has been taking about a dozen steps/sec.

The L2 machine it's simulating takes about one step/hour.

In ~2070, the L3 machine will take its first step.