The Slime Algorithm: Biological Computing

When we think of “calculating,” we think of silicon chips and binary code. But Physarum polycephalum calculates with liquid pressure and slime.

In the world of computer science, the blob is a celebrity. It is a living manifestation of some of the most famous algorithms in history.

1. Mimicking the Dijkstra Algorithm

The Dijkstra Algorithm is how your GPS finds the fastest route from your house to the airport. It scouts every possible path and chooses the one with the lowest “cost” (distance or time).

How the Blob does it:

• The Flood: The blob scouts the entire area, filling every available “road” in a maze.
• The Connection: Once it finds food at two points, it starts a positive feedback loop.
• The Physics: Protoplasm flows faster through paths that feel “right.” This increased flow thickens the veins (increasing conductivity), while paths that don’t lead to food eventually starve and shrink.

2. Solving the Steiner Tree Problem

The Steiner Tree Problem asks: “How do you connect a set of points using the shortest possible total length of pipe?”

The Tokyo Subway experiment proved that the blob is a master of this. It doesn’t just connect point A to B; it creates a network. It minimizes the total cost (the amount of slime used) while maximizing resilience (creating loops so that if one path is blocked, the food still flows).

3. The Logic of “Fluid Logic Gates”

Scientists have successfully used slime molds to create Logic Gates (the building blocks of computers like AND, OR, and NOT).

• The Setup: Researchers use chemicals (like Quinine) or light to guide the blob through specific channels.
• The Logic: If the blob is at Input A and Input B, it will only move to Output C if the conditions are met.
• The Result: A biological circuit board that can process simple “True/False” statements through its own physical growth.

4. The Future: Physarum-Inspired Computing

Computer engineers are no longer just letting the blob solve mazes; they are copying its code.

Instead of writing traditional software, they are creating “Slime Simulations” to:

• Design Fiber Optic Networks: Finding the most resilient paths between cities.
• Analyze Social Networks: Seeing how information “flows” through human groups.
• Medical Modeling: Using the blob’s veins to predict how cancer tumors recruit blood vessels (angiogenesis).

Scientific Fact: This biological paradigm is called “Unconventional Computing.” It suggests that we don’t always need a central processor (a brain or a CPU) to solve a massive problem—you just need a decentralized system that follows a few simple rules of flow.

Curious about how it physically does this? See the Anatomy of a Syncytium.