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Mixture of experts

As explained in Build Applications with Local AI Models on a Mac

A neural network architecture that routes inputs through selected expert subnetworks rather than activating every parameter for every input.

A mixture-of-experts (MoE) model keeps many specialized subnetworks, called experts, but uses only a few for each token. A router selects which experts activate; the rest stay idle. In a dense model, every parameter—the learned numerical values stored in the model—activates for every token. MoE reduces the computation needed to generate a token without making every expert work on it. section 12.5.1 section 12.2.2

The router and experts are not assigned fixed jobs in advance. They start with random weights and learn together during training: the router learns which experts to select, while the experts develop specializations. This creates two useful size measures: total parameters describe the model’s overall capacity, while active parameters indicate how much of it computes each token. section 12.5.1

An 80B model with 3B active

Qwen3-Coder-Next has about 80 billion parameters in total, but activates about 3 billion per token. That smaller active count helps explain its generation speed; it does not mean the whole model needs only 3B-sized storage. One Ollama build is approximately 52 GB to download, and running it needs additional memory for context and overhead. Check the build and available RAM before downloading. section 12.5.3 section 17.3.1

Table 12.5 Key specifications of Qwen3-Coder-Next

Specification

Value

Total parameters

80 billion

Active parameters

3 billion

Expert count

512 (10 active per token + 1 shared)

Context window

256,000 tokens

License

Open

Architecture

Ultra-sparse MoE

Compare Qwen3-Coder-Next’s total and active parameters, then see how many experts its ultra-sparse design uses per token. section 12.5.3

How Build Applications with Local AI Models on a Mac covers it

How deep it goes
Explains routing, expert activation, and joint training in plain language, without implementation details.
Examples
Uses GLM-5’s 744B-total/40B-active contrast and Qwen3-Coder-Next’s 80B-total/3B-active specifications.
What it assumes
Defines parameters as learned numerical values and tokens as model-sized pieces of text.
What you can do after
Evaluate/understand MoE model specifications by separating per-token computation from download size and RAM needs.
How it connects
Links MoE to dense models, token generation, quantization, and local hardware requirements.

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This explainer was generated by Manning's knowledge graph from the text of Build Applications with Local AI Models on a Mac. The section links point to the parts of the book it draws on.