Random Forest from Scratch
Follow the data, decisions, feedback, and validation boundaries before writing the full system.
How to read this diagram
Read left to right for the forward path: raw information becomes a representation, passes through the project’s main computational ideas, and produces an output that can be measured. Then follow the feedback path back toward the trainable or decision-making components.
Gini impurity
Gini impurity is the probability of misclassifying a label drawn from a node when the label is sampled from that node’s class distribution. A pure node has impurity zero. A split is useful only when the sample-weighted impurity of its children is lower than the parent’s impurity.
Boundary check: document its accepted input, output shape, mutable state, failure modes, and the metric that proves this stage is correct before connecting it downstream.
Bagging
Bagging trains estimators on bootstrap samples drawn with replacement. Each learner sees a slightly different empirical distribution. Averaging their predictions keeps shared signal while cancelling part of their uncorrelated variance.
Boundary check: document its accepted input, output shape, mutable state, failure modes, and the metric that proves this stage is correct before connecting it downstream.
Feature sampling
Autoregressive modeling factorizes a sequence into next-token conditional probabilities. A causal mask blocks future information; temperature, top-k, and nucleus sampling reshape the distribution at inference without retraining.
Boundary check: document its accepted input, output shape, mutable state, failure modes, and the metric that proves this stage is correct before connecting it downstream.
Architecture review checklist
- Every arrow has a documented shape, dtype, unit, or schema.
- Training and evaluation paths cannot leak information into each other.
- Randomness is seeded and captured in experiment metadata.
- Expensive stages expose timing, memory, throughput, and error metrics.
- Each feedback loop has a stop condition and a rollback strategy.
- Small reference implementations exist for numerical comparisons.