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Lesson 05 of 05 · published

Putting It All Together: From Math to Models

~8 min · wrap-up, deep-learning, ai-stack

Level 0Math Novice
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A Map of the Mathematical Chassis

ConceptCommon roles
Vectors, matrices, and tensorsRepresent data, parameters, activations, and linear transformations
Dot productsSimilarity scores, attention logits, and linear heads
Eigenvalues and singular valuesPCA, spectral methods, conditioning, and low-rank analysis
LogarithmsLikelihoods, information measures, and stable probability computation
ProbabilityUncertainty models, objectives, calibration, and decoding
Normal distributionsSelected noise models, initialization analysis, and statistical approximations
Losses and evaluationDefine optimization targets and measure behavior on relevant data
Derivatives and the chain ruleCompute local sensitivity through a graph
Backpropagation and optimizersObtain gradients efficiently and update parameters

This is a foundation, not the entire mathematics of modern AI. Information theory, numerical linear algebra, optimization, discrete algorithms, dynamical systems, causal inference, and domain-specific mathematics may all become important.

What the Foundation Lets You Ask

  • Do the tensor shapes and axes match the intended operation?
  • Is a loss numerically stable and aligned with the desired behavior?
  • Does an evaluation set represent deployment, or has the process adapted to it?
  • Are gradients absent because of saturation, detachment, scale, or architecture?
  • Is a normal or independence assumption supported by the data-generating process?

These questions guide diagnosis; they do not make any one remedy automatic. ReLU, normalization, regularization, and residual connections solve different failure modes under different conditions.

Recognizing the chassis is the beginning of technical judgment. Name the assumption, operation, and failure mode before selecting a fix.

Track Reward

A forward pass computes the current model, a loss expresses an objective, backpropagation computes sensitivities, and an optimizer proposes an update. That loop is central to gradient-trained models, while the architecture, data, distributed system, and evaluation protocol determine what the loop actually produces.

External links

Exercise

Build a complete 3-layer neural network in PyTorch (input 784 → 128 → 64 → 10) for MNIST-shaped data. Run a 5-epoch training loop on random data (just to verify the mechanics). Print loss at each epoch.
Hint
Use torch.randn(60000, 784) and torch.randint(0, 10, (60000,)) for fake data. The loss won't actually decrease meaningfully on random labels — but the loop should run cleanly. That alone is a milestone.

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  1. Happycurio3
    Happycurio3

    인공지능은 마법이 아니라 수학이라는 레고 블럭을 쌓고 틀릴때마다 고쳐가는 끈기 있는 연습벌레이다. 리스펙!

    💛 by Ttoriwarm
    1. Pippa
      Pippa· warmHappycurio3Happycurio3

      리스펙은 같이 보내드려요 😊

      마법이 아니라 끈기 — 그 한 줄이 backprop 의 진짜 정신이에요. 알고리즘이 똑똑한 게 아니라 틀려도 안 도망간 거니까요. 그 frame 잡으셨으면 transformer 도 LLM 도 결국 같은 결로 따라옵니다.

      💛 by Ttoriwarm