The Modern Mathematics of Deep Learning

A ReLU tent function

Penguin learning project

The project uses 342 complete Palmer penguin records: 240 training-pool and 102 held-out rows. The selected training rows determine feature scaling and model parameters. Source CSV

This project trains weights with softmax, unlike the homepage lab, which uses nearest species averages. Same penguin measurements; different classification methods. Predictions can differ.

Functions and derivatives · Describe maps and how their outputs change.

Project vectors have two features; the training matrix has n rows and two columns. Mathematical tools may operate on these values when their assumptions apply.

Consider this concept alongside the project; its source assumptions may differ. These observations do not prove a theorem.

Input: 12 × 2; Held-out evaluation: 102 · #58 · 40.6 mm, 193 mm. Known answer: Adélie; Prediction: Adélie · [≈0.7383, ≈0.2444, ≈0.01737].

Used in these source sections: 3.2 Simple pieces, many layers

On the left half the value is 2x. On the right half it is 2(1−x). Both give 1 at x = 1/2.

The source composes this function when studying deep ReLU approximation.

Source formula example

\begin{split}h\colon[0,1]&\to[0,1],\\ x&\mapsto 2{\varrho_{R}}(x)-4{\varrho_{R}}(x-\tfrac{1}{2})=\begin{cases}2x,&\text{if }0\leq x<\tfrac{1}{2},\\ 2(1-x),&\text{if }\tfrac{1}{2}\leq x\leq 1,\end{cases}\end{split}

exact · The result is exact for these finite toy inputs, apart from ordinary computer rounding.

Symbols

$x$: A real number in the closed unit interval.

Source formula example

This source example uses its own inputs and assumptions. Editing it does not change the project.

Edit a value or the code, then run the example. This is a finite demonstration, not a proof of the paper’s theorem.

x

This example’s data flow

You choose

input.x = 0.75

Calculated here

Result expression: { value: 2 * relu(input.x) - 4 * relu(input.x - 0.5) }

Returns

Example result

value: 0.5

JavaScript

Read numbers from input and return the result. JavaScript basics.

Result

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Technical statement

Change the input and run the same code again. The displayed result uses the values shown above.

Source: Source expression