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Linear system

As explained in Math and Architectures of Deep Learning

A set of linear equations considered together, typically represented in matrix form and solved for unknown variables.

A linear system is a set of simultaneous linear equations treated together and often written in matrix form. The compact matrix form scales better than listing equations one by one, especially when many unknowns are involved. section 2.12

The basic goal is to find unknown values that make the matrix equation true. In the simple square, invertible case, the solution parallels the one-variable rule x = a−1b. section 2.12

Key behaviors of linear systems in this treatment:

  • Square, invertible systems have an exact solution through matrix inverse. section 2.12
  • Zero determinants make the system singular and unsolvable exactly. section 2.12.1
  • Near-zero determinants make the system numerically unstable. section 2.12.1
  • Non-square systems are handled with the Moore-Penrose pseudo-inverse or SVD-based methods. section 2.12.4 section 4.5.4

Toy training equations

A small machine learning example turns training data into equations such as 0.11w0 + 0.09w1 + b = −0.8 and similar rows for other samples. The same setup is also shown as a larger overdetermined system with many training examples. section 2.12 section 2.12.4

a11x1 + a12x2 + a13x3 + … + a1nxn = b1
a21x1 + a22x2 + a23x3 + … + a2nxn = b2
                           ⁞
an1x1 + an2x2 + an3x3 + … + annxn = bn

Shows the general n-equation, n-unknowns layout in explicit row form. section 2.12

How Math and Architectures of Deep Learning covers it

How deep it goes
Defines matrix form, exact and approximate solving, singularity, and SVD-based alternatives.
Examples
Uses toy training data, repeated equations, and overdetermined systems as concrete cases.
What it assumes
Assumes matrix multiplication basics and introduces inverse and determinant ideas from first principles.
What you can do after
Apply pseudo-inverse or SVD to solve exact, approximate, or nonsquare systems.
How it connects
Links matrix inverse, determinant, singular matrix, pseudo-inverse, SVD, and column space.

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This explainer was generated by Manning's knowledge graph from the text of Math and Architectures of Deep Learning. The section links point to the parts of the book it draws on.