_index.org

Numerical Linear Algebra

Last edited: February 2, 2026

FLOP

A FLOP is a “floating-point operations”. One addition, subtraction, multiplication, or division of two floating-point numbers.

Basic Linear Algebra Subroutines

BLAS Level 1

Vector-Vector operations

  • inner product \(x^{T}y\) which is \(2n-1\) flops
  • sum \(x+y\) and scale \(\alpha x\) which is \(n\) flops

BLAS Level 2

Matrix-vector product

\(y = Ax\) with \(A \in \mathbb{R}^{m \times n}\)

  • standard multiply \(m\qty(2n - 1)\)
  • \(2N\) if \(A\) is sparse with \(N\) non-zero elements
  • \(2p\qty(n+m)\) if \(A\) is given as \(A = UV^{T}\), where \(U \in \mathbb{R}^{m \times p}\) and \(V \in \mathbb{R}^{n \times p}\), which is called a “banded” matrix (sparse everywhere except for a strip nexht to diagonal)

BLAS Level 3

Matrix-matrix operations

SU-EE364A FEb192026

Last edited: February 2, 2026

Key Sequence

Notation

New Concepts

Important Results / Claims

Questions

Interesting Factoids

SU-EE364A FEB242026

Last edited: February 2, 2026

Key Sequence

Notation

New Concepts

Important Results / Claims

Questions

Interesting Factoids

SU-SOC175 FEB232026

Last edited: February 2, 2026

Implications: rapid population aging. 1-child policy means that cost of pensions, health care, and social services will thus rise.

  • 1 in 6 now above 60
  • 1 in 4 above 2030
  • 1 in 3 by 2050

“get old before getting rich”

demography

1980-2010

  • low dependency ratios
  • high household savings rate
  • large lavor supply
  • “age of abundance”

decline

  • rapidly aging population
  • rapidly rising dependency ratios
  • ageing population / rising health / retirement costs
  • shrikning labor force, rising wages
  • declining of deposits in bank system
  • less capital

resulting dynamics

  • labor force shrinking by 2 million workers per year
  • manufacturing wages rising faster
  • labor cost advantage almost gone

wages keep going up

Knee Socks

Last edited: February 2, 2026

You got the lights on in the afternoon

And the nights are drawn out long

And you’re kissin’ to cut through the gloom

With a cough drop coloured tongue

And you were sittin’ in the corner with the coats all piled high

And I thought you might be mine

In a small world, on an exceptionally rainy Tuesday night

In the right place and time

When the zeros line up on the 24 hour clock