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Notation

This book uses consistent notation throughout. Below is a reference guide for the symbols and conventions used.

Sets and Number Systems

Real numbers
n n-dimensional real vectors
+, +n Non-negative reals / non-negative real vectors
Integers
+, +n Non-negative integers / non-negative integer vectors
Rational numbers
{0,1}n Binary vectors of dimension n

Vectors and Matrices

x,y,z Decision variable vectors (bold lowercase)
a,b,c Parameter vectors (bold lowercase)
0 Zero vector
A,B Matrices (capital italic)
xi i-th component of vector x
aij Element in row i, column j of matrix A
x Transpose of vector x
A Transpose of matrix A
cx Dot product (inner product) of c and x
x Norm of vector x

Optimization Problems

A standard linear program is written as:

max cx  s.t. Ax b x 0
max , min Maximize, minimize
s.t. Subject to (constraints follow)
, , = Constraint types
x Optimal solution
z Optimal objective value

Summation and Indexing

i=1nxi Sum of x1 + x2 + + xn
iIxi Sum over all indices in set I
i=1nxi Product x1 x2xn
i I For all i in set I
There exists

Functions and Operators

f(x) Function of x
f Gradient of f
2f Hessian matrix of f
argmin xf(x) Value of x that minimizes f
conv (S) Convex hull of set S
dom (f) Domain of function f

Complexity Classes

Polynomial time (P) Polynomial-time solvable
NP-complete NP-Complete problem
NP-hard NP-Hard problem

Common Abbreviations

LP Linear Programming
IP Integer Programming
ILP Integer Linear Programming
BIP Binary Integer Programming
MILP Mixed-Integer Linear Programming
NLP Nonlinear Programming
MINLP Mixed-Integer Nonlinear Programming

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