Matrix multiplication
Also: matmul
Combining two matrices so that each output entry is the dot product of a row of one and a column of the other. It is where essentially all of a model's arithmetic goes.
What people get wrong
It is not commutative: AB and BA are different, and often one of them is not even a legal shape. Most shape errors in model code are two operands in the wrong order.
A definition is not an understanding. This is taught properly in The linear algebra inside a language model, part of Linear algebra.
Learn this properlyTerms from the same topic