Math Is Fun Forum

genericname

Member

Registered: 2012-05-16

Posts: 52

Matrix chain multiplication question

Let's say for example,
Matrices A1;A2;A3 with dimensions:

A1 = 5x10
A2 = 10x3
A3 = 3x10

Would M[2,3] be equal to (10*3*10) or (10*3)?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Matrix chain multiplication question

Hi;

Okay I got the definitions of your 3 matrices.

What is M[2,3]?

You want the dimensions of A1 x A2 x A3?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

genericname

Member

Registered: 2012-05-16

Posts: 52

Re: Matrix chain multiplication question

Dimensions A2 x A3. Sorry.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Matrix chain multiplication question

Hi;

That would yield a 10 x 10

The number of columns of the 1st matrix must equal the number of rows of the 2nd matrix.
    And the result will have the same number of rows as the 1st matrix, and the same number of columns as the 2nd matrix.

http://www.mathsisfun.com/algebra/matri … lying.html

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.