product of an nxn matrix with nx1 vector

[humaira fazal]

Hi,

 I'm trying to multiply an nxn matrix with nx1 vector.

var A{i in N,j in N}

var r{j in N}

var A{j in N}=B[i,j]*r[j];

 

 Also I have to reshape  an n^2x1 vector into nxn matrix.

Can anyone please tell me the syntax of it.

thanks

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[Robert Fourer]

I'm not sure what is intended here, but the following is one example of matrix-vector multiplication:

 

   param N integer > 0;

   param A {1..N,1..N};

   var r {1..N};

 

   var v {i in 1..N} = sum {j in 1..N} A[i,j] * r[j];

 

The reshape will involve an assignment like

 

   let {i in 1..N, j in 1..N} Mat[i,j] := vect[N*(i-1)+j];

 

but I will leave the details to the reader.

 

Bob Fourer

4...@ampl.com=

 

 

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From: am...@googlegroups.com [mailto:am...@googlegroups.com] On Behalf Of humaira fazal
Sent: Monday, May 12, 2008 4:35 PM
To: am...@googlegroups.com
Subject: [AMPL 1775] product of an nxn matrix with nx1 vector