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Matrix/vector multiplication

 
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myseyi123



Joined: 05 Mar 2015
Posts: 1
PostPosted: Fri Mar 06, 2015 12:11 pm    Post subject: Matrix/vector multiplication Reply with quote
I am new to fortran 95. I need help on how to multiply matrix and vectors. I have consulted books and online tutorial but to no avail.
Also, is silverfrost FTN95 code different from that of other publishers?
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JohnCampbell



Joined: 16 Feb 2006
Posts: 2554
Location: Sydney
PostPosted: Sat Mar 07, 2015 11:28 pm    Post subject: Reply with quote
There are intrinsic functions to help with this.
Dot_Product will multiply 2 vectors.
MATMUL will multiply 2 matrices of rank 2.

You need to understand how to declare the arrays and then use intrinsic functions. As you say you are new to Fortran 95, I am not sure to what detail you require further help. I suggest you google Fortran tutorials and see if you can follow the examples they have.

John
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davidb



Joined: 17 Jul 2009
Posts: 560
Location: UK
PostPosted: Sun Mar 08, 2015 4:34 pm    Post subject: Reply with quote
It is difficult to know what is being asked here. Help with the maths or help with code?

MATMUL can be used in 3 ways (using numeric data).

Code:

C = MATMUL(A,B)


(1) If A has shape (M,K) and B has shape (K,N), C will have shape (M,N)
(2) If A has shape (K) and B has shape (K,M), C will have shape (M)
(3) If A has shape (N, K) and B has shape (K), C will have shape (N)

(1) C(i,j) has the value SUM(A(i,:)*B(:,j)
(2) C(j) has the value SUM(A(:)*B(:,j))
(3) C(i) has the value SUM(A(i,:)*B(:))
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