GNU Octave  3.8.0
A high-level interpreted language, primarily intended for numerical computations, mostly compatible with Matlab
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dmatm3.f
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1 c Copyright (C) 2009-2013 VZLU Prague, a.s., Czech Republic
2 c
3 c Author: Jaroslav Hajek <highegg@gmail.com>
4 c
5 c This file is part of Octave.
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20 c
21  subroutine dmatm3(m,n,k,np,a,b,c)
22 c purpose: a 3-dimensional matrix product.
23 c given a (m,k,np) array a and (k,n,np) array b,
24 c calculates a (m,n,np) array c such that
25 c for i = 1:np
26 c c(:,:,i) = a(:,:,i) * b(:,:,i)
27 c
28 c arguments:
29 c m,n,k (in) the dimensions
30 c np (in) number of multiplications
31 c a (in) a double prec. input array, size (m,k,np)
32 c b (in) a double prec. input array, size (k,n,np)
33 c c (out) a double prec. output array, size (m,n,np)
34  integer m,n,k,np
35  double precision a(m*k,np),b(k*n,np)
36  double precision c(m*n,np)
37 
38  double precision ddot,one,zero
39  parameter(one = 1d0, zero = 0d0)
40  external ddot,dgemv,dgemm
41  integer i
42 
43 c quick return if possible.
44  if (np <= 0) return
45 
46  if (m == 1) then
47  if (n == 1) then
48  do i = 1,np
49  c(1,i) = ddot(k,a(1,i),1,b(1,i),1)
50  end do
51  else
52  do i = 1,np
53  call dgemv("T",k,n,one,b(1,i),k,a(1,i),1,zero,c(1,i),1)
54  end do
55  end if
56  else
57  if (n == 1) then
58  do i = 1,np
59  call dgemv("N",m,k,one,a(1,i),m,b(1,i),1,zero,c(1,i),1)
60  end do
61  else
62  do i = 1,np
63  call dgemm("N","N",m,n,k,
64  + one,a(1,i),m,b(1,i),k,zero,c(1,i),m)
65  end do
66  end if
67  end if
68 
69  end subroutine