GNU Octave  4.0.0 A high-level interpreted language, primarily intended for numerical computations, mostly compatible with Matlab
ddot3.f
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1 c Copyright (C) 2009-2015 VZLU Prague, a.s., Czech Republic
2 c
3 c Author: Jaroslav Hajek <highegg@gmail.com>
4 c
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15 c GNU General Public License for more details.
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20 c
21  subroutine ddot3(m,n,k,a,b,c)
22 c purpose: a 3-dimensional dot product.
23 c c = sum (a .* b, 2), where a and b are 3d arrays.
24 c arguments:
25 c m,n,k (in) the dimensions of a and b
26 c a,b (in) double prec. input arrays of size (m,k,n)
27 c c (out) double prec. output array, size (m,n)
28  integer m,n,k,i,j,l
29  double precision a(m,k,n),b(m,k,n)
30  double precision c(m,n)
31
32  double precision ddot
33  external ddot
34
35
36 c quick return if possible.
37  if (m <= 0 .or. n <= 0) return
38
39  if (m == 1) then
40 c the column-major case.
41  do j = 1,n
42  c(1,j) = ddot(k,a(1,1,j),1,b(1,1,j),1)
43  end do
44  else
45 c We prefer performance here, because that's what we generally
46 c do by default in reduction functions. Besides, the accuracy
47 c of xDOT is questionable. Hence, do a cache-aligned nested loop.
48  do j = 1,n
49  do i = 1,m
50  c(i,j) = 0d0
51  end do
52  do l = 1,k
53  do i = 1,m
54  c(i,j) = c(i,j) + a(i,l,j)*b(i,l,j)
55  end do
56  end do
57  end do
58  end if
59
60  end subroutine
subroutine ddot3(m, n, k, a, b, c)
Definition: ddot3.f:21