z2mm.f90

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! Copyright (C) 2007 J. K. Dewhurst, S. Sharma and C. Ambrosch-Draxl.
! This file is distributed under the terms of the GNU Lesser General Public
! License. See the file COPYING for license details.
 
!BOP
! !ROUTINE: z2mm
! !INTERFACE:
pure subroutine z2mm(a,b,c)
! !INPUT/OUTPUT PARAMETERS:
!   a : input matrix 1 (in,complex(2,2))
!   b : input matrix 2 (in,complex(2,2))
!   c : output matrix (out,complex(2,2))
! !DESCRIPTION:
!   Multiplies two complex $2\times 2$ matrices. Note that the output matrix
!   cannot be one of the input matrices.
!
! !REVISION HISTORY:
!   Created October 2007 (JKD)
!EOP
!BOC
implicit none
! arguments
complex(8), intent(in) :: a(2,2),b(2,2)
complex(8), intent(out) :: c(2,2)
c(1,1)=a(1,1)*b(1,1)+a(1,2)*b(2,1)
c(2,1)=a(2,1)*b(1,1)+a(2,2)*b(2,1)
c(1,2)=a(1,1)*b(1,2)+a(1,2)*b(2,2)
c(2,2)=a(2,1)*b(1,2)+a(2,2)*b(2,2)
end subroutine
!EOC