stdlib_zhemm Subroutine

     pure subroutine stdlib_zhemm(side,uplo,m,n,alpha,a,lda,b,ldb,beta,c,ldc)
     !! ZHEMM performs one of the matrix-matrix operations
     !! C := alpha*A*B + beta*C,
     !! or
     !! C := alpha*B*A + beta*C,
     !! where alpha and beta are scalars, A is an hermitian matrix and  B and
     !! C are m by n matrices.
        ! -- reference blas level3 routine --
        ! -- reference blas is a software package provided by univ. of tennessee,    --
        ! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
           ! Scalar Arguments 
           complex(dp), intent(in) :: alpha, beta
           integer(ilp), intent(in) :: lda, ldb, ldc, m, n
           character, intent(in) :: side, uplo
           ! Array Arguments 
           complex(dp), intent(in) :: a(lda,*), b(ldb,*)
           complex(dp), intent(inout) :: c(ldc,*)
        ! =====================================================================
           ! Intrinsic Functions 
           intrinsic :: real,conjg,max
           ! Local Scalars 
           complex(dp) :: temp1, temp2
           integer(ilp) :: i, info, j, k, nrowa
           logical(lk) :: upper
           
           
           ! set nrowa as the number of rows of a.
           if (stdlib_lsame(side,'L')) then
               nrowa = m
           else
               nrowa = n
           end if
           upper = stdlib_lsame(uplo,'U')
           ! test the input parameters.
           info = 0
           if ((.not.stdlib_lsame(side,'L')) .and. (.not.stdlib_lsame(side,'R'))) then
               info = 1
           else if ((.not.upper) .and. (.not.stdlib_lsame(uplo,'L'))) then
               info = 2
           else if (m<0) then
               info = 3
           else if (n<0) then
               info = 4
           else if (lda<max(1,nrowa)) then
               info = 7
           else if (ldb<max(1,m)) then
               info = 9
           else if (ldc<max(1,m)) then
               info = 12
           end if
           if (info/=0) then
               call stdlib_xerbla('ZHEMM ',info)
               return
           end if
           ! quick return if possible.
           if ((m==0) .or. (n==0) .or.((alpha==czero).and. (beta==cone))) return
           ! and when  alpha.eq.czero.
           if (alpha==czero) then
               if (beta==czero) then
                   do j = 1,n
                       do i = 1,m
                           c(i,j) = czero
                       end do
                   end do
               else
                   do j = 1,n
                       do i = 1,m
                           c(i,j) = beta*c(i,j)
                       end do
                   end do
               end if
               return
           end if
           ! start the operations.
           if (stdlib_lsame(side,'L')) then
              ! form  c := alpha*a*b + beta*c.
               if (upper) then
                   do j = 1,n
                       do i = 1,m
                           temp1 = alpha*b(i,j)
                           temp2 = czero
                           do k = 1,i - 1
                               c(k,j) = c(k,j) + temp1*a(k,i)
                               temp2 = temp2 + b(k,j)*conjg(a(k,i))
                           end do
                           if (beta==czero) then
                               c(i,j) = temp1*real(a(i,i),KIND=dp) + alpha*temp2
                           else
                               c(i,j) = beta*c(i,j) + temp1*real(a(i,i),KIND=dp) +&
                                         alpha*temp2
                           end if
                       end do
                   end do
               else
                   do j = 1,n
                       do i = m,1,-1
                           temp1 = alpha*b(i,j)
                           temp2 = czero
                           do k = i + 1,m
                               c(k,j) = c(k,j) + temp1*a(k,i)
                               temp2 = temp2 + b(k,j)*conjg(a(k,i))
                           end do
                           if (beta==czero) then
                               c(i,j) = temp1*real(a(i,i),KIND=dp) + alpha*temp2
                           else
                               c(i,j) = beta*c(i,j) + temp1*real(a(i,i),KIND=dp) +&
                                         alpha*temp2
                           end if
                       end do
                   end do
               end if
           else
              ! form  c := alpha*b*a + beta*c.
               loop_170: do j = 1,n
                   temp1 = alpha*real(a(j,j),KIND=dp)
                   if (beta==czero) then
                       do i = 1,m
                           c(i,j) = temp1*b(i,j)
                       end do
                   else
                       do i = 1,m
                           c(i,j) = beta*c(i,j) + temp1*b(i,j)
                       end do
                   end if
                   do k = 1,j - 1
                       if (upper) then
                           temp1 = alpha*a(k,j)
                       else
                           temp1 = alpha*conjg(a(j,k))
                       end if
                       do i = 1,m
                           c(i,j) = c(i,j) + temp1*b(i,k)
                       end do
                   end do
                   do k = j + 1,n
                       if (upper) then
                           temp1 = alpha*conjg(a(j,k))
                       else
                           temp1 = alpha*a(k,j)
                       end if
                       do i = 1,m
                           c(i,j) = c(i,j) + temp1*b(i,k)
                       end do
                   end do
               end do loop_170
           end if
           return
     end subroutine stdlib_zhemm