hermitianEigen fortran zheevd bench

hermitianEigen-small.f90

! --------------------------------------------------------
! compile command line:
! ifort -O2 -i8 -mcmodel=medium -qmkl=parallel ./hermitianEigen-small.f90 -o ./hermitianEigen-small  ${MKLROOT}/lib/intel64/libmkl_lapack95_ilp64.a -L${MKLROOT}/lib/intel64 -lpthread -lm -ldl
! --------------------------------------------------------

program hermitianEigen

    use, intrinsic :: iso_fortran_env
    use lapack95, only: heevd

    ! default integer precision
    integer, parameter :: ip = INT64
    ! default real precision
    integer, parameter :: fp = REAL64
    ! square matrix dimension
    integer, parameter :: n = 4096
    ! real matrices
    real(fp), dimension(:), allocatable   :: w
    real(fp), dimension(:,:), allocatable :: a
    ! complex matrix
    complex(fp), dimension(:,:), allocatable :: c, tmp
    integer(ip) :: start, end, rate
    intrinsic :: random_seed, random_number

    ! record start time
    call system_clock (count_rate=rate)
    call system_clock (count=start)

    ! allocate memory
    allocate(w(n), a(n,n), c(n,n), tmp(n,n))

    ! generate our random (real and imaginary) matrix elements
    print*, '01. Generating random numbers for hermitian matrix...'
    print*, '02. Building our positive definite hermitian matrix...'
    call random_number(a)
    tmp%re = a
    call random_number(a)
    tmp%im = a

    ! free some memory
    deallocate(a)

    ! ensure its hermitian
    !c = c * conjg(transpose(c)) ! FATAL: produces seg fault with ifort, requires tmp to avoid!
    c = tmp * conjg(transpose(tmp))

    deallocate(tmp)

    ! positive-definite
    do concurrent (i=1:n)
        c(i,i) = c(i,i) + n
    end do

    call heevd(c, w, 'V')

    call system_clock (count=end)
    write(*,"(a,f8.3,a)") "ZHEEVD took: ", real(end - start)/real(rate), " seconds"

end program hermitianEigen