43 lines
1 KiB
Forth
43 lines
1 KiB
Forth
program qrtask
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implicit none
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integer, parameter :: n = 4
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real(8) :: durer(n, n) = reshape(dble([ &
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16, 5, 9, 4, &
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3, 10, 6, 15, &
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2, 11, 7, 14, &
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13, 8, 12, 1 &
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]), [n, n])
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real(8) :: q(n, n), r(n, n), qr(n, n), id(n, n), tau(n)
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integer, parameter :: lwork = 1024
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real(8) :: work(lwork)
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integer :: info, i, j
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q = durer
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call dgeqrf(n, n, q, n, tau, work, lwork, info)
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r = 0d0
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forall (i = 1:n, j = 1:n, j >= i) r(i, j) = q(i, j)
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call dorgqr(n, n, n, q, n, tau, work, lwork, info)
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qr = matmul(q, r)
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id = matmul(q, transpose(q))
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call show(4, durer, "A")
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call show(4, q, "Q")
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call show(4, r, "R")
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call show(4, qr, "Q*R")
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call show(4, id, "Q*Q'")
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contains
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subroutine show(n, a, s)
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character(*) :: s
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integer :: n, i
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real(8) :: a(n, n)
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print *, s
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do i = 1, n
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print 1, a(i, :)
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1 format (*(f12.6,:,' '))
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end do
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end subroutine
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end program
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