root / synthbench / euroben-dm / mod2g / .svn / text-base / synthr.f.svn-base @ 0:839f52ef7657
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Subroutine synthr( a, w, n, m ) |
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! --------------------------------------------------------------------- |
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! --- 'synthr' does a Haar wavelet synthesis. Iput array is 'a'; |
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! output array is 'w'. Length is n and m = Log2(n). |
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! The code looks more complicated than is really is |
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! because of the hand-unrolling by a factor of 4 |
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! --------------------------------------------------------------------- |
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Use numerics |
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Integer :: n, m |
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Real(l_) :: a(n), w(n) |
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|
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Integer :: i, j, j2, k, n1 |
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Logical :: odd |
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! --------------------------------------------------------------------- |
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n1 = 1 |
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odd = .TRUE. |
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w(1) = a(1) |
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Do i = 1, m |
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If ( odd ) Then |
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If ( n1 >= 4 ) Then |
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Do j = 1, n1, 4 |
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w(j*2-1) = a(j) + a(j+n1) |
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w(j*2) = a(j) - a(j+n1) |
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w(j*2+1) = a(j+1) + a(j+n1+1) |
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w(j*2+2) = a(j+1) - a(j+n1+1) |
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w(j*2+3) = a(j+2) + a(j+n1+2) |
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w(j*2+4) = a(j+2) - a(j+n1+2) |
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w(j*2+5) = a(j+3) + a(j+n1+3) |
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w(j*2+6) = a(j+3) - a(j+n1+3) |
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End Do |
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Else If ( n1 >= 2 ) Then |
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Do j = 1, n1, 2 |
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w(j*2-1) = a(j) + a(j+n1) |
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w(j*2) = a(j) - a(j+n1) |
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w(j*2+1) = a(j+1) + a(j+n1+1) |
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w(j*2+2) = a(j+1) - a(j+n1+1) |
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End Do |
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Else |
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Do j = 1, n1 |
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w(j*2-1) = a(j) + a(j+n1) |
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w(j*2) = a(j) - a(j+n1) |
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End Do |
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End If |
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Else |
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If ( n1 >= 4 ) Then |
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Do j = 1, n1, 4 |
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a(j*2-1) = w(j) + a(j+n1) |
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a(j*2) = w(j) - a(j+n1) |
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a(j*2+1) = w(j+1) + a(j+n1+1) |
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a(j*2+2) = w(j+1) - a(j+n1+1) |
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a(j*2+3) = w(j+2) + a(j+n1+2) |
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a(j*2+4) = w(j+2) - a(j+n1+2) |
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a(j*2+5) = w(j+3) + a(j+n1+3) |
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a(j*2+6) = w(j+3) - a(j+n1+3) |
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End Do |
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Else If ( n1 >= 2 ) Then |
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Do j = 1, n1, 2 |
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a(j*2-1) = w(j) + a(j+n1) |
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a(j*2) = w(j) - a(j+n1) |
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a(j*2+1) = w(j+1) + a(j+n1+1) |
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a(j*2+2) = w(j+1) - a(j+n1+1) |
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End Do |
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Else |
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Do j = 1, n1 |
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a(j*2-1) = w(j) + a(j+n1) |
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a(j*2) = w(j) - a(j+n1) |
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End Do |
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End If |
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End If |
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n1 = n1 + n1 |
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odd = .NOT. odd |
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End Do |
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If ( m == 2*(m/2) ) w = a |
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! --------------------------------------------------------------------- |
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End Subroutine synthr |