root / synthbench / euroben-dm / mod2g / log2.f @ 0:839f52ef7657
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Integer Function log2( n ) |
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! --------------------------------------------------------------------- |
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Implicit None |
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Integer :: n |
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|
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Integer :: m, nl |
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! --------------------------------------------------------------------- |
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If ( n < 1 ) Then |
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Print *, '*** ERROR in function LOG2: Argument ', n, |
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& ' is not valid. (< 1).' |
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log2 = -1 |
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Return |
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End If |
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If ( n == 1 ) Then |
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log2 = 0 |
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Return |
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End If |
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nl = n |
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m = 0 |
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Do |
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If ( Mod( nl, 2 ) /= 0 .AND. ( nl /= 1 ) ) Then |
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Print *, '***ERROR in function LOG2: Argument ', n, |
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& ' is not a power of 2.' |
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log2 = -1 |
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Return |
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End If |
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If ( nl == 1 ) Exit |
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nl = nl/2 |
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m = m + 1 |
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End Do |
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log2 = m |
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! --------------------------------------------------------------------- |
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End Function log2 |