29 lines
681 B
Fortran
29 lines
681 B
Fortran
C Eratosthenes Sieve from BYTE magazine
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program sieve
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logical flags( 8191 )
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integer*2 i, prime, k, count
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integer*2 iter
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write( *, 50 )
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50 format( ' 10 iterations' )
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do 92 iter = 1, 10
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count = 0
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do 10 i = 0, 8190
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10 flags( i ) = .true.
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do 91 i = 0, 8190
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if ( .not. flags( i ) ) go to 91
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prime = i + i + 3
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k = i + prime
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20 if ( k .gt. 8190 ) go to 90
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flags( k ) = .false.
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k = k + prime
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go to 20
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90 count = count + 1
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91 continue
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92 continue
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write( *, 200 ) count
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200 format( 1X, I6, ' primes' )
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stop
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100 format( 1X, I6 )
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end
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