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Improvement to prime-sieve model solution #29

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Improvement to prime-sieve model solution #29

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12 changes: 4 additions & 8 deletions solutions/section2.03-2/solution.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -23,30 +23,26 @@ program exercise2
implicit none

integer, parameter :: nmax = 120
integer, dimension(2:nmax) :: ia
logical, dimension(2:nmax) :: isprime

integer :: n, p

do n = 2, nmax
ia(n) = n
isprime(n) = .true.
end do

do p = 2, nmax
do n = 2*p, nmax
if (mod(n,p) == 0) isprime(n) = .false.
do n = 2*p, nmax, p
isprime(n) = .false.
end do
! One could use an array construct...
!where (mod(ia(2*p:), p) == 0)
! isprime(2*p:) = .false.
!end where
!isprime(2*p::p) = .false.
end do

! Results

do n = 2, nmax
print *, "n is prime: ", ia(n), isprime(n)
print *, "n is prime: ", n, isprime(n)
end do

print *, "Number of primes: ", count(isprime)
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