59 lines
1.1 KiB
Go
59 lines
1.1 KiB
Go
package primes
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type wheel struct {
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cache Cache
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elements []int64
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primes []int64
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size int64
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offset int
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n int64
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}
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func newWheel6(cache Cache) *wheel {
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return &wheel{cache, []int64{2, 4}, []int64{2, 3}, 6, 0, 5}
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}
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func (s *wheel) resetTo(n int64) {
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nn := n + 1
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s.n = (nn/s.size)*s.size - 1
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s.offset = 0
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for s.n+s.elements[s.offset] <= n {
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s.next()
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}
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}
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func (s *wheel) next() int64 {
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s.n += s.elements[s.offset]
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s.offset = (s.offset + 1) % len(s.elements)
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return s.n
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}
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func (s *wheel) expand() *wheel {
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prime := s.primes[len(s.primes)-1]
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it := NewIteratorFromCache(s.cache)
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for it.Next() && it.Get() <= prime {
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}
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prime = it.Get()
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if s.n <= prime {
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return nil
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}
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primes := append([]int64(nil), s.primes...)
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primes = append(primes, prime)
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var elements []int64
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var v int64 = -1
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var inc int64
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for i := int64(0); i < prime; i++ {
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for _, el := range s.elements {
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v += el
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inc += el
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if 0 != v%prime {
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elements = append(elements, inc)
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inc = 0
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}
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}
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}
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exp := &wheel{s.cache, elements, primes, s.size * prime, 0, s.n}
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exp.resetTo(s.n)
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return exp
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}
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