47 lines
1.3 KiB
Go
47 lines
1.3 KiB
Go
/*
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Copyright © 2025 filifa
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package lib
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/*
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TotientSieve computes totient(k) for k=1 to n, where totient is Euler's totient function. buflen sets the buffer length of the returned channel. Larger buffer lengths can result in better performance at the cost of higher memory usage.
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*/
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func TotientSieve(n uint, buflen uint) chan uint {
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totients := make([]uint, n)
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totients[0] = 0
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totients[1] = 1
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for i := uint(2); i < n; i++ {
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totients[i] = i - 1
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}
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ch := make(chan uint, buflen)
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go func() {
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defer close(ch)
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for i := uint(0); i < n; i++ {
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ch <- totients[i]
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if i == 0 || i == 1 || totients[i] != i-1 {
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continue
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}
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for j := 2 * i; j < n; j += i {
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totients[j] -= totients[j] / i
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}
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}
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}()
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return ch
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}
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