tursom/prime_numbers_c
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针对最为耗时的摸消3的倍数的操作进行了优化

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tursom 2019-05-04 19:09:34 +08:00
parent 7d138d7c36
commit 3f780c28b9
2 changed files with 23 additions and 8 deletions
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26
bit_set.c
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@ -33,14 +33,22 @@ size_t neededSize(unsigned long maxNumber) {
void getPrimeNumbers(unsigned long maxNumber, unsigned char *buffer) {
size_t needSize = neededSize(maxNumber);
unsigned long defaultValue = ~((unsigned long) 0);
for (unsigned long *k = ((unsigned long *) buffer) + (needSize >> 3) - 1; k >= (unsigned long *) buffer; --k) {
*k = defaultValue;
unsigned char arr[] = {219, 182, 109};
unsigned char initIndexArr[] = {1, 2, 0};
unsigned char initIndex = 0;
unsigned char *endP = buffer + needSize;
// 初始化缓冲区
for (unsigned char *k = buffer + 1; k < endP; ++k) {
*k = arr[initIndex];
initIndex = initIndexArr[initIndex];
}
*buffer = 0xfe;
*buffer = 0x6e;
// 进行计算
unsigned int sqrtMaxNumber = (unsigned int) sqrt(maxNumber) >> 1;
maxNumber >>= 1;
for (size_t i = 1; i <= sqrtMaxNumber; i++) {
for (size_t i = 2; i <= sqrtMaxNumber; i++) {
if (buffer[i >> 3] & 1 << (i & 7)) {
size_t doubleI = i + i + 1;
for (size_t j = (doubleI * doubleI) >> 1; j < maxNumber; j += doubleI) {
@ -48,8 +56,10 @@ void getPrimeNumbers(unsigned long maxNumber, unsigned char *buffer) {
}
}
}
needSize <<= 2;
for (int l = (maxNumber + 1) >> 1; l < needSize; l++) {
// 去除多余结果
needSize <<= 3;
for (int l = maxNumber; l < needSize; l++) {
buffer[l >> 3] &= ~(1 << (l & 7));
}
}
@ -87,7 +97,7 @@ char ByteCode(const unsigned char n) {
#pragma clang diagnostic push
#pragma ide diagnostic ignored "hicpp-signed-bitwise"
void printByteMap(const unsigned char n) {
void printByteMap(unsigned char n) {
printf("%d %d %d %d %d %d %d %d",
(n & 1) != 0, (n & 0x2) != 0, (n & 0x4) != 0, (n & 0x8) != 0,
(n & 0x10) != 0, (n & 0x20) != 0, (n & 0x40) != 0, (n & 0x80) != 0);

5
main.c
View File

@ -1,3 +1,6 @@
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunknown-pragmas"
#pragma ide diagnostic ignored "hicpp-signed-bitwise"
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
@ -149,3 +152,5 @@ int main(int argc, char *argv[]) {
free(buff);
return 0;
}
#pragma clang diagnostic pop