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Just a exercise to count lines on text files using SSE
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| // gcc countlines.c -O2 -o countlines | |
| #include <stdio.h> | |
| #include <stdlib.h> | |
| #include <stdint.h> | |
| #include <unistd.h> | |
| #include <fcntl.h> | |
| #include <emmintrin.h> | |
| #define BLOCK_SIZE 4096 * 2 | |
| __always_inline | |
| int array_sum16(int8_t *array) | |
| { | |
| return array[0] | |
| + array[1] | |
| + array[2] | |
| + array[3] | |
| + array[4] | |
| + array[5] | |
| + array[6] | |
| + array[7] | |
| + array[8] | |
| + array[9] | |
| + array[10] | |
| + array[11] | |
| + array[12] | |
| + array[13] | |
| + array[14] | |
| + array[15]; | |
| } | |
| unsigned long long int count_block_lines(__m128i *block, ssize_t size) | |
| { | |
| static int8_t array_result[sizeof (__m128i)]; | |
| static int8_t array_lines[] = {'\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n'}; | |
| __m128i result; | |
| __m128i vector_lines = _mm_load_si128((__m128i *) array_lines); | |
| unsigned int block_index; | |
| unsigned long long int nlines = 0; | |
| int block_count = size / sizeof (__m128i); | |
| for (block_index = 0; block_index < block_count; block_index++) | |
| { | |
| result = _mm_cmpeq_epi8(vector_lines, block[block_index]); | |
| _mm_store_si128((__m128i *) array_result, result); | |
| nlines += -array_sum16(array_result); | |
| } | |
| int remaining_content_size = size % sizeof (__m128i); | |
| if (remaining_content_size == 0) | |
| { | |
| return nlines; | |
| } | |
| _mm_store_si128((__m128i *) array_result, block[block_index]); | |
| for (int i = 0; i < remaining_content_size; i++) | |
| { | |
| nlines += (array_result[i] == '\n'); | |
| } | |
| return nlines; | |
| } | |
| unsigned long long int count_file_lines(int fd) | |
| { | |
| static __m128i block[BLOCK_SIZE]; | |
| ssize_t buffer_size; | |
| unsigned long long int nlines = 0; | |
| while ((buffer_size = read(fd, block, BLOCK_SIZE)) > 0) | |
| { | |
| nlines += count_block_lines(block, buffer_size); | |
| } | |
| return nlines; | |
| } | |
| int main(int argc, char *argv[]) | |
| { | |
| if (argc < 2) | |
| { | |
| fputs("Usage: ./countlines <filepath>\n", stderr); | |
| return EXIT_SUCCESS; | |
| } | |
| int fd = open(argv[1], O_RDONLY); | |
| if (fd < 0) { | |
| perror("Error on open file"); | |
| return EXIT_FAILURE; | |
| } | |
| printf("%llu\n", count_file_lines(fd)); | |
| close(fd); | |
| return 0; | |
| } |
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