84 lines
2.1 KiB
C
84 lines
2.1 KiB
C
/*
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* MEDIUM: Sequential Linked List Traversal
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* =========================================
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* This program creates a linked list with nodes allocated contiguously,
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* representing the best-case scenario for linked lists.
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* Still slower than arrays due to pointer chasing overhead.
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*
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* Compile: make list_sequential
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* Run: ./list_sequential
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* Profile: perf stat -e cache-misses,cache-references ./list_sequential
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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#define N 10000000 /* 10 million elements */
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struct node {
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int value;
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struct node *next;
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};
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double get_time(void) {
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struct timespec ts;
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clock_gettime(CLOCK_MONOTONIC, &ts);
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return ts.tv_sec + ts.tv_nsec / 1e9;
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}
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long sum_list(struct node *head) {
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long sum = 0;
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struct node *curr = head;
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while (curr != NULL) {
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sum += curr->value;
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curr = curr->next;
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}
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return sum;
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}
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/*
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* Create linked list with nodes allocated sequentially (best case for list)
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* All nodes allocated in one contiguous block, linked in order.
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*/
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struct node *create_list_sequential(int n) {
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struct node *nodes = malloc(n * sizeof(struct node));
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if (!nodes) {
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perror("malloc list");
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exit(1);
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}
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for (int i = 0; i < n - 1; i++) {
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nodes[i].value = i % 100;
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nodes[i].next = &nodes[i + 1];
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}
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nodes[n - 1].value = (n - 1) % 100;
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nodes[n - 1].next = NULL;
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return nodes;
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}
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int main(void) {
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printf("Sequential Linked List Traversal (%d elements)\n", N);
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printf("All nodes allocated contiguously - best case for linked list.\n");
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printf("Still has pointer chasing overhead vs array.\n\n");
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printf("Creating sequential linked list...\n");
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struct node *list = create_list_sequential(N);
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/* Warm up */
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sum_list(list);
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double start = get_time();
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long result = sum_list(list);
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double elapsed = get_time() - start;
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printf("Sequential list sum: %ld in %.4f seconds\n\n", result, elapsed);
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printf("To see cache behavior, run:\n");
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printf(" perf stat -e cache-misses,cache-references ./list_sequential\n");
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free(list);
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return 0;
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}
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