我正在学习Tom Forsyth的线性速度顶点缓存优化，但不理解他如何计算ACMR。根据我读过的内容，我已经知道ACMR = 缓存未命中次数 / 三角形数量，但我不理解使用了什么类型的缓存（例如FIFO或LRU？）。
我编写了一个测试程序来计算和打印给定3D模型的ACMR，使用FIFO缓存，请问这段代码是否正确？或者我应该改用LRU缓存？
/* the number of entries in a FIFO cache */
#define FIFO_CACHE_SIZE 32
struct fifo_cache {
long entries[FIFO_CACHE_SIZE];
};
/**
* init_cache - initializes a FIFO cache
* @cache: A pointer to the FIFO cache structure to be initialized.
*
* Before a FIFO cache can be used, it must be initialized by calling this
* function.
*/
static void init_cache(struct fifo_cache *cache)
{
int i = 0;
/* initialize cache entries to an invalid value */
for (i = 0;i < FIFO_CACHE_SIZE;i++)
cache->entries[i] = -1;
}
/**
* check_entry - checks if the same entry is already added to the cache
* @cache: A pointer to the FIFO cache structure to be searched.
* @entry: An entry to be searched for.
*
* Return: If the same entry was found, the return value is nonzero. Otherwise,
* the return value is zero.
*/
static int check_entry(const struct fifo_cache *cache, u16 entry)
{
int i = 0;
for (i = 0;i < FIFO_CACHE_SIZE;i++) {
if (cache->entries[i] == (long)entry)
return 1;
}
return 0;
}
/**
* add_entry - adds a new entry to the FIFO cache
* @cache: A pointer to the FIFO cache structure the entry will be added to.
* @entry: An entry to add.
*/
static void add_entry(struct fifo_cache *cache, u16 entry)
{
long aux = 0;
long aux2 = 0;
int i = 0;
aux = cache->entries[0];
cache->entries[0] = (long)entry;
for (i = 1;i < FIFO_CACHE_SIZE;i++) {
aux2 = cache->entries[i];
cache->entries[i] = aux;
aux = aux2;
}
}
/**
* calculate_acmr - calculates the average cache miss ratio (aka. ACMR)
* @indices: The list of vertex indices.
* @count: The number of vertex indices in the @indices list.
*/
float calculate_acmr(const u16 *indices, size_t count)
{
struct fifo_cache cache = {0};
long total = 0; /* the total number of cache misses */
long i = 0;
/* initialize the cache */
init_cache(&cache);
for (i = 0;i < count;i++) {
if (!check_entry(&cache, indices[i])) {
/* an entry doesn't exist in the cache, so add it */
add_entry(&cache, indices[i]);
total++;
}
}
return ((float)total / (count / 3));
}