size_t
karmed_choose_best(struct karmed *p)
{
size_t head, i, j, best;
double mean, max;
if (p->k == 1)
return 0;
/*
* Bootstrap: choose the first lever that has not yet
* been tested.
*/
for (i = 0; i < p->k; i++) {
if (p->arms[i].effort == 0)
return i;
}
/*
* Exploration: choose a random lever.
*/
best = randinterval(0, p->k - 1);
/*
* Exploitation: choose the lever with the greatest
* expectation of reward.
*/
if (rand01() >= BANDIT_E_GREEDY) {
head = best;
max = 0;
for (j = 0; j < p->k; j++) {
i = (head + j) % p->k;
mean = p->arms[i].reward / p->arms[i].effort;
if (max < mean) {
best = i;
max = mean;
}
}
}
return best;
}
int main()
{
srand(1234);
val_t* xs = malloc(n * sizeof(val_t));
if (xs == NULL) {
fprintf(stderr, "Cannot allocate %zu bytes", n * sizeof(val_t));
return 1;
}
size_t i;
for (i = 0; i < n; ++i) {
xs[i] = randval();
}
vector_t* vec = vector_create(xs, n);
if (vec == NULL) {
fprintf(stderr, "Failed to create vector.");
return 1;
}
idx_t u, v;
for (i = 0; i < m; ++i) {
randinterval(n, &u, &v);
val_t true_sum = dense_sum(xs, u, v);
val_t sparse_sum = vector_sum(vec, u, v);
if (true_sum != sparse_sum) {
fprintf(stderr, "Incorrect sum.\n");
return 1;
}
}
vector_free(vec);
free(xs);
return 0;
}
