void
subset_points(point_t p[], const size_t n, const size_t k)
{
assert(monotonicity(p, n) == NON_MONOTONIC);
if(k == n) return;
assert(k <= n);
size_t max_idx = point_max_index(p, n);
if(max_idx != 1) {
/* Always keep the points before and after max_idx */
const size_t n_before = max_idx - 1;
const size_t s = n_before * sizeof(point_t);
point_t *buf = malloc(s);
memcpy(buf, p, s);
memmove(p, p + max_idx - 1, sizeof(point_t) * 3);
memcpy(p + 3, buf, s);
free(buf);
}
sort_by_like(p + 3, n - 3);
sort_by_t(p, k);
}
void
subset_points(point_t p[], const size_t n, const size_t k)
{
sort_by_t(p, n);
if (k == n) return;
assert(k < n);
curve_type_t curvature = classify_curve(p, n);
assert(curvature == CRV_ENC_MAXIMA || curvature == CRV_MONO_DEC);
if (curvature == CRV_MONO_DEC) {
/* Keep leftmost k - 1 points, which are already in place, and
* the rightmost point (for matching the asymptote). */
p[k - 1] = p[n - 1];
return;
}
/* Otherwise, the curvature is CRV_ENC_MAXIMA. Keep the maximum
* and its neighbors and sort the rest by likelihood. */
assert(n >= 3);
size_t max_idx = point_max_index(p, n);
if (max_idx > 1) {
const size_t n_before = max_idx - 1;
const size_t s = n_before * sizeof(point_t);
point_t *buf = malloc(s);
memcpy(buf, p, s);
memmove(p, p + max_idx - 1, sizeof(point_t) * 3);
memcpy(p + 3, buf, s);
free(buf);
}
if (k > 3) {
sort_by_like(p + 3, n - 3);
}
sort_by_t(p, k);
}
