Function sample_point_indices

src/framework/debug/trace.cpp:166–221

    oss << "]";
    return oss.str();
}

std::vector<size_t> sample_point_indices(size_t count, size_t target) {
    if (count == 0) {
        return {};
    }
    if (count <= target) {
        std::vector<size_t> all(count);
        for (size_t i = 0; i < count; ++i) {
            all[i] = i;
        }
        return all;
    }

    const size_t first_count = 14;
    const size_t middle_count = 12;
    const size_t last_count = 14;
    const size_t first_end = count / 3;
    const size_t middle_end = (count * 2) / 3;

    auto append_range = [](std::vector<size_t> & dst, size_t begin, size_t end, size_t samples) {
        if (begin >= end || samples == 0) {
            return;
        }
        const size_t span = end - begin;
        if (span <= samples) {
            for (size_t i = begin; i < end; ++i) {
                if (dst.empty() || dst.back() != i) {
                    dst.push_back(i);
                }
            }
            return;
        }
        for (size_t i = 0; i < samples; ++i) {
            const double pos = samples == 1 ? 0.0 : static_cast<double>(i) / static_cast<double>(samples - 1);
            const size_t offset = static_cast<size_t>(pos * static_cast<double>(span - 1));
            const size_t index = begin + offset;
            if (dst.empty() || dst.back() != index) {
                dst.push_back(index);
            }
        }
    };

    std::vector<size_t> points;
    points.reserve(target);
    append_range(points, 0, first_end, first_count);
    append_range(points, first_end, middle_end, middle_count);
    append_range(points, middle_end, count, last_count);

    if (points.empty() || points.front() != 0) {
        points.insert(points.begin(), 0);
    }
    if (points.back() != count - 1) {
        points.push_back(count - 1);
    }
    points.erase(std::unique(points.begin(), points.end()), points.end());
    return points;
}