device_capability.hpp

Go to the documentation of this file.

#pragma once
 
#include <compare>
#include <cstddef>
#include <cstdint>

namespace pulp::platform {
 
// ── Capability tier ────────────────────────────────────────────────────────

enum class DeviceCapabilityTier : std::uint8_t {
    Constrained = 0,
    Standard = 1,
    Full = 2,
};
 
inline constexpr std::size_t kDeviceCapabilityTierCount = 3;
 
// ── Thermal ladder ─────────────────────────────────────────────────────────

enum class ThermalState : std::uint8_t {
    Nominal = 0,
    Fair = 1,
    Serious = 2,
    Critical = 3,
};
 
inline constexpr std::size_t kThermalStateCount = 4;
 
// ── Observable inputs ──────────────────────────────────────────────────────

enum class PointerPrecision : std::uint8_t {
    Coarse = 0,
    Fine = 1,
};

struct DeviceCapabilityInputs {
    std::uint64_t usable_memory_bytes = 0;

    std::uint32_t usable_core_count = 0;

    bool thermal_reporting_available = false;

    bool realtime_render_available = false;

    PointerPrecision pointer_precision = PointerPrecision::Coarse;

    bool precision_keyboard_available = false;
 
    constexpr auto operator<=>(const DeviceCapabilityInputs&) const = default;
};
 
// ── Tier projection ────────────────────────────────────────────────────────

inline constexpr std::uint64_t kStandardTierMemoryBytes = 3ull * 1024 * 1024 * 1024;
inline constexpr std::uint64_t kFullTierMemoryBytes = 8ull * 1024 * 1024 * 1024;
inline constexpr std::uint32_t kStandardTierCoreCount = 4;
inline constexpr std::uint32_t kFullTierCoreCount = 8;
 
namespace detail {

[[nodiscard]] constexpr DeviceCapabilityTier
min_tier(DeviceCapabilityTier left, DeviceCapabilityTier right) {
    return left < right ? left : right;
}
 
} // namespace detail

[[nodiscard]] constexpr DeviceCapabilityTier
project_device_capability_tier(DeviceCapabilityInputs inputs) {
    const DeviceCapabilityTier by_memory =
        inputs.usable_memory_bytes >= kFullTierMemoryBytes      ? DeviceCapabilityTier::Full
        : inputs.usable_memory_bytes >= kStandardTierMemoryBytes ? DeviceCapabilityTier::Standard
                                                                 : DeviceCapabilityTier::Constrained;
 
    const DeviceCapabilityTier by_cores =
        inputs.usable_core_count >= kFullTierCoreCount      ? DeviceCapabilityTier::Full
        : inputs.usable_core_count >= kStandardTierCoreCount ? DeviceCapabilityTier::Standard
                                                             : DeviceCapabilityTier::Constrained;
 
    // No realtime render path caps the device at the review-and-perform rung,
    // whatever its memory and cores: the rungs above it are defined by being
    // able to render locally.
    const DeviceCapabilityTier by_realtime = inputs.realtime_render_available
                                                 ? DeviceCapabilityTier::Full
                                                 : DeviceCapabilityTier::Constrained;
 
    // Full-tier quotas assume the system will report heat so the consumer can
    // step down. Without that signal the top rung is not grantable.
    const DeviceCapabilityTier by_thermal_reporting = inputs.thermal_reporting_available
                                                          ? DeviceCapabilityTier::Full
                                                          : DeviceCapabilityTier::Standard;
 
    // The top rung is precision authoring, which presumes a precise pointer
    // and modifier keys. Neither bars authoring outright, so each caps at
    // Standard rather than Constrained.
    const DeviceCapabilityTier by_pointer = inputs.pointer_precision == PointerPrecision::Fine
                                                ? DeviceCapabilityTier::Full
                                                : DeviceCapabilityTier::Standard;
    const DeviceCapabilityTier by_keyboard = inputs.precision_keyboard_available
                                                 ? DeviceCapabilityTier::Full
                                                 : DeviceCapabilityTier::Standard;
 
    DeviceCapabilityTier tier = by_memory;
    tier = detail::min_tier(tier, by_cores);
    tier = detail::min_tier(tier, by_realtime);
    tier = detail::min_tier(tier, by_thermal_reporting);
    tier = detail::min_tier(tier, by_pointer);
    tier = detail::min_tier(tier, by_keyboard);
    return tier;
}
 
} // namespace pulp::platform