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Documentation Index

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Hardware API

The hardware module detects system specifications including CPU, RAM, GPU hardware, and inference backends.

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Core Types

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SystemSpecs

The main struct containing all detected hardware information: 
pub struct SystemSpecs {
    pub total_ram_gb: f64,
    pub available_ram_gb: f64,
    pub total_cpu_cores: usize,
    pub cpu_name: String,
    pub has_gpu: bool,
    pub gpu_vram_gb: Option<f64>,
    pub total_gpu_vram_gb: Option<f64>,
    pub gpu_name: Option<String>,
    pub gpu_count: u32,
    pub unified_memory: bool,
    pub backend: GpuBackend,
    pub gpus: Vec<GpuInfo>,
}
Key Fields:
  • total_ram_gb - Total system RAM in gigabytes
  • available_ram_gb - Currently available RAM (for model loading)
  • total_cpu_cores - Number of logical CPU cores
  • cpu_name - CPU model name string
  • has_gpu - Whether any GPU was detected
  • gpu_vram_gb - VRAM of primary GPU (per-card, not total)
  • total_gpu_vram_gb - Total VRAM across all same-model GPUs (for multi-GPU inference)
  • gpu_name - Primary GPU model name
  • gpu_count - Number of same-model GPUs (for multi-GPU setups)
  • unified_memory - Whether GPU and CPU share memory pool (Apple Silicon, AMD APUs)
  • backend - Primary inference backend for the system
  • gpus - All detected GPUs (may span multiple vendors)

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GpuBackend

The acceleration backend for inference: 
pub enum GpuBackend {
    Cuda,    // NVIDIA GPUs
    Metal,   // Apple Silicon
    Rocm,    // AMD GPUs with ROCm
    Vulkan,  // AMD/other GPUs without ROCm
    Sycl,    // Intel oneAPI
    CpuArm,  // ARM CPU (Apple, etc.)
    CpuX86,  // x86 CPU
    Ascend,  // Huawei Ascend NPUs
}
Methods: 
impl GpuBackend {
    pub fn label(&self) -> &'static str;
}
Returns human-readable label (“CUDA”, “Metal”, etc.).

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GpuInfo

Information about a single detected GPU: 
pub struct GpuInfo {
    pub name: String,
    pub vram_gb: Option<f64>,
    pub backend: GpuBackend,
    pub count: u32,              // >1 for multi-GPU
    pub unified_memory: bool,
}

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Functions

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SystemSpecs::detect()

Detects system hardware specifications: 
pub fn detect() -> Self
Returns: Complete system specifications Example: 
use llmfit_core::SystemSpecs;

let specs = SystemSpecs::detect();
println!("CPU: {} ({} cores)", specs.cpu_name, specs.total_cpu_cores);
println!("Total RAM: {:.2} GB", specs.total_ram_gb);
println!("Available RAM: {:.2} GB", specs.available_ram_gb);

if specs.has_gpu {
    if let Some(name) = &specs.gpu_name {
        println!("GPU: {}", name);
    }
    if let Some(vram) = specs.gpu_vram_gb {
        println!("VRAM: {:.2} GB", vram);
    }
    if specs.unified_memory {
        println!("Unified memory: GPU and CPU share RAM");
    }
}

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SystemSpecs::with_gpu_memory_override()

Override detected GPU VRAM (useful when detection fails): 
pub fn with_gpu_memory_override(self, vram_gb: f64) -> Self
Parameters:
  • vram_gb - VRAM amount in gigabytes
Returns: Updated SystemSpecs Example: 
let specs = SystemSpecs::detect()
    .with_gpu_memory_override(24.0);

assert_eq!(specs.gpu_vram_gb, Some(24.0));

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SystemSpecs::display()

Prints formatted system specifications: 
pub fn display(&self)
Example Output: 
=== System Specifications ===
CPU: Apple M4 Max (16 cores)
Total RAM: 128.00 GB
Available RAM: 102.40 GB
Backend: Metal
GPU: Apple M4 Max (unified memory, 128.00 GB shared, Metal)

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parse_memory_size()

Parses human-readable memory sizes: 
pub fn parse_memory_size(s: &str) -> Option<f64>
Parameters:
  • s - Size string (“32G”, “32GB”, “32000M”, etc.)
Returns: Size in gigabytes, or None if invalid Example: 
use llmfit_core::hardware::parse_memory_size;

assert_eq!(parse_memory_size("32G"), Some(32.0));
assert_eq!(parse_memory_size("32GB"), Some(32.0));
assert_eq!(parse_memory_size("16000M"), Some(15.625));
assert_eq!(parse_memory_size("1T"), Some(1024.0));

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gpu_memory_bandwidth_gbps()

Get memory bandwidth for known GPU models: 
pub fn gpu_memory_bandwidth_gbps(name: &str) -> Option<f64>
Parameters:
  • name - GPU model name
Returns: Memory bandwidth in GB/s, or None if unknown Example: 
use llmfit_core::hardware::gpu_memory_bandwidth_gbps;

// Known GPUs return bandwidth
assert_eq!(gpu_memory_bandwidth_gbps("RTX 4090"), Some(1008.0));
assert_eq!(gpu_memory_bandwidth_gbps("RTX 3090"), Some(936.0));
assert_eq!(gpu_memory_bandwidth_gbps("T4"), Some(320.0));

// Unknown GPUs return None
assert_eq!(gpu_memory_bandwidth_gbps("Custom GPU"), None);
This is used for accurate token/s estimation based on memory bandwidth limits.

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is_running_in_wsl()

Detects whether running in WSL (Windows Subsystem for Linux): 
pub fn is_running_in_wsl() -> bool
Returns: true if running in WSL, false otherwise Example: 
use llmfit_core::hardware::is_running_in_wsl;

if is_running_in_wsl() {
    println!("Running in WSL - GPU detection may require passthrough");
}

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GPU Detection Details

The hardware detection system uses platform-specific methods:

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NVIDIA GPUs

  1. nvidia-smi - Primary method via --query-gpu=memory.total,name
  2. sysfs - Fallback for containerized environments (/sys/class/drm/card*/device)
  3. Unified Memory Detection - Detects NVIDIA Grace Blackwell via addressing_mode field

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AMD GPUs

  1. rocm-smi - For systems with ROCm installed
  2. sysfs - For systems without ROCm (/sys/class/drm/card*/device)
  3. Unified APUs - Detects Ryzen AI MAX and AI 9/7/5 series with shared memory

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Apple Silicon

  • system_profiler SPDisplaysDataType - Detects M1/M2/M3/M4 series
  • Unified memory: Reports total system RAM as VRAM (same memory pool)

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Intel GPUs

  • sysfs - Detects Arc GPUs via vendor ID 0x8086
  • lspci - Fallback identification

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Windows

  • PowerShell - Get-CimInstance Win32_VideoController
  • wmic - Fallback for older Windows versions

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Multi-GPU Systems

For same-model multi-GPU setups: 
let specs = SystemSpecs::detect();

if specs.gpu_count > 1 {
    println!("Multi-GPU detected:");
    println!("  {} x {}", specs.gpu_count, specs.gpu_name.unwrap());
    println!("  Per-card VRAM: {:.2} GB", specs.gpu_vram_gb.unwrap());
    println!("  Total VRAM: {:.2} GB", specs.total_gpu_vram_gb.unwrap());
}
The total_gpu_vram_gb field is used for fit scoring since llama.cpp and vLLM support tensor splitting across multiple GPUs.

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Platform-Specific Notes

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macOS

On newer macOS versions (Tahoe+), available_ram_gb uses vm_stat as a fallback when sysinfo fails.

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Linux Containers

In containerized environments (Docker, Podman, Toolbx), GPU detection falls back to sysfs and uses flatpak-spawn --host lspci when needed.

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WSL

WSL environments are detected via WSL_INTEROP environment variable or /proc/version contents.

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