From 8a92d7642d2be25ffd57e6ad034c9dc2f1588a15 Mon Sep 17 00:00:00 2001
From: Wito Wiala <vitor.vieira@protonmail.com>
Date: Thu, 19 Feb 2026 15:41:05 +0000
Subject: [PATCH] Generalizing GPU framework to use Vulkan or CUDA with spirv

---
 src/utils/backend.rs | 147 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 147 insertions(+)
 create mode 100644 src/utils/backend.rs

diff --git a/src/utils/backend.rs b/src/utils/backend.rs
new file mode 100644
index 0000000..ec7c166
--- /dev/null
+++ b/src/utils/backend.rs
@@ -0,0 +1,147 @@
+use std::alloc::Layout;
+
+pub trait GpuAllocator: Send + Sync {
+    /// Allocate `size` bytes with given alignment.
+    /// Returns a host-mapped pointer.
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8;
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout);
+}
+
+/// CPU fallback — standard system allocator.
+pub struct SystemAllocator;
+
+impl Default for SystemAllocator {
+    fn default() -> Self {
+        Self
+    }
+}
+
+impl GpuAllocator for SystemAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        if layout.size() == 0 {
+            return layout.align() as *mut u8;
+        }
+        unsafe { std::alloc::alloc(layout) }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        if layout.size() > 0 {
+            unsafe {
+                std::alloc::dealloc(ptr, layout);
+            }
+        }
+    }
+}
+
+/// CUDA unified memory backend using CudaAllocator
+#[cfg(feature = "cuda")]
+pub struct CudaAllocator;
+
+#[cfg(feature = "cuda")]
+impl Default for CudaAllocator {
+    fn default() -> Self {
+        Self
+    }
+}
+
+#[cfg(feature = "cuda")]
+impl GpuAllocator for CudaAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        use cust::memory::cuda_malloc_unified;
+
+        let size = layout.size().max(layout.align());
+        if size == 0 {
+            return layout.align() as *mut u8;
+        }
+
+        let mut unified_ptr =
+            unsafe { cuda_malloc_unified::<u8>(size).expect("cuda_malloc_unified failed") };
+        let raw = unified_ptr.as_raw_mut();
+        std::mem::forget(unified_ptr);
+        raw
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        use cust::memory::{UnifiedPointer, cuda_free_unified};
+        if layout.size() > 0 {
+            let _ = unsafe { cuda_free_unified(UnifiedPointer::wrap(ptr)) };
+        }
+    }
+}
+
+/// Vulkan backend using gpu-allocator.
+#[cfg(feature = "vulkan")]
+pub mod vulkan {
+    use super::GpuAllocator;
+    use ash::vk;
+    use gpu_allocator::MemoryLocation;
+    use gpu_allocator::vulkan::{Allocation, AllocationCreateDesc, AllocationScheme, Allocator};
+    use parking_lot::Mutex;
+    use std::alloc::Layout;
+    use std::collections::HashMap;
+
+    pub struct VulkanAllocator {
+        allocator: Mutex<Allocator>,
+        /// Track pointer -> Allocation so we can free later.
+        allocations: Mutex<HashMap<usize, Allocation>>,
+    }
+
+    impl VulkanAllocator {
+        pub fn new(allocator: Allocator) -> Self {
+            Self {
+                allocator: Mutex::new(allocator),
+                allocations: Mutex::new(HashMap::new()),
+            }
+        }
+    }
+
+    impl Default for VulkanAllocator {
+        fn default() -> Self {
+            Self
+        }
+    }
+
+    impl GpuAllocator for VulkanAllocator {
+        unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+            let size = layout.size().max(layout.align());
+            if size == 0 {
+                return layout.align() as *mut u8;
+            }
+
+            let mut alloc = self.allocator.lock();
+            let allocation = alloc
+                .allocate(&AllocationCreateDesc {
+                    name: "arena",
+                    requirements: vk::MemoryRequirements {
+                        size: size as u64,
+                        alignment: layout.align() as u64,
+                        memory_type_bits: u32::MAX,
+                    },
+                    location: MemoryLocation::CpuToGpu,
+                    linear: true,
+                    allocation_scheme: AllocationScheme::GpuAllocatorManaged,
+                })
+                .expect("Vulkan allocation failed");
+
+            let ptr = allocation
+                .mapped_ptr()
+                .expect("Vulkan allocation not host-mapped")
+                .as_ptr() as *mut u8;
+
+            self.allocations.lock().insert(ptr as usize, allocation);
+            ptr
+        }
+
+        unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+            if layout.size() == 0 {
+                return;
+            }
+            if let Some(allocation) = self.allocations.lock().remove(&(ptr as usize)) {
+                self.allocator
+                    .lock()
+                    .free(allocation)
+                    .expect("Vulkan free failed");
+            }
+        }
+    }
+}