Gahow Wang
224f750ee4
Var = Rc<RefCell<VarNode>> on a define-by-run tape: value + optional grad + parents + backward closure. backward() seeds a scalar loss, walks reverse topo order, and pushes grads to parents. push_grad always SUMs into the grad slot — the fan-out accumulation path T3 lacked. Per-crate build.rs emits the no_cuda cfg (does not propagate); engine gated, grad_check stays host-only. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
28 lines
930 B
Rust
28 lines
930 B
Rust
use std::env;
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use std::path::Path;
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use std::process::Command;
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// xtrain-autodiff's `Var` tape calls GPU ops (via xtrain-tensor), so it gates
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// those call sites behind `not(no_cuda)` — the same per-crate convention as
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// xtrain-cuda / xtrain-tensor (cfg does not propagate across crates). The
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// grad_check harness itself is host-only and always compiles. This script only
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// detects nvcc and emits the cfg; it compiles no CUDA.
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fn main() {
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println!("cargo:rustc-check-cfg=cfg(no_cuda)");
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let cuda_path = env::var("CUDA_HOME")
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.or_else(|_| env::var("CUDA_PATH"))
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.unwrap_or_else(|_| "/usr/local/cuda".to_string());
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if !nvcc_available(&cuda_path) {
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println!("cargo:rustc-cfg=no_cuda");
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}
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}
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fn nvcc_available(cuda_path: &str) -> bool {
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if Command::new("nvcc").arg("--version").output().is_ok() {
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return true;
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}
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Path::new(&format!("{cuda_path}/bin/nvcc")).exists()
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}
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