From 3298b777f6acd2e4b0ab37f4c8ca6809dc2cf3e6 Mon Sep 17 00:00:00 2001
From: rob-maron <132852777+rob-maron@users.noreply.github.com>
Date: Tue, 10 Mar 2026 21:48:51 -0400
Subject: [PATCH] cuda smoke test changes

---
 shared/client/src/state/init.rs     |  9 ++++
 shared/modeling/src/device_utils.rs | 69 +++++++++++++++++++++++++----
 2 files changed, 70 insertions(+), 8 deletions(-)

diff --git a/shared/client/src/state/init.rs b/shared/client/src/state/init.rs
index ec5d38d69..67bf23bd6 100644
--- a/shared/client/src/state/init.rs
+++ b/shared/client/src/state/init.rs
@@ -118,6 +118,9 @@ pub enum InitRunError {
     #[error("Unsupported architecture: {0}")]
     UnsupportedArchitecture(String),
 
+    #[error("Device is not usable: {0}")]
+    DeviceNotUsable(anyhow::Error),
+
     #[cfg(feature = "python")]
     #[error("Python distributed error: {0}")]
     PythonDistributedError(#[from] psyche_modeling::PythonDistributedCausalLMError),
@@ -193,6 +196,12 @@ impl RunInitConfigAndIO {
             ));
         }
 
+        // Fail fast if the device is not usable
+        init_config
+            .device
+            .ensure_usable()
+            .map_err(InitRunError::DeviceNotUsable)?;
+
         let model::Model::LLM(llm) = state.model;
 
         let hub_read_token = init_config.hub_read_token.clone();
diff --git a/shared/modeling/src/device_utils.rs b/shared/modeling/src/device_utils.rs
index 71a073f90..adf777890 100644
--- a/shared/modeling/src/device_utils.rs
+++ b/shared/modeling/src/device_utils.rs
@@ -1,9 +1,8 @@
 use std::{fmt, str::FromStr};
 
+use anyhow::Context;
 use itertools::Itertools;
-use tch::{Device, utils::has_mps};
-#[cfg(test)]
-use tch::{Kind, Tensor};
+use tch::{utils::has_mps, Device, Kind, Tensor};
 use thiserror::Error;
 
 /// Get all available CUDA devices
@@ -99,6 +98,22 @@ impl Devices {
             Devices::Mps => has_mps(),
         }
     }
+
+    /// Ensures the device is usable
+    ///
+    /// Currently does nothing for CPU and MPS devices
+    pub fn ensure_usable(&self) -> anyhow::Result<()> {
+        match self {
+            Devices::Cpu | Devices::Mps => Ok(()),
+            Devices::Cuda(device_indices) => {
+                for &device_idx in device_indices {
+                    ensure_cuda_device_usable(device_idx)
+                        .with_context(|| format!("cuda:{device_idx} is not usable"))?;
+                }
+                Ok(())
+            }
+        }
+    }
 }
 
 /// Get all available devices, for debugging purposes
@@ -217,6 +232,46 @@ impl DevicePytorchStr for Device {
     }
 }
 
+/// Ensures that a CUDA device is usable
+///
+/// The causal SDPA with a large sequence length is designed to trigger cuDNN's
+/// runtime kernel compilation
+fn ensure_cuda_device_usable(device_idx: usize) -> anyhow::Result<()> {
+    let device = Device::Cuda(device_idx);
+
+    let batch: i64 = 2;
+    let heads: i64 = 32;
+    let seq_len: i64 = 4096;
+    let head_dim: i64 = 128;
+
+    let q = Tensor::f_randn([batch, heads, seq_len, head_dim], (Kind::BFloat16, device))?
+        .f_set_requires_grad(true)
+        .context("failed to set requires grad")?;
+    let k = Tensor::f_randn([batch, heads, seq_len, head_dim], (Kind::BFloat16, device))?
+        .f_set_requires_grad(true)
+        .context("failed to set requires grad")?;
+    let v = Tensor::f_randn([batch, heads, seq_len, head_dim], (Kind::BFloat16, device))?
+        .f_set_requires_grad(true)
+        .context("failed to set requires grad")?;
+
+    let output = Tensor::f_scaled_dot_product_attention::<Tensor>(
+        &q, &k, &v, None,  // attn_mask
+        0.0,   // dropout_p
+        true,  // is_causal
+        None,  // scale (None = default 1/sqrt(head_dim))
+        false, // enable_gqa
+    )
+    .context("failed to run SDPA operation")?;
+
+    let loss = output
+        .f_sum(Kind::BFloat16)
+        .context("failed to sum SDPA output")?;
+    loss.f_backward()
+        .context("failed to run backward pass on SDPA output")?;
+
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use tch::utils::has_cuda;
@@ -242,11 +297,9 @@ mod tests {
                     .unwrap(),
                 Devices::Cuda((0..tch::Cuda::device_count() as usize).collect())
             );
-            assert!(
-                format!("cuda:{}", tch::Cuda::device_count())
-                    .parse::<Devices>()
-                    .is_err()
-            );
+            assert!(format!("cuda:{}", tch::Cuda::device_count())
+                .parse::<Devices>()
+                .is_err());
         } else {
             assert!(matches!(
                 "cuda".parse::<Devices>(),