fix: apply Gemini review fixes (device kwarg, gradcheck requires_grad, torch prefix)

Review: Gemini 3.1 Pro approved. 3 fixes applied:
- pinn/SKILL.md: PchipFunction torch.tensor missing device=h.device (GPU crash)
- SKILL.md: gradcheck needs .requires_grad_(True) on doubled inputs
- SKILL.md: loss surface pseudocode now has torch. prefix + indexing='ij'
This commit is contained in:
wassname
2026-03-06 12:15:37 +08:00
parent 2db012dd2c
commit 463c8fdbbc
2 changed files with 7 additions and 7 deletions
+4 -4
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@@ -93,7 +93,7 @@ logger.log("grad_norm", grad_norm)
assert torch.isfinite(loss), f"Loss is {loss}" assert torch.isfinite(loss), f"Loss is {loss}"
# Verify custom gradients (use float64! relative error plummets from 1e-2 to 1e-8) # Verify custom gradients (use float64! relative error plummets from 1e-2 to 1e-8)
torch.autograd.gradcheck(my_custom_fn, inputs.double()) torch.autograd.gradcheck(my_custom_fn, inputs.double().requires_grad_(True))
``` ```
Gradient clipping *masks* problems -- always log the pre-clip norm to see if it's constantly being triggered. [CS231n: "the ratio of the update magnitudes to the value magnitudes... should be somewhere around 1e-3."] Gradient clipping *masks* problems -- always log the pre-clip norm to see if it's constantly being triggered. [CS231n: "the ratio of the update magnitudes to the value magnitudes... should be somewhere around 1e-3."]
@@ -340,9 +340,9 @@ When a loss isn't behaving as expected, don't guess -- visualize the loss surfac
```py ```py
# ── 2D loss surface with gradient quiver ────── # ── 2D loss surface with gradient quiver ──────
def analyze_component(loss_fn, x_range, y_range, n=80): def analyze_component(loss_fn, x_range, y_range, n=80):
xs = linspace(*x_range, n) xs = torch.linspace(*x_range, n)
ys = linspace(*y_range, n) ys = torch.linspace(*y_range, n)
X, Y = meshgrid(xs, ys) X, Y = torch.meshgrid(xs, ys, indexing='ij')
x_flat = X.flatten().requires_grad_(True) x_flat = X.flatten().requires_grad_(True)
y_flat = Y.flatten().requires_grad_(True) y_flat = Y.flatten().requires_grad_(True)
+3 -3
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@@ -281,13 +281,13 @@ For heat exchangers with phase change, the T(h) mapping from REFPROP/GERG-2008 m
def forward(ctx, h): def forward(ctx, h):
T = pchip_interp(h.detach().numpy()) # scipy T = pchip_interp(h.detach().numpy()) # scipy
ctx.save_for_backward(h) ctx.save_for_backward(h)
return torch.tensor(T, dtype=h.dtype) return torch.tensor(T, dtype=h.dtype, device=h.device)
@staticmethod @staticmethod
def backward(ctx, grad_output): def backward(ctx, grad_output):
h, = ctx.saved_tensors h, = ctx.saved_tensors
dTdh = pchip_interp.derivative()(h.detach().numpy()) # scipy dTdh = pchip_interp.derivative()(h.detach().cpu().numpy()) # scipy
return grad_output * torch.tensor(dTdh, dtype=h.dtype) return grad_output * torch.tensor(dTdh, dtype=h.dtype, device=h.device)
``` ```
5. Use float64 throughout. float32 loses precision near the phase boundary where dT/dh is small. 5. Use float64 throughout. float32 loses precision near the phase boundary where dT/dh is small.