Add float scalar input support (#18751)

[digantdesai]

Summary:

The pybindings code handled bool and int scalar inputs but was missing
support for float (Python float → C++ double). This caused failures when
running models like Addmm that take float alpha/beta parameters, throwing
'Unsupported python type '.

Added py::isinstancepy::float_ handling to convert Python floats to
EValue(double) in both the portable and XNNPACK input processing paths.

Differential Revision: D99845426

[pytorch-bot]

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❌ 3 New Failures, 2 Unrelated Failures

As of commit 20d6e88 with merge base e638059 ():

NEW FAILURES - The following jobs have failed:

• pull / test-vulkan-operators-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 040be18b8de9d60878f2a3385535e59aeef57f1f79b344347e88c2f344e6579a /exec failed with exit code 56
• pull / unittest-editable / linux / linux-job (gh)
  RuntimeError: Command docker exec -t a73d5ff98d02971ace413df2a3fee6960fed6d7d470acbd485ead6e6da27b7d9 /exec failed with exit code 56
• Test ARM Backend / test-arm / test-backend-linux (arm_vgf_fp, operators) / linux-job (gh)
  RuntimeError: Command docker exec -t c1b1c34009b518db86bd0efe8061ade088e57f4ddedad1f404b218378f3c7c83 /exec failed with exit code 35

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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[Copilot]

Pull request overview

Adds Python float scalar input support to the ExecuTorch Python bindings by converting float → double and wrapping it in EValue, addressing runtime failures for exported models that take floating-point scalar parameters (e.g., alpha/beta).

Changes:

• Convert Python float inputs to EValue(double) in PyModule::run_method input processing.
• Convert Python float inputs to EValue(double) in PyMethod::set_inputs input processing.

Comments suppressed due to low confidence (2)

extension/pybindings/pybindings.cpp:815

• The exception message says inputs must be a flat list of tensors, but this code path explicitly supports non-tensor inputs (None/bool/int/float). Consider updating the message to reflect the actually supported scalar types to avoid confusing users when they pass an unsupported input type.

      } else {
        throw std::runtime_error(
            "Unsupported python type " + type_str +
            ". Ensure that inputs are passed as a flat list of tensors.");

extension/pybindings/pybindings.cpp:1145

• The exception message says inputs must be a flat list of tensors, but this conversion logic supports non-tensor inputs (None/bool/int/float). Consider updating the message to mention the supported scalar types to make debugging unsupported inputs clearer.

      } else {
        throw std::runtime_error(
            "Unsupported python type " + type_str +
            ". Ensure that inputs are passed as a flat list of tensors.");

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[meta-codesync]

@digantdesai has exported this pull request. If you are a Meta employee, you can view the originating Diff in D99845426.