Crate tenferro_capi 

C-API (FFI) for tenferro.

Exposes tensor lifecycle, einsum, SVD (including AD rules), and DLPack interop to host languages such as Julia, Python (JAX, PyTorch), and C/C++.

Design principles

• Opaque pointers: TfeTensorF64 is an opaque handle wrapping Tensor<f64>. Host languages never see Rust internals.
• Status codes: Every function takes a *mut tfe_status_t as its last argument. Rust panics are caught with catch_unwind and converted to TFE_INTERNAL_ERROR.
• Stateless AD rules: Only rrule (VJP) and frule (JVP) are exposed. The AD tape / TrackedTensor / DualTensor are Rust-internal and not exposed via FFI. Host languages manage their own AD tapes (ChainRules.jl, PyTorch autograd, JAX custom_vjp).
• f64 only in this POC phase. All functions carry the _f64 suffix.
• DLPack interop: Zero-copy tensor exchange with Julia, Python, and other frameworks via DLManagedTensorVersioned. Supports CPU and GPU memory. Use tfe_tensor_f64_to_dlpack (export) and tfe_tensor_f64_from_dlpack (import).
• Copy semantics for convenience functions: tfe_tensor_f64_from_data copies the caller’s data into a Rust-owned buffer. For zero-copy, use DLPack.

Memory ownership

Allocation	Freed by
Tensor from _from_data / _zeros / _clone	tfe_tensor_f64_release
Tensor from _from_dlpack	tfe_tensor_f64_release (calls DLPack deleter)
Output tensor (via **_out)	tfe_tensor_f64_release
Gradient tensor (rrule output)	tfe_tensor_f64_release
grads_out array (einsum rrule)	Caller provides buffer
Input data pointer	Caller (data is copied)
DLManagedTensorVersioned from _to_dlpack	Consumer calls deleter

Example (C pseudocode)

tfe_status_t status;
size_t shape[] = {3, 4};
double data[12] = { /* ... */ };

tfe_tensor_f64 *a = tfe_tensor_f64_from_data(data, 12, shape, 2, &status);
assert(status == TFE_SUCCESS);

const tfe_tensor_f64 *ops[] = {a, a};
tfe_tensor_f64 *c = tfe_einsum_f64("ij,jk->ik", ops, 2, &status);

tfe_tensor_f64_release(c);
tfe_tensor_f64_release(a);

Structs

DLDataType

DLPack data type descriptor.

DLDevice

DLPack device descriptor.

DLManagedTensorVersioned

DLPack managed tensor with version and ownership (DLPack v1.0+).

DLPackVersion

DLPack version information.

DLTensor

DLPack tensor descriptor (unmanaged).

TfeTensorF64

Opaque handle wrapping a Tensor<f64>.

Constants

DLPACK_FLAG_BITMASK_IS_COPIED

Data was copied (not zero-copy).

DLPACK_FLAG_BITMASK_READ_ONLY

Data is read-only (consumer must not write).

KDLCOMPLEX

Complex type code.

KDLCPU

CPU device.

KDLCUDA

NVIDIA CUDA GPU device memory.

KDLCUDA_HOST

Pinned CUDA CPU memory (cudaMallocHost).

KDLCUDA_MANAGED

CUDA managed/unified memory (cudaMallocManaged).

KDLFLOAT

Floating-point type code.

KDLINT

Integer type code.

KDLROCM

AMD ROCm GPU device memory.

KDLROCM_HOST

Pinned ROCm CPU memory (hipMallocHost).

TFE_INTERNAL_ERROR

Internal error (Rust panic or unexpected failure).

TFE_INVALID_ARGUMENT

Invalid argument (null pointer, bad subscript string, etc.).

TFE_SHAPE_MISMATCH

Tensor shape mismatch for the requested operation.

TFE_SUCCESS

Operation completed successfully.

Functions

tfe_einsum_f64^⚠

Execute einsum using string notation.

tfe_einsum_frule_f64^⚠

Forward-mode rule (JVP) for einsum.

tfe_einsum_rrule_f64^⚠

Reverse-mode rule (VJP) for einsum.

tfe_svd_f64^⚠

Compute the SVD of a tensor.

tfe_svd_frule_f64^⚠

Forward-mode rule (JVP) for SVD.

tfe_svd_rrule_f64^⚠

Reverse-mode rule (VJP) for SVD.

tfe_tensor_f64_clone^⚠

Deep-copy a tensor.

tfe_tensor_f64_data^⚠

Return a pointer to the tensor’s raw data buffer.

tfe_tensor_f64_from_data^⚠

Create a tensor from caller-provided data (copy semantics).

tfe_tensor_f64_from_dlpack^⚠

Import a DLPack managed tensor as a tenferro tensor (zero-copy).

tfe_tensor_f64_len^⚠

Return the total number of elements in the tensor.

tfe_tensor_f64_ndim^⚠

Return the number of dimensions (rank) of the tensor.

tfe_tensor_f64_release^⚠

Release (free) a tensor.

tfe_tensor_f64_shape^⚠

Write the shape of the tensor into the caller-provided buffer.

tfe_tensor_f64_to_dlpack^⚠

Export a tensor as a DLPack managed tensor (zero-copy).

tfe_tensor_f64_zeros^⚠

Create a tensor filled with zeros.

Type Aliases

tfe_status_t

Status code type returned by all C-API functions.