feat: Add json+cuda_ipc array encoding for GPU-direct tensor transfer

[dionhaefner]

Summary

• New cuda_ipc array encoding that passes CUDA IPC memory handles instead of serialized tensor bytes
• Framework-agnostic: works with any GPU array that implements __cuda_array_interface__ (PyTorch, CuPy, JAX, Numba)
• Uses ctypes calls to libcudart directly — no PyTorch or CuPy dependency in the encode path
• Decode path requires CuPy (returns cupy.ndarray); consumers convert via torch.as_tensor() or DLPack as needed
• Containers launched with json+cuda_ipc automatically get --ipc=host

What problem does this solve?

Tesseract's data path is CPU-bound. Array encoding serializes via JSON/base64/binref, and copies to CPU at every boundary. For tight composition loops (optimization, MCMC), the GPU→CPU→serialize→network→CPU→GPU round-trip dominates wall time.

With cuda_ipc, tensors stay on the GPU, while the CPU only handles metadata (like shape and dtype) – this is essentially binref for GPU memory.

Usage

# Container path
t = Tesseract.from_image("my_gpu_tesseract", gpus=["0"], output_format="json+cuda_ipc")
t.serve()
result = t.apply({"x": cupy_array})  # or torch tensor, or any __cuda_array_interface__ object

# Local path
t = Tesseract.from_tesseract_api("tesseract_api.py", output_format="json+cuda_ipc")

Requirements

• CUDA runtime (libcudart.so) on both producer and consumer
• CuPy for decoding (pip install cupy-cuda12x)
• --ipc=host for cross-container IPC (handled automatically by engine.py)
• Both processes must see the same physical GPU

[codecov]

Codecov Report

❌ Patch coverage is 22.40000% with 97 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.48%. Comparing base (04b7550) to head (67c3150).

Files with missing lines	Patch %	Lines
tesseract_core/runtime/array_encoding.py	21.35%	80 Missing and 1 partial ⚠️
tesseract_core/sdk/tesseract.py	31.25%	10 Missing and 1 partial ⚠️
tesseract_core/sdk/engine.py	0.00%	2 Missing and 1 partial ⚠️
tesseract_core/runtime/file_interactions.py	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #588      +/-   ##
==========================================
- Coverage   77.08%   75.48%   -1.61%     
==========================================
  Files          32       32              
  Lines        4487     4606     +119     
  Branches      738      760      +22     
==========================================
+ Hits         3459     3477      +18     
- Misses        725      822      +97     
- Partials      303      307       +4     

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[PasteurBot]

Benchmark Results

Benchmarks use a no-op Tesseract to measure pure framework overhead.

🚀 0 faster, ⚠️ 0 slower, ✅ 36 unchanged

✅ No significant performance changes detected.

Full results

Benchmark	Baseline	Current	Change	Status
api/apply_1,000	0.402ms	0.393ms	-2.2%	✅
api/apply_100,000	0.408ms	0.400ms	-1.9%	✅
api/apply_10,000,000	0.407ms	0.397ms	-2.5%	✅
cli/apply_1,000	1672.317ms	1648.496ms	-1.4%	✅
cli/apply_100,000	1702.285ms	1680.354ms	-1.3%	✅
cli/apply_10,000,000	1766.081ms	1730.622ms	-2.0%	✅
decoding/base64_1,000	0.027ms	0.027ms	-1.5%	✅
decoding/base64_100,000	0.751ms	0.758ms	+0.9%	✅
decoding/base64_10,000,000	139.384ms	139.584ms	+0.1%	✅
decoding/binref_1,000	0.170ms	0.172ms	+1.3%	✅
decoding/binref_100,000	0.262ms	0.264ms	+0.8%	✅
decoding/binref_10,000,000	27.732ms	28.095ms	+1.3%	✅
decoding/json_1,000	0.089ms	0.089ms	-0.0%	✅
decoding/json_100,000	8.255ms	8.280ms	+0.3%	✅
decoding/json_10,000,000	1116.804ms	1121.226ms	+0.4%	✅
encoding/base64_1,000	0.034ms	0.034ms	-0.7%	✅
encoding/base64_100,000	0.204ms	0.206ms	+0.7%	✅
encoding/base64_10,000,000	66.182ms	65.200ms	-1.5%	✅
encoding/binref_1,000	0.236ms	0.242ms	+2.2%	✅
encoding/binref_100,000	0.410ms	0.412ms	+0.5%	✅
encoding/binref_10,000,000	30.667ms	30.439ms	-0.7%	✅
encoding/json_1,000	0.117ms	0.119ms	+1.2%	✅
encoding/json_100,000	10.918ms	11.576ms	+6.0%	✅
encoding/json_10,000,000	1296.752ms	1317.191ms	+1.6%	✅
http/apply_1,000	2.856ms	2.910ms	+1.9%	✅
http/apply_100,000	8.743ms	9.234ms	+5.6%	✅
http/apply_10,000,000	930.312ms	941.730ms	+1.2%	✅
roundtrip/base64_1,000	0.071ms	0.070ms	-1.0%	✅
roundtrip/base64_100,000	1.122ms	1.127ms	+0.4%	✅
roundtrip/base64_10,000,000	206.272ms	208.074ms	+0.9%	✅
roundtrip/binref_1,000	0.421ms	0.418ms	-0.7%	✅
roundtrip/binref_100,000	0.661ms	0.662ms	+0.2%	✅
roundtrip/binref_10,000,000	59.083ms	59.370ms	+0.5%	✅
roundtrip/json_1,000	0.220ms	0.217ms	-1.1%	✅
roundtrip/json_100,000	18.543ms	17.888ms	-3.5%	✅
roundtrip/json_10,000,000	2413.511ms	2415.169ms	+0.1%	✅

• Runner: Linux 6.17.0-1010-azure x86_64