Error while converting Pytorch model to TensorRT

ERROR when trying to convert PyTorch model to TensorRT


I am trying to convert a segmentation model made in PyTorch to ONNX and then to TensorRT.
The segmentation model consists of a ‘efficientnet-b2’ encoder and a ‘FPN’ decoder (made with this repo

If I run this line of code (see below for steps to reproduce) i get the following error:

latency = compute_latency_ms_tensorrt('./model.onnx', (1, 3, 704, 1280))


[TensorRT] ERROR: Network must have at least one output
[TensorRT] ERROR: Network validation failed.
Traceback (most recent call last):
  File "", line 100, in <module>
    latency = compute_latency_ms_tensorrt('./model.onnx', (1, 3, 704, 1280))
  File "", line 89, in compute_latency_ms_tensorrt
    with build_engine("model.onnx") as engine:
AttributeError: __enter__

I tried to visualize the ONNX model with the Netron library whichs positively confirms there is a INPUT and OUTPUT.

I tried to solve the ERROR above by setting the output manually with this line of code after parsing the ONNX model:

with open(model_file, 'rb') as model:
            last_layer = network.get_layer(network.num_layers - 1)
            return builder.build_cuda_engine(network)

The ERROR now becomes:

python: ../builder/Network.cpp:1205: virtual nvinfer1::ILayer* nvinfer1::Network::getLayer(int) const: Assertion `layerIndex >= 0' failed.
Aborted (core dumped)

Any suggestions on how I can fix my TensorRT pipeline?

Thanks in advance,



TensorRT Version: 7.2.1
GPU Type: 2070 Super
Nvidia Driver Version: 455.23.04
CUDA Version: 11.1
CUDNN Version: 8.0.4
Operating System + Version: Ubuntu 20.04
Python Version (if applicable): 3.6.9
PyTorch Version (if applicable): 1.6.0
Baremetal or Container (if container which image + tag): docker pull

Steps To Reproduce

ONNX conversion:

model = torch.load('./model.pth')
model = model.cuda()

dummy_input = torch.randn(1, 3, 704, 1280, device='cuda')

torch.onnx.export(model, dummy_input, "model.onnx", input_names=["input"], output_names=["output"], verbose=True, opset_version=11)

TensorRT conversion:


TRT_LOGGER = trt.Logger(trt.Logger.VERBOSE)
DTYPE = trt.float32

# Model
INPUT_NAME = 'input'
OUTPUT_NAME = 'output'

def allocate_buffers(engine):
    h_input = cuda.pagelocked_empty(trt.volume(engine.get_binding_shape(0)), dtype=trt.nptype(DTYPE))
    h_output = cuda.pagelocked_empty(trt.volume(engine.get_binding_shape(1)), dtype=trt.nptype(DTYPE))
    d_input = cuda.mem_alloc(h_input.nbytes)
    d_output = cuda.mem_alloc(h_output.nbytes)
    return h_input, d_input, h_output, d_output

def build_engine(model_file):
    with trt.Builder(TRT_LOGGER) as builder, builder.create_network() as network, trt.OnnxParser(network, TRT_LOGGER) as parser:
        builder.max_workspace_size = MAX_WORKSPACE_SIZE
        builder.max_batch_size = MAX_BATCH_SIZE

        with open(model_file, 'rb') as model:
            return builder.build_cuda_engine(network)

def load_input(input_size, host_buffer):
    assert len(input_size) == 4
    b, c, h, w = input_size
    dtype = trt.nptype(DTYPE)
    img_array = np.random.randn(c, h, w).astype(dtype).ravel()
    np.copyto(host_buffer, img_array)

def do_inference(context, h_input, d_input, h_output, d_output, iterations=None):
    # Transfer input data to the GPU.
    cuda.memcpy_htod(d_input, h_input)
    # warm-up
    for _ in range(10):
        context.execute(batch_size=1, bindings=[int(d_input), int(d_output)])
    # test proper iterations
    if iterations is None:
        elapsed_time = 0
        iterations = 100
        while elapsed_time < 1:
            t_start = time.time()
            for _ in range(iterations):
                context.execute(batch_size=1, bindings=[int(d_input), int(d_output)])
            elapsed_time = time.time() - t_start
            iterations *= 2
        FPS = iterations / elapsed_time
        iterations = int(FPS * 3)
    # Run inference.
    t_start = time.time()
    for _ in tqdm(range(iterations)):
        context.execute(batch_size=1, bindings=[int(d_input), int(d_output)])
    elapsed_time = time.time() - t_start
    latency = elapsed_time / iterations * 1000
    return latency

def compute_latency_ms_tensorrt(model, input_size, iterations=None):
    with build_engine("model.onnx") as engine:
        h_input, d_input, h_output, d_output = allocate_buffers(engine)
        load_input(input_size, h_input)
        with engine.create_execution_context() as context:
            latency = do_inference(context, h_input, d_input, h_output, d_output, iterations=iterations)
    # FPS = 1000 / latency (in ms)
    return latency

Hi @michiel,
Can you please share your onnx model with us, so that we can help you better.

Hi @AakankshaS,

You can find the ONNX model on the following link:

Thanks in advance,


Hi @AakankshaS,

I am wondering if you found a solution to my conversion problem?

Thanks in advance,


Hi @michiel
The issue you are getting is a known gap between TRT and ONNX.
The fix will be available in future release.


is there any workround to fix this issue before the new release of TRT?