Tensorrt Optimization

import tensorrt as trt

# Create builder and network
logger = trt.Logger(trt.Logger.WARNING)
builder = trt.Builder(logger)
network = builder.create_network(
    1 << int(trt.NetworkDefinitionCreationFlag.EXPLICIT_BATCH))

# Parse ONNX model
parser = trt.OnnxParser(network, logger)
with open("model.onnx", "rb") as f:
    parser.parse(f.read())

# Configure builder
config = builder.create_builder_config()
config.set_memory_pool_limit(trt.MemoryPoolType.WORKSPACE, 1 << 30)  # 1GB

# Build engine
engine = builder.build_serialized_network(network, config)

# Save engine
with open("model.engine", "wb") as f:
    f.write(engine)

# Enable FP16
config.set_flag(trt.BuilderFlag.FP16)

# Enable INT8 (requires calibration)
config.set_flag(trt.BuilderFlag.INT8)

# Enable TF32 (Ampere+)
config.clear_flag(trt.BuilderFlag.TF32)  # Disable if needed

# Enable sparse tensor cores
config.set_flag(trt.BuilderFlag.SPARSE_WEIGHTS)

# Prefer precision per layer
config.set_flag(trt.BuilderFlag.PREFER_PRECISION_CONSTRAINTS)

# Force strict types
config.set_flag(trt.BuilderFlag.STRICT_TYPES)

class Calibrator(trt.IInt8EntropyCalibrator2):
    def __init__(self, data_loader, cache_file):
        super().__init__()
        self.data_loader = iter(data_loader)
        self.cache_file = cache_file
        self.batch_size = data_loader.batch_size
        self.device_input = cuda.mem_alloc(
            self.batch_size * 3 * 224 * 224 * 4)

    def get_batch_size(self):
        return self.batch_size

    def get_batch(self, names):
        try:
            batch = next(self.data_loader)
            cuda.memcpy_htod(self.device_input, batch.numpy())
            return [int(self.device_input)]
        except StopIteration:
            return None

    def read_calibration_cache(self):
        if os.path.exists(self.cache_file):
            with open(self.cache_file, "rb") as f:
                return f.read()
        return None

    def write_calibration_cache(self, cache):
        with open(self.cache_file, "wb") as f:
            f.write(cache)

# Use calibrator
calibrator = Calibrator(calibration_loader, "calibration.cache")
config.int8_calibrator = calibrator
config.set_flag(trt.BuilderFlag.INT8)

# Create optimization profile
profile = builder.create_optimization_profile()

# Define shape ranges [min, optimal, max]
profile.set_shape("input",
    min=(1, 3, 224, 224),     # Minimum shape
    opt=(8, 3, 224, 224),     # Optimal shape
    max=(32, 3, 224, 224))    # Maximum shape

config.add_optimization_profile(profile)

# Multiple profiles for different scenarios
profile_small = builder.create_optimization_profile()
profile_small.set_shape("input", (1, 3, 224, 224), (4, 3, 224, 224), (8, 3, 224, 224))
config.add_optimization_profile(profile_small)

profile_large = builder.create_optimization_profile()
profile_large.set_shape("input", (16, 3, 224, 224), (32, 3, 224, 224), (64, 3, 224, 224))
config.add_optimization_profile(profile_large)

# Load engine
runtime = trt.Runtime(logger)
with open("model.engine", "rb") as f:
    engine = runtime.deserialize_cuda_engine(f.read())

# Create execution context
context = engine.create_execution_context()

# Set input shape for dynamic shapes
context.set_input_shape("input", (batch_size, 3, 224, 224))

# Allocate buffers
inputs = []
outputs = []
bindings = []

for i in range(engine.num_io_tensors):
    name = engine.get_tensor_name(i)
    dtype = trt.nptype(engine.get_tensor_dtype(name))
    shape = context.get_tensor_shape(name)
    size = trt.volume(shape)

    buffer = cuda.mem_alloc(size * dtype.itemsize)
    bindings.append(int(buffer))

    if engine.get_tensor_mode(name) == trt.TensorIOMode.INPUT:
        inputs.append(buffer)
    else:
        outputs.append(buffer)

# Execute inference
cuda.memcpy_htod(inputs[0], input_data)
context.execute_v2(bindings)
cuda.memcpy_dtoh(output_data, outputs[0])

// Plugin class
class CustomPlugin : public nvinfer1::IPluginV2DynamicExt {
public:
    int getNbOutputs() const noexcept override { return 1; }

    nvinfer1::DimsExprs getOutputDimensions(
        int outputIndex,
        const nvinfer1::DimsExprs* inputs,
        int nbInputs,
        nvinfer1::IExprBuilder& exprBuilder) noexcept override {
        return inputs[0];  // Same shape as input
    }

    int enqueue(
        const nvinfer1::PluginTensorDesc* inputDesc,
        const nvinfer1::PluginTensorDesc* outputDesc,
        const void* const* inputs,
        void* const* outputs,
        void* workspace,
        cudaStream_t stream) noexcept override {
        // Launch custom CUDA kernel
        customKernel<<<blocks, threads, 0, stream>>>(
            inputs[0], outputs[0], inputDesc[0].dims);
        return 0;
    }
};

// Register plugin
REGISTER_TENSORRT_PLUGIN(CustomPluginCreator);

# Enable profiling
config.profiling_verbosity = trt.ProfilingVerbosity.DETAILED

# Use timing cache for faster builds
timing_cache_file = "timing.cache"
if os.path.exists(timing_cache_file):
    with open(timing_cache_file, "rb") as f:
        cache = config.create_timing_cache(f.read())
else:
    cache = config.create_timing_cache(b"")
config.set_timing_cache(cache, ignore_mismatch=False)

# Profile inference
profiler = trt.Profiler()
context.profiler = profiler

# Benchmark
import time
warmup = 10
iterations = 100

for _ in range(warmup):
    context.execute_v2(bindings)
cuda.Context.synchronize()

start = time.perf_counter()
for _ in range(iterations):
    context.execute_v2(bindings)
cuda.Context.synchronize()
end = time.perf_counter()

latency = (end - start) / iterations * 1000
throughput = batch_size * iterations / (end - start)
print(f"Latency: {latency:.2f} ms, Throughput: {throughput:.2f} samples/s")

# Use trtexec for analysis
trtexec --onnx=model.onnx \
    --fp16 \
    --workspace=4096 \
    --verbose \
    --dumpLayerInfo \
    --exportLayerInfo=layers.json

# Profile with Nsight Systems
nsys profile -o trt_profile \
    trtexec --loadEngine=model.engine --iterations=100

# View layer timing
trtexec --loadEngine=model.engine \
    --dumpProfile \
    --separateProfileRun

# Convert ONNX to TensorRT
trtexec --onnx=model.onnx --saveEngine=model.engine

# With FP16
trtexec --onnx=model.onnx --fp16 --saveEngine=model_fp16.engine

# With INT8 calibration
trtexec --onnx=model.onnx --int8 \
    --calib=calibration.cache --saveEngine=model_int8.engine

# Dynamic shapes
trtexec --onnx=model.onnx \
    --minShapes=input:1x3x224x224 \
    --optShapes=input:8x3x224x224 \
    --maxShapes=input:32x3x224x224 \
    --saveEngine=model_dynamic.engine

# Benchmark existing engine
trtexec --loadEngine=model.engine \
    --iterations=1000 \
    --warmUp=500 \
    --duration=10

{
  "operation": "build-engine",
  "status": "success",
  "input_model": "model.onnx",
  "output_engine": "model.engine",
  "configuration": {
    "precision": ["FP16", "INT8"],
    "workspace_mb": 1024,
    "dynamic_shapes": true
  },
  "optimization": {
    "layer_fusions": 23,
    "reformats_eliminated": 8,
    "tactics_selected": 156
  },
  "performance": {
    "build_time_s": 45.2,
    "engine_size_mb": 28.5,
    "estimated_latency_ms": 1.2
  }
}