8. Creating Your MLPerfTiny Submission with microTVM

Authors: Mehrdad Hessar

This tutorial is showcasing building an MLPerfTiny submission using microTVM. This tutorial shows the steps to import a TFLite model from MLPerfTiny benchmark models, compile it with TVM and generate a Zephyr project which can be flashed to a Zephyr supported board to benchmark the model using EEMBC runner.

Install microTVM Python dependencies

TVM does not include a package for Python serial communication, so we must install one before using microTVM. We will also need TFLite to load models.

%%shell
pip install pyserial==3.5 tflite==2.1

import os
import pathlib
import tarfile
import tempfile
import shutil

Install Zephyr

%%shell
# Install west and ninja
python3 -m pip install west
apt-get install -y ninja-build

# Install ZephyrProject
ZEPHYR_PROJECT_PATH="/content/zephyrproject"
export ZEPHYR_BASE=${ZEPHYR_PROJECT_PATH}/zephyr
west init ${ZEPHYR_PROJECT_PATH}
cd ${ZEPHYR_BASE}
git checkout v3.2-branch
cd ..
west update
west zephyr-export
chmod -R o+w ${ZEPHYR_PROJECT_PATH}

# Install Zephyr SDK
cd /content
ZEPHYR_SDK_VERSION="0.15.2"
wget "https://github.com/zephyrproject-rtos/sdk-ng/releases/download/v${ZEPHYR_SDK_VERSION}/zephyr-sdk-${ZEPHYR_SDK_VERSION}_linux-x86_64.tar.gz"
tar xvf "zephyr-sdk-${ZEPHYR_SDK_VERSION}_linux-x86_64.tar.gz"
mv "zephyr-sdk-${ZEPHYR_SDK_VERSION}" zephyr-sdk
rm "zephyr-sdk-${ZEPHYR_SDK_VERSION}_linux-x86_64.tar.gz"

# Install python dependencies
python3 -m pip install -r "${ZEPHYR_BASE}/scripts/requirements.txt"

Note: Install CMSIS-NN only if you are interested to generate this submission using CMSIS-NN code generator.

Install CMSIS-NN

%%shell
CMSIS_SHA="51263182d16c92649a48144ba56c0945f9fce60e"
CMSIS_URL="http://github.com/ARM-software/CMSIS_5/archive/${CMSIS_SHA}.tar.gz"
export CMSIS_PATH=/content/cmsis
DOWNLOAD_PATH="/content/${CMSIS_SHA}.tar.gz"
mkdir ${CMSIS_PATH}
wget ${CMSIS_URL} -O "${DOWNLOAD_PATH}"
tar -xf "${DOWNLOAD_PATH}" -C ${CMSIS_PATH} --strip-components=1
rm ${DOWNLOAD_PATH}

CMSIS_NN_TAG="v4.0.0"
CMSIS_NN_URL="https://github.com/ARM-software/CMSIS-NN.git"
git clone ${CMSIS_NN_URL} --branch ${CMSIS_NN_TAG} --single-branch ${CMSIS_PATH}/CMSIS-NN

Import Python dependencies

import tensorflow as tf
import numpy as np

import tvm
from tvm import relay
from tvm.relay.backend import Executor, Runtime
from tvm.contrib.download import download_testdata
from tvm.micro import export_model_library_format
import tvm.micro.testing
from tvm.micro.testing.utils import (
    create_header_file,
    mlf_extract_workspace_size_bytes,
)

Import Visual Wake Word Model

To begin with, download and import the Visual Wake Word (VWW) TFLite model from MLPerfTiny. This model is originally from MLPerf Tiny repository. We also capture metadata information from the TFLite model such as input/output name, quantization parameters, etc. which will be used in following steps.

We use indexing for various models to build the submission. The indices are defined as follows: To build another model, you need to update the model URL, the short name and index number.

• Keyword Spotting(KWS) 1

• Visual Wake Word(VWW) 2

• Anomaly Detection(AD) 3

• Image Classification(IC) 4

If you would like to build the submission with CMSIS-NN, modify USE_CMSIS environment variable.

export USE_CMSIS=1

MODEL_URL = "https://github.com/mlcommons/tiny/raw/bceb91c5ad2e2deb295547d81505721d3a87d578/benchmark/training/visual_wake_words/trained_models/vww_96_int8.tflite"
MODEL_PATH = download_testdata(MODEL_URL, "vww_96_int8.tflite", module="model")

MODEL_SHORT_NAME = "VWW"
MODEL_INDEX = 2

USE_CMSIS = os.environ.get("TVM_USE_CMSIS", False)

tflite_model_buf = open(MODEL_PATH, "rb").read()
try:
    import tflite

    tflite_model = tflite.Model.GetRootAsModel(tflite_model_buf, 0)
except AttributeError:
    import tflite.Model

    tflite_model = tflite.Model.Model.GetRootAsModel(tflite_model_buf, 0)

interpreter = tf.lite.Interpreter(model_path=str(MODEL_PATH))
interpreter.allocate_tensors()
input_details = interpreter.get_input_details()
output_details = interpreter.get_output_details()

input_name = input_details[0]["name"]
input_shape = tuple(input_details[0]["shape"])
input_dtype = np.dtype(input_details[0]["dtype"]).name
output_name = output_details[0]["name"]
output_shape = tuple(output_details[0]["shape"])
output_dtype = np.dtype(output_details[0]["dtype"]).name

# We extract quantization information from TFLite model.
# This is required for all models except Anomaly Detection,
# because for other models we send quantized data to interpreter
# from host, however, for AD model we send floating data and quantization
# happens on the microcontroller.
if MODEL_SHORT_NAME != "AD":
    quant_output_scale = output_details[0]["quantization_parameters"]["scales"][0]
    quant_output_zero_point = output_details[0]["quantization_parameters"]["zero_points"][0]

relay_mod, params = relay.frontend.from_tflite(
    tflite_model, shape_dict={input_name: input_shape}, dtype_dict={input_name: input_dtype}
)

Defining Target, Runtime and Executor

Now we need to define the target, runtime and executor to compile this model. In this tutorial, we use Ahead-of-Time (AoT) compilation and we build a standalone project. This is different than using AoT with host-driven mode where the target would communicate with host using host-driven AoT executor to run inference.

# Use the C runtime (crt)
RUNTIME = Runtime("crt")

# Use the AoT executor with `unpacked-api=True` and `interface-api=c`. `interface-api=c` forces
# the compiler to generate C type function APIs and `unpacked-api=True` forces the compiler
# to generate minimal unpacked format inputs which reduces the stack memory usage on calling
# inference layers of the model.
EXECUTOR = Executor(
    "aot",
    {"unpacked-api": True, "interface-api": "c", "workspace-byte-alignment": 8},
)

# Select a Zephyr board
BOARD = os.getenv("TVM_MICRO_BOARD", default="nucleo_l4r5zi")

# Get the full target description using the BOARD
TARGET = tvm.micro.testing.get_target("zephyr", BOARD)

Compile the model and export model library format

Now, we compile the model for the target. Then, we generate model library format for the compiled model. We also need to calculate the workspace size that is required for the compiled model.

config = {"tir.disable_vectorize": True}
if USE_CMSIS:
    from tvm.relay.op.contrib import cmsisnn

    config["relay.ext.cmsisnn.options"] = {"mcpu": TARGET.mcpu}
    relay_mod = cmsisnn.partition_for_cmsisnn(relay_mod, params, mcpu=TARGET.mcpu)

with tvm.transform.PassContext(opt_level=3, config=config):
    module = tvm.relay.build(
        relay_mod, target=TARGET, params=params, runtime=RUNTIME, executor=EXECUTOR
    )

temp_dir = tvm.contrib.utils.tempdir()
model_tar_path = temp_dir / "model.tar"
export_model_library_format(module, model_tar_path)
workspace_size = mlf_extract_workspace_size_bytes(model_tar_path)

Generate input/output header files

To create a microTVM standalone project with AoT, we need to generate input and output header files. These header files are used to connect the input and output API from generated code to the rest of the standalone project. For this specific submission, we only need to generate output header file since the input API call is handled differently.

extra_tar_dir = tvm.contrib.utils.tempdir()
extra_tar_file = extra_tar_dir / "extra.tar"

with tarfile.open(extra_tar_file, "w:gz") as tf:
    create_header_file(
        "output_data",
        np.zeros(
            shape=output_shape,
            dtype=output_dtype,
        ),
        "include/tvm",
        tf,
    )

Create the project, build and prepare the project tar file

Now that we have the compiled model as a model library format, we can generate the full project using Zephyr template project. First, we prepare the project options, then build the project. Finally, we cleanup the temporary files and move the submission project to the current working directory which could be downloaded and used on your development kit.

input_total_size = 1
for i in range(len(input_shape)):
    input_total_size *= input_shape[i]

template_project_path = pathlib.Path(tvm.micro.get_microtvm_template_projects("zephyr"))
project_options = {
    "extra_files_tar": str(extra_tar_file),
    "project_type": "mlperftiny",
    "board": BOARD,
    "compile_definitions": [
        f"-DWORKSPACE_SIZE={workspace_size + 512}",  # Memory workspace size, 512 is a temporary offset
        # since the memory calculation is not accurate.
        f"-DTARGET_MODEL={MODEL_INDEX}",  # Sets the model index for project compilation.
        f"-DTH_MODEL_VERSION=EE_MODEL_VERSION_{MODEL_SHORT_NAME}01",  # Sets model version. This is required by MLPerfTiny API.
        f"-DMAX_DB_INPUT_SIZE={input_total_size}",  # Max size of the input data array.
    ],
}

if MODEL_SHORT_NAME != "AD":
    project_options["compile_definitions"].append(f"-DOUT_QUANT_SCALE={quant_output_scale}")
    project_options["compile_definitions"].append(f"-DOUT_QUANT_ZERO={quant_output_zero_point}")

if USE_CMSIS:
    project_options["compile_definitions"].append(f"-DCOMPILE_WITH_CMSISNN=1")

# Note: You might need to adjust this based on the board that you are using.
project_options["config_main_stack_size"] = 4000

if USE_CMSIS:
    project_options["cmsis_path"] = os.environ.get("CMSIS_PATH", "/content/cmsis")

generated_project_dir = temp_dir / "project"

project = tvm.micro.project.generate_project_from_mlf(
    template_project_path, generated_project_dir, model_tar_path, project_options
)
project.build()

# Cleanup the build directory and extra artifacts
shutil.rmtree(generated_project_dir / "build")
(generated_project_dir / "model.tar").unlink()

project_tar_path = pathlib.Path(os.getcwd()) / "project.tar"
with tarfile.open(project_tar_path, "w:tar") as tar:
    tar.add(generated_project_dir, arcname=os.path.basename("project"))

print(f"The generated project is located here: {project_tar_path}")

Use this project with your board

Now that we have the generated project, you can use this project locally to flash your board and prepare it for EEMBC runner software. To do this follow these steps:

tar -xf project.tar
cd project
mkdir build
cmake ..
make -j2
west flash

Now you can connect your board to EEMBC runner using this instructions and benchmark this model on your board.