2021-07-09 Convert a Lightgbm dump

This example shows how to convert a lightgbm model dumped as a text file. It uses lightgbm to restore the model, converts it and checks the discrepencies.

import numpy
from numpy.testing import assert_almost_equal
import lightgbm
from onnxruntime import InferenceSession
from onnxmltools import convert_lightgbm
from skl2onnx.common.data_types import FloatTensorType

booster = lightgbm.Booster(model_file="model.txt")
n = booster.num_feature()

onx = convert_lightgbm(booster, initial_types=[('input', FloatTensorType([None, n]))])

sess = InferenceSession(onx.SerializeToString())
rnd = numpy.random.random((1, n)).astype(numpy.float32)

expected = booster.predict(rnd)
got = sess.run(None, {'input': rnd})[0]

assert_almost_equal(expected, got.ravel(), decimal=4)