diff --git a/docs/examples/plot_benchmark_tree.py b/docs/examples/plot_benchmark_tree.py
new file mode 100644
index 000000000..c0ca824b8
--- /dev/null
+++ b/docs/examples/plot_benchmark_tree.py
@@ -0,0 +1,372 @@
+"""
+.. _l-plot-optim-tree-ensemble:
+
+TreeEnsemble optimization
+=========================
+
+::
+
+    export PYTHONPATH=~/github/onnxruntime/build/linux_cpu/Release/:$PYTHONPATH
+
+"""
+
+import logging
+import os
+import timeit
+from typing import Tuple
+import numpy
+import onnx
+from onnx.helper import make_graph, make_model
+from onnx.reference import ReferenceEvaluator
+from pandas import DataFrame
+from sklearn.datasets import make_regression
+from sklearn.ensemble import RandomForestRegressor
+from skl2onnx import to_onnx
+from onnxruntime import InferenceSession, SessionOptions
+from onnx_array_api.plotting.text_plot import onnx_simple_text_plot
+from onnx_extended.reference import CReferenceEvaluator
+from onnx_extended.ortops.optim.cpu import get_ort_ext_libs
+from onnx_extended.ortops.optim.optimize import optimize_model
+from onnx_extended.tools.onnx_nodes import multiply_tree
+from onnx_extended.args import get_parsed_args
+from onnx_extended.ext_test_case import unit_test_going
+from onnx_extended.plotting.benchmark import hhistograms
+
+logging.getLogger("matplotlib.font_manager").setLevel(logging.ERROR)
+
+script_args = get_parsed_args(
+    "plot_benchmark_tree",
+    description=__doc__,
+    scenarios={
+        "SHORT": "short optimization (default)",
+        "LONG": "test more options",
+        "CUSTOM": "use values specified by the command line",
+    },
+    n_features=(2 if unit_test_going() else 5, "number of features to generate"),
+    n_trees=(3 if unit_test_going() else 10, "number of trees to train"),
+    max_depth=(2 if unit_test_going() else 5, "max_depth"),
+    batch_size=(1000 if unit_test_going() else 10000, "batch size"),
+    parallel_tree=("80,160,40", "values to try for parallel_tree"),
+    parallel_tree_N=("256,128,64", "values to try for parallel_tree_N"),
+    parallel_N=("100,50,25", "values to try for parallel_N"),
+    expose="",
+    n_jobs=("-1", "number of jobs to train the RandomForestRegressor"),
+)
+
+
+################################
+# Training a model
+# ++++++++++++++++
+
+
+def train_model(
+    batch_size: int, n_features: int, n_trees: int, max_depth: int
+) -> Tuple[str, numpy.ndarray, numpy.ndarray]:
+    filename = f"plot_op_tree_ensemble_optim-f{n_features}-{n_trees}-d{max_depth}.onnx"
+    if not os.path.exists(filename):
+        X, y = make_regression(
+            batch_size + max(batch_size, 2 ** (max_depth + 1)),
+            n_features=n_features,
+            n_targets=1,
+        )
+        print(f"Training to get {filename!r} with X.shape={X.shape}")
+        X, y = X.astype(numpy.float32), y.astype(numpy.float32)
+        # To be faster, we train only 1 tree.
+        model = RandomForestRegressor(
+            1, max_depth=max_depth, verbose=2, n_jobs=int(script_args.n_jobs)
+        )
+        model.fit(X[:-batch_size], y[:-batch_size])
+        onx = to_onnx(model, X[:1], target_opset={"": 18, "ai.onnx.ml": 3})
+
+        # And wd multiply the trees.
+        node = multiply_tree(onx.graph.node[0], n_trees)
+        onx = make_model(
+            make_graph([node], onx.graph.name, onx.graph.input, onx.graph.output),
+            domain=onx.domain,
+            opset_imports=onx.opset_import,
+            ir_version=onx.ir_version,
+        )
+
+        with open(filename, "wb") as f:
+            f.write(onx.SerializeToString())
+    else:
+        X, y = make_regression(batch_size, n_features=n_features, n_targets=1)
+        X, y = X.astype(numpy.float32), y.astype(numpy.float32)
+    Xb, yb = X[-batch_size:].copy(), y[-batch_size:].copy()
+    return filename, Xb, yb
+
+
+batch_size = script_args.batch_size
+n_features = script_args.n_features
+n_trees = script_args.n_trees
+max_depth = script_args.max_depth
+
+print(f"batch_size={batch_size}")
+print(f"n_features={n_features}")
+print(f"n_trees={n_trees}")
+print(f"max_depth={max_depth}")
+
+##############################
+# training
+
+filename, Xb, yb = train_model(batch_size, n_features, n_trees, max_depth)
+
+print(f"Xb.shape={Xb.shape}")
+print(f"yb.shape={yb.shape}")
+
+#######################################
+# Rewrite the onnx file to use a different kernel
+# +++++++++++++++++++++++++++++++++++++++++++++++
+#
+# The custom kernel is mapped to a custom operator with the same name
+# the attributes and domain = `"onnx_extended.ortops.optim.cpu"`.
+# We call a function to do that replacement.
+# First the current model.
+
+with open(filename, "rb") as f:
+    onx = onnx.load(f)
+print(onnx_simple_text_plot(onx))
+
+############################
+# And then the modified model.
+
+
+def transform_model(
+    model: onnx.ModelProto,
+    parallel_tree: int,
+    parallel_tree_N: int,
+    parallel_N: int,
+    first=-556,
+):
+    """
+    Modifies the graph.
+    Attributes is unused ``nodes_hitrates_as_tensor`` by the runtime so we use
+    that field to specify parallelization settings.
+
+    :param model: model proto serialized, the function makes a copy
+    :param parallel_tree: see https://github.com/microsoft/onnxruntime/blob/main/onnxruntime/core/providers/cpu/ml/tree_ensemble_common.h#L38
+    :param parallel_tree_N: see https://github.com/microsoft/onnxruntime/blob/main/onnxruntime/core/providers/cpu/ml/tree_ensemble_common.h#L39
+    :param parallel_N: see https://github.com/microsoft/onnxruntime/blob/main/onnxruntime/core/providers/cpu/ml/tree_ensemble_common.h#L40
+    :param first: -556 or -555, -556 makes onnxruntime prints out the parallelization
+        settings to make sure these are the expected values
+    :return: ModelProto
+    """
+    onx = onnx.ModelProto()
+    onx.ParseFromString(model.SerializeToString())
+    new_nodes = []
+    for node in onx.graph.node:
+        if node.op_type.startswith("TreeEnsemble"):
+            new_atts = []
+            for att in node.attribute:
+                if att.name.startswith("nodes_hitrates"):
+                    continue
+                new_atts.append(att)
+            new_atts.append(
+                onnx.helper.make_attribute(
+                    "nodes_hitrates_as_tensor",
+                    onnx.numpy_helper.from_array(
+                        numpy.array(
+                            [first, parallel_tree, parallel_tree_N, parallel_N],
+                            dtype=numpy.float32,
+                        ),
+                        name="nodes_hitrates_as_tensor",
+                    ),
+                )
+            )
+            del node.attribute[:]
+            node.attribute.extend(new_atts)
+            new_nodes.append(node)
+            continue
+        new_nodes.append(node)
+    del onx.graph.node[:]
+    onx.graph.node.extend(new_nodes)
+    del onx.opset_import[:]
+    onx.opset_import.extend(
+        [onnx.helper.make_opsetid("", 18), onnx.helper.make_opsetid("ai.onnx.ml", 3)]
+    )
+    return onx
+
+
+print("Tranform model to add a custom node.")
+onx_modified = transform_model(onx, 777, 778, 779)
+print(f"Save into {filename + 'modified.onnx'!r}.")
+with open(filename + "modified.onnx", "wb") as f:
+    f.write(onx_modified.SerializeToString())
+print("done.")
+print(onnx_simple_text_plot(onx_modified))
+
+#######################################
+# Comparing onnxruntime and the custom kernel
+# +++++++++++++++++++++++++++++++++++++++++++
+
+print(f"Loading {filename!r}")
+sess_ort = InferenceSession(filename, providers=["CPUExecutionProvider"])
+
+r = get_ort_ext_libs()
+print(f"Creating SessionOptions with {r!r}")
+opts = SessionOptions()
+if r is not None:
+    opts.register_custom_ops_library(r[0])
+
+print(f"Loading modified {filename!r}")
+sess_cus = InferenceSession(
+    onx_modified.SerializeToString(), opts, providers=["CPUExecutionProvider"]
+)
+
+print(f"Running once with shape {Xb.shape}.")
+base = sess_ort.run(None, {"X": Xb})[0]
+print(f"Running modified with shape {Xb.shape}.")
+got = sess_cus.run(None, {"X": Xb})[0]
+print("done.")
+
+#######################################
+# Discrepancies?
+
+d = numpy.abs(base - got)
+ya = numpy.abs(base).mean()
+print(f"Discrepancies: max={d.max() / ya}, mean={d.mean() / ya} (A={ya})")
+
+########################################
+# Simple verification
+# +++++++++++++++++++
+#
+# Baseline with onnxruntime.
+t1 = timeit.timeit(lambda: sess_ort.run(None, {"X": Xb}), number=50)
+print(f"baseline: {t1}")
+
+#################################
+# The custom implementation.
+t2 = timeit.timeit(lambda: sess_cus.run(None, {"X": Xb}), number=50)
+print(f"new time: {t2}")
+
+#################################
+# The same implementation but ran from the onnx python backend.
+ref = CReferenceEvaluator(filename)
+ref.run(None, {"X": Xb})
+t3 = timeit.timeit(lambda: ref.run(None, {"X": Xb}), number=50)
+print(f"CReferenceEvaluator: {t3}")
+
+#################################
+# The python implementation but from the onnx python backend.
+if n_trees < 50:
+    # It is usully slow.
+    ref = ReferenceEvaluator(filename)
+    ref.run(None, {"X": Xb})
+    t4 = timeit.timeit(lambda: ref.run(None, {"X": Xb}), number=5)
+    print(f"ReferenceEvaluator: {t4} (only 5 times instead of 50)")
+
+
+#############################################
+# Time for comparison
+# +++++++++++++++++++
+#
+# The custom kernel supports the same attributes as *TreeEnsembleRegressor*
+# plus new ones to tune the parallelization. They can be seen in
+# `tree_ensemble.cc <https://github.com/sdpython/onnx-extended/
+# blob/main/onnx_extended/ortops/optim/cpu/tree_ensemble.cc#L102>`_.
+# Let's try out many possibilities.
+# The default values are the first ones.
+
+if unit_test_going():
+    optim_params = dict(
+        parallel_tree=[40],  # default is 80
+        parallel_tree_N=[128],  # default is 128
+        parallel_N=[50, 25],  # default is 50
+    )
+elif script_args.scenario in (None, "SHORT"):
+    optim_params = dict(
+        parallel_tree=[80, 40],  # default is 80
+        parallel_tree_N=[128, 64],  # default is 128
+        parallel_N=[50, 25],  # default is 50
+    )
+elif script_args.scenario == "LONG":
+    optim_params = dict(
+        parallel_tree=[80, 160, 40],
+        parallel_tree_N=[256, 128, 64],
+        parallel_N=[100, 50, 25],
+    )
+elif script_args.scenario == "CUSTOM":
+    optim_params = dict(
+        parallel_tree=[int(i) for i in script_args.parallel_tree.split(",")],
+        parallel_tree_N=[int(i) for i in script_args.parallel_tree_N.split(",")],
+        parallel_N=[int(i) for i in script_args.parallel_N.split(",")],
+    )
+else:
+    raise ValueError(
+        f"Unknown scenario {script_args.scenario!r}, use --help to get them."
+    )
+
+cmds = []
+for att, value in optim_params.items():
+    cmds.append(f"--{att}={','.join(map(str, value))}")
+print("Full list of optimization parameters:")
+print(" ".join(cmds))
+
+##################################
+# Then the optimization.
+
+
+def create_session(onx):
+    return InferenceSession(onx.SerializeToString(), providers=["CPUExecutionProvider"])
+
+
+res = optimize_model(
+    onx,
+    feeds={"X": Xb},
+    transform=transform_model,
+    session=create_session,
+    baseline=lambda onx: InferenceSession(
+        onx.SerializeToString(), providers=["CPUExecutionProvider"]
+    ),
+    params=optim_params,
+    verbose=True,
+    number=script_args.number,
+    repeat=script_args.repeat,
+    warmup=script_args.warmup,
+    sleep=script_args.sleep,
+    n_tries=script_args.tries,
+)
+
+###############################
+# And the results.
+
+df = DataFrame(res)
+df.to_csv("plot_op_tree_ensemble_optim.csv", index=False)
+df.to_excel("plot_op_tree_ensemble_optim.xlsx", index=False)
+print(df.columns)
+print(df.head(5))
+
+################################
+# Sorting
+# +++++++
+
+small_df = df.drop(
+    [
+        "min_exec",
+        "max_exec",
+        "repeat",
+        "number",
+        "context_size",
+        "n_exp_name",
+    ],
+    axis=1,
+).sort_values("average")
+print(small_df.head(n=10))
+
+
+################################
+# Worst
+# +++++
+
+print(small_df.tail(n=10))
+
+
+#################################
+# Plot
+# ++++
+
+skeys = ",".join(optim_params.keys())
+title = f"TreeEnsemble tuning, n_tries={script_args.tries}\n{skeys}\nlower is better"
+ax = hhistograms(df, title=title, keys=("name",))
+fig = ax.get_figure()
+fig.savefig("plot_op_tree_ensemble_optim.png")
diff --git a/docs/tutorial/plot_dbegin_options_zipmap.py b/docs/tutorial/plot_dbegin_options_zipmap.py
index c478ae772..7ed22e072 100644
--- a/docs/tutorial/plot_dbegin_options_zipmap.py
+++ b/docs/tutorial/plot_dbegin_options_zipmap.py
@@ -26,7 +26,6 @@
 import onnxruntime as rt
 import onnx
 import skl2onnx
-from skl2onnx.common.data_types import FloatTensorType
 from skl2onnx import to_onnx
 from sklearn.linear_model import LogisticRegression
 from sklearn.multioutput import MultiOutputClassifier
diff --git a/pyproject.toml b/pyproject.toml
index cda762c49..4be1713cd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -41,7 +41,7 @@ select = [
     "C413", "C408", "C417",
     "E731",
     "PIE808",
-    "RUF012", "RUF015",
+    "RUF012", "RUF015", "RUF051",
     "SIM103", "SIM108", "SIM114", "SIM910",
     "UP006", "UP008", "UP015", "UP028", "UP030", "UP031", "UP035", "UP032"
 ]
@@ -53,8 +53,8 @@ select = [
     "B007", "B019", "B028", "B904",
     "C401", "C403", "C405", "C406", "C408", "C413", "C416", "C417",
     "PIE808", "PIE810",
-    "RUF005", "RUF012", "RUF010", "RUF015",
-    "SIM102", "SIM105", "SIM113", "SIM114", "SIM118", "SIM300",
+    "RUF005", "RUF012", "RUF010", "RUF015", "RUF046", "RUF051",
+    "SIM102", "SIM105", "SIM113", "SIM114", "SIM118", "SIM300", "SIM905",
     "UP015", "UP018", "UP028", "UP030", "UP031", "UP032"
 ]
 "tests_onnxmltools/**" = ["B028", "B904", "C403", "C408", "C413", "C417", "PIE808", "PIE810", "RUF010", "RUF015", "SIM102", "SIM105", "SIM118", "UP015", "UP028", "UP030", "UP031", "UP032"]