Ёмкость TabM и контрольные точки обучения для прогноза доходности акций

# 07_tabular_dl.py


```py
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# %% [markdown]
# # Firm characteristics: a neural network under the objective that already failed
#
# [`06_gbm`](06_gbm.ipynb) varied the loss function on a fixed target and found that what the fit
# is asked to minimize separates the grid while capacity barely moves it. This notebook fits a
# neural network built for tabular data to the same targets, the same characteristics and the same
# folds - and it cannot repeat that experiment, because the shared TabM runner minimizes **squared
# error** on a regression target and cross-entropy on a classification one, and neither is a
# declared axis of the menu. The three configurations differ in capacity alone.
#
# So the comparison this notebook can make is the other one. Holding the objective fixed at the
# loss `06_gbm` identified as the poorly matched one, it varies:
#
# - **capacity**, across three presets that raise hidden width and ensemble membership together -
#   `tabm_s` at 64 units and 4 members, `tabm_m` at 128 and 8, `tabm_l` at 256 and 16;
# - **the amount of training**, because every configuration publishes a prediction set at each of
#   its declared epoch checkpoints rather than at the end of training only;
# - **the target**, because all three declared labels are fitted in one run - `fwd_ret_1m`,
#   its winsorized variant `fwd_ret_1m_win`, and the classification variant `fwd_class_1m`, whose
#   cross-entropy objective has no stake in the size of a tail return at all.
#
# **What TabM is.** A conventional deep ensemble trains several independent networks and averages
# them, which costs several networks. TabM keeps one shared backbone and gives each ensemble
# member a small adapter of its own - one learned scaling vector, applied to the backbone's output
# rather than inside it, so a member costs a row of parameters rather than a matrix. Each member
# also carries its own output head. The members train together in one forward pass and diverge
# only through those vectors, and averaging them cancels the part of each member's error that its
# own scaling made independent. `n_members` is how many adapters there are, and it is
# the axis that separates the three presets alongside hidden width.
#
# **Learning objectives**
#
# - Read a capacity grid whose objective is fixed by the runner rather than declared by the menu.
# - Use the epoch checkpoint as part of a configuration's identity rather than as something
#   resolved away by a validation metric.
# - See what a nonlinear model extracts from a monthly cross-section that a linear grid did not.
#
# **Book reference**: Chapter 12, Section 12.3 (Deep learning alternatives for tabular data).
# Chapter 6, Section 6.7 (Search accounting and run logging) introduces the run log this notebook
# writes into.
#
# **Prerequisites**: [`03_financial_features`](03_financial_features.ipynb),
# [`04_evaluation`](04_evaluation.ipynb), [`05_linear`](05_linear.ipynb), [`06_gbm`](06_gbm.ipynb).
#
# **What it writes**: one training run per configuration and label, and one complete validation
# prediction set per configuration, label and epoch checkpoint, in `run_log/registry.db` and under
# `run_log/training/` and `run_log/predictions/`, grouped under a named population.
# [`11_backtest`](11_backtest.ipynb) reads that population and selects on validation backtest
# Sharpe. **Selection happens there, not here**, and the checkpoint is part of what it selects.

# %%
"""Fit the declared firm-characteristics TabM population on the walk-forward folds."""

import plotly.graph_objects as go
import polars as pl
import yaml
from plotly.subplots import make_subplots

from case_studies.research import (
    declared_labels,
    load_model_configs,
    model_requests,
    narrows_declared_catalog,
    open_study,
    plan_models,
    planned_model_plan,
    primary_label,
    run_model_population,
    supersedes_for_run,
)
from utils.paths import get_case_study_dir
from utils.style import COLORS, show_plotly_with_alt

# %% tags=["parameters"]
LABELS: list[str] = []
EXECUTION_TIER = "canonical"
WORKSPACE: str = ""
PREVIEW_REDUCTIONS: dict = {}
CONFIG_NAMES: list[str] = []
POPULATION_NAME = ""
SUPERSEDES_POPULATION: str = ""
# The device to fit on. Empty means the one declared in config/setup.yaml.
DEVICE: str = ""

# %%
study = open_study(
    "us_firm_characteristics", execution_tier=EXECUTION_TIER, workspace=WORKSPACE or None
)

# %% [markdown]
# ## 1. Which labels, which models, and on what hardware
#
# Every label whose training menu declares `tabular_dl:` is fitted in this run, and all three do.
# `fwd_ret_1m` is the primary one, the total return over the month after the decision date;
# `fwd_ret_1m_win` is the same return with each month's cross-section clipped at its own tails;
# `fwd_class_1m` turns that return into a class. Each carries its own menu at
# `config/training/{label}.yaml`.

# %%
declared_labels(study, "tabular_dl")

# %% [markdown]
# The three presets live in `case_studies/config/tabm/` and raise hidden width and ensemble
# membership together, at a fixed dropout, a fixed batch size and a fixed epoch budget. Holding
# the training length fixed is what makes the grid a capacity comparison rather than a
# capacity-and-duration one, and the checkpoint dimension below is how the duration is examined
# separately.

# %%
configs = load_model_configs(
    study,
    "tabular_dl",
    labels=LABELS or None,
    config_names=CONFIG_NAMES or None,
)
configs

# %% [markdown]
# `LABELS` and `CONFIG_NAMES` both narrow what is fitted, and a narrowed run declares a different
# set of members than the canonical population does. A population is immutable once written, so
# such a run must publish under its own name: on a fresh workspace it would otherwise register an
# incomplete snapshot under the canonical one, and where the full population already exists the
# registry refuses it. The comparison is over `(label, config_name)` pairs rather than row counts,
# because a subset can match the canonical population on height while declaring different members.

# %%
if narrows_declared_catalog(study, "tabular_dl", configs) and not POPULATION_NAME:
    raise ValueError(
        f"this run fits {configs.height} of the declared label-configuration pairs, so it cannot "
        "publish the canonical population; pass POPULATION_NAME to give it its own"
    )

# %% [markdown]
# Two execution settings are declared in `config/setup.yaml` under `modeling.tabular_dl`, and both
# are part of a training identity rather than provenance beside it. A network's arithmetic depends
# on the device it runs on and on how many host threads reduce a batch, so a CUDA result and a CPU
# result of the same configuration are different computations and get different hashes. The runner
# refuses a device the machine does not have rather than falling back to one it does: silently
# substituting the fallback would publish a differently computed result under a declaration that
# says otherwise. A reader without an NVIDIA card passes `DEVICE="cpu"` and gets their own
# identities, which is the honest answer rather than a matching one. Because those identities are
# not the declared population's, the same rule as above applies: a run on any device other than
# the declared one must publish under its own `POPULATION_NAME`.

# %%
setup = yaml.safe_load(
    (get_case_study_dir("us_firm_characteristics") / "config" / "setup.yaml").read_text()
)
execution_settings = setup["modeling"]["tabular_dl"]
PUBLISHED_DEVICE = str(execution_settings["device"])
device = DEVICE or PUBLISHED_DEVICE

if device != PUBLISHED_DEVICE and not POPULATION_NAME:
    raise ValueError(
        f"this run fits on device {device!r} rather than the declared {PUBLISHED_DEVICE!r}, so "
        "it cannot publish the canonical population; pass POPULATION_NAME to give it its own"
    )

overrides = {
    "device": device,
    "num_threads": int(execution_settings["num_threads"]),
}
overrides

# %% [markdown]
# ## 2. Binding the declarations to the data
#
# Planning reads the label and feature files, computes the fold boundaries from the walk-forward
# parameters in `config/setup.yaml`, works out the exact rows each fit must predict, and derives
# every training and prediction identity - without fitting anything and without holding the
# prepared panel for each configuration at once. Configurations that read the same label share one
# materialization of it, so the panel is loaded once per label rather than once per configuration.
#
# Four things to check in the plan:
#
# - **`feature_count` and `eligible_rows` agree across every row of a label.** A row that differs
#   is a configuration measured on a different sample from its neighbours.
# - **`folds` is the same everywhere**, and equals the number of walk-forward splits
#   [`04_evaluation`](04_evaluation.ipynb) established.
# - **`validation_start` and `validation_end` bracket the development sample**, with none of the
#   held-out tail visible.
# - **`checkpoints` is the number of training states each configuration will publish predictions
#   for.** It comes from the preset's epoch budget and checkpoint interval, and multiplying it by
#   the number of rows gives the number of candidate models this notebook is about to create.

# %%
requests = model_requests(
    study,
    configs,
    execution_tier=EXECUTION_TIER,
    overrides=overrides,
    preview_reductions=PREVIEW_REDUCTIONS,
    notebook="07_tabular_dl",
)
plan = plan_models(study, requests=requests)

planned_model_plan(plan).select(
    "label",
    "config_name",
    "task",
    "feature_count",
    "eligible_rows",
    "folds",
    "checkpoints",
    "validation_start",
    "validation_end",
)

# %% [markdown]
# The plan is also the point at which a short population is visible. A run that fitted fewer
# label-configuration pairs than the menu declares would still print an IC table and still
# register its rows; what it would not do is announce the gap. Comparing the planned members
# against the frame loaded above catches it here, before anything is fitted.

# %%
planned_pairs = {(member.label, member.config_name) for member in plan.members}
requested_pairs = set(zip(configs["label"], configs["config_name"], strict=True))
if planned_pairs != requested_pairs:
    raise RuntimeError(
        "the plan does not match the loaded TabM menu; "
        f"missing {sorted(requested_pairs - planned_pairs)}, "
        f"unexpected {sorted(planned_pairs - requested_pairs)}"
    )
print(f"{len(requested_pairs)} label-configuration pairs")
print(f"{len(plan.expected_training_hashes)} training identities")
print(f"{len(plan.expected_prediction_hashes)} validation prediction sets")

# %% [markdown]
# ## 3. Fitting the population
#
# `run_model_population` runs every planned request. For one request it walks the folds, and on
# each one:
#
# 1. takes the rows inside that fold's training window,
# 2. fits a median imputer and a standardizer on those rows and applies them to the fold's
#    validation rows - a network needs a complete, comparably scaled design matrix, unlike the
#    trees in [`06_gbm`](06_gbm.ipynb) which route a missing value down their own branch,
# 3. trains the shared backbone and every member's adapter for the declared number of epochs,
#    saving the fitted state at each checkpoint on the way,
# 4. predicts the fold's validation rows from each saved state.
#
# Step 4 is what makes one fit produce many results. Fold predictions are concatenated into one
# series per checkpoint covering the whole validation period, and each becomes its own registered
# prediction set with its own identity. Nothing here chooses among them.
#
# **This notebook passes the plan rather than resolved requests, and that decides how the fitting
# is ordered.** There are two paths through `run_model_population`. Passing the plan hands the
# still-unresolved requests to the TabM batch runner, which groups the configurations reading the
# same label and prepares that label's folds once for all of them. Passing resolved requests
# instead fits one configuration at a time, each preparing its own folds - which is what
# [`05_linear`](05_linear.ipynb) and [`06_gbm`](06_gbm.ipynb) do, and they say so there.
#
# The trade is what the plan table above could show. Resolving first would have added
# `eligible_entities`, which needs the eligibility keys themselves; planning derives the same
# identities from the specification and cannot. Nine configurations holding nine prepared copies
# of a panel this size is the wrong side of that trade, and `eligible_rows` moves whenever the
# universe does, so the check the column existed for is still made.
#
# **What the call publishes is a population**: a named, immutable list of the prediction sets it
# will produce, written down before the first fit. Afterwards every member must exist and be
# complete, which is what makes the downstream comparison well defined.

# %%
population_name = POPULATION_NAME or "us_firm_characteristics-tabular_dl-validation-v1"
# The declared hash is only meaningful where a generation of this name already exists. A preview
# run, a reader's first canonical run against an empty `run_log/`, and a run under a caller-chosen
# `POPULATION_NAME` are all refused by `OfficialPopulation.create` if it is passed anyway. The
# resolution lives in shared code so no notebook branches on the tier.
supersedes = supersedes_for_run(
    study,
    population_name=population_name,
    declared=SUPERSEDES_POPULATION,
    execution_tier=EXECUTION_TIER,
)
execution, population = run_model_population(
    study, plan, population_name=population_name, supersedes=supersedes
)

# The runner's paths do not all record the same diagnostics, so the split below is printed only
# when every run recorded it. A TabM run that prepared folds carries `fitted_folds` and
# `reused_folds`; a configuration served whole from the registry records `reused` instead and no
# fold lists, because it prepared no folds and so has none to count. On a re-run every
# configuration is served that way, which is why the fallback line prints here rather than the
# split that [`05_linear`](05_linear.ipynb) and [`06_gbm`](06_gbm.ipynb) print. Indexing the keys
# raises `KeyError` on a registry hit, and defaulting them to zero is worse: it reports every fold
# as served from the registry, which is the opposite of what nothing-recorded means, and it does
# so in a number a reader cannot tell from a measurement.
with_folds = [item for item in execution.diagnostics if "fitted_folds" in item]
print(f"{len(execution.runs)} configurations, fitted or served from the registry")
if with_folds and len(with_folds) == len(execution.diagnostics):
    fitted = sum(len(item["fitted_folds"]) for item in with_folds)
    served = sum(len(item["reused_folds"]) for item in with_folds)
    print(f"folds fitted: {fitted}, folds served from the registry: {served}")
else:
    print(
        f"{len(with_folds)} of {len(execution.diagnostics)} runs recorded fold counts, "
        "so the fitted-against-served split is not reported"
    )
print(f"population {population.name}: {len(population.members)} prediction sets")

# %% [markdown]
# On a second run every configuration is served from the registry. Each identity is re-derived
# from the inputs, the registry already holds the matching rows, and the runner returns the
# stored result rather than fitting again - so re-running this notebook unchanged costs the time
# it takes to read the data rather than the time it took to fit.
#
# ### Running configurations of your own
#
# The published run log is read-only. To add runs, open the study against a workspace, which holds
# its own registry and artifacts and reads the same labels and features:
#
# ```python
# study = open_study("us_firm_characteristics", workspace="~/ml4t-experiments")
# configs = load_model_configs(study, "tabular_dl", labels=["fwd_ret_1m"], config_names=["tabm_s"])
# requests = model_requests(study, configs, overrides={"device": "cpu", "num_threads": 8})
# plan = plan_models(study, requests=requests)
# execution, population = run_model_population(study, plan, population_name="my-tabm-v1")
# ```
#
# `CONFIG_NAMES` fits a subset of what the menu declares. To fit something new, add a preset at
# `case_studies/config/tabm/tabm_xl.yaml` and list `tabm_xl` under `tabular_dl:` in the label's
# menu. Editing an existing preset changes that configuration's identity, so its result registers
# as a new row beside the old one rather than replacing it - and that includes `n_epochs` and
# `checkpoint_interval`, which decide the checkpoint surface as much as the architecture does.
# [`RUN_LOG.md`](../RUN_LOG.md#running-your-own-configurations) covers the rest.

# %% [markdown]
# ## 4. What came out
#
# One row per label, configuration and epoch checkpoint. `ic_mean` is the **information
# coefficient**: in each validation month, rank the firms by the model's prediction, rank them by
# the return they went on to earn, correlate the two rankings, and average that monthly
# correlation over the validation period.
#
# **Every count and every aggregate below is keyed on `(label, config_name)`, not on the
# configuration name alone.** The three presets are declared by all three labels, so grouping on
# the name would average a configuration's result across the targets it appears in and concatenate
# their learning curves into one line.
#
# The published catalog is checked against the population planned before fitting, rather than
# against its own row count: a run that lost a member would otherwise report a shorter table and
# nothing else.

# %% tags=["results"]
catalog = execution.catalog_rows.select(
    "config_name",
    "label",
    "task",
    "complete",
    "checkpoint_kind",
    "checkpoint_value",
    "ic_mean",
    "ic_std",
    "ic_n_days",
    "auc_mean_daily",
    "direction_label",
    "n_folds",
    "training_hash",
    "prediction_hash",
).sort(["label", "config_name", "checkpoint_value"])

if set(catalog.get_column("prediction_hash")) != set(plan.expected_prediction_hashes):
    raise RuntimeError("the published catalog differs from the population planned before fitting")
if catalog.filter(~pl.col("complete")).height:
    raise RuntimeError("a partial TabM checkpoint cannot pass to backtesting")
if catalog.select("label", "config_name", "checkpoint_value").n_unique() != catalog.height:
    raise RuntimeError("each label, configuration and checkpoint must identify one prediction set")
if catalog.get_column("checkpoint_value").null_count():
    raise RuntimeError("every TabM prediction must name the epoch it was taken at")

catalog = catalog.with_columns(
    full_coverage=pl.col("ic_n_days") == pl.col("ic_n_days").max().over("label")
)

primary = primary_label(study)
present = sorted(set(catalog.get_column("label")))
# The primary label leads when it was fitted. A subset run that leaves it out orders the panels by
# whichever label it did fit rather than by one that is not there.
panel_labels = [label for label in [primary] if label in present] + [
    label for label in present if label != primary
]
pairs = catalog.select("label", "config_name").unique().height
print(f"{catalog.height} candidate models: {pairs} label-configuration pairs")
print(f"at {catalog.n_unique('checkpoint_value')} checkpoints each, on {len(panel_labels)} labels")
catalog.select(
    "label",
    "config_name",
    "checkpoint_value",
    "ic_mean",
    "ic_std",
    "ic_n_days",
    "full_coverage",
).head(15)

# %% [markdown]
# ### The same three presets, on each target
#
# The characteristics and the folds are identical throughout, and all three labels declare the
# same three presets, so between these rows the only thing that changes is what is being predicted
# and - for the classification target alone - which loss the runner applies to it.
#
# `ic_mean` is defined for all three, which is what puts them on one axis. `auc_monthly` can be
# too, and `auc_scored_against` says what it was scored against: `fwd_class_1m` scores its own
# label and leaves that column null, while `fwd_ret_1m` has no classes of its own and is scored as
# a ranking signal against `fwd_class_1m`, the declared direction sibling of the same forward
# month. Those two rows are therefore comparable on that one number. `fwd_ret_1m_win` declares no
# sibling and carries no AUC; null there means not computed, not zero.

# %% tags=["results"]
by_label = (
    catalog.filter("full_coverage")
    .group_by("label")
    .agg(
        task=pl.col("task").first(),
        configurations=pl.col("config_name").n_unique(),
        candidates=pl.len(),
        scored_months=pl.col("ic_n_days").max(),
        best_ic=pl.col("ic_mean").max(),
        worst_ic=pl.col("ic_mean").min(),
        best_auc_monthly=pl.col("auc_mean_daily").max(),
        auc_scored_against=pl.col("direction_label").drop_nulls().first(),
    )
    .sort("best_ic", descending=True)
)
by_label

# %% [markdown]
# ### What more training does
#
# Each line traces one configuration's out-of-sample IC as epochs are added to it, inside its own
# target's panel. This is the figure the checkpoint dimension exists to produce, and the shape to
# read is where each line reaches its highest point.
#
# A line that rises and then flattens has learned what it is going to learn. A line still climbing
# at the last checkpoint has not converged at the declared training length, so its final number is
# a lower bound rather than a level. A line that peaks early and then falls is the third case, and
# it is the one this objective invites: squared error keeps spending later epochs on the firms
# whose returns are largest in magnitude, and a rank correlation counts each of those as one
# observation among thousands.

# %%
curves = catalog.filter("full_coverage").sort("label", "config_name", "checkpoint_value")
capacities = {
    "tabm_s": COLORS["blue"],
    "tabm_m": COLORS["amber"],
    "tabm_l": COLORS["copper"],
}


def capacity_color(name: str) -> str:
    """Return the declared preset's colour, refusing a name the palette does not cover.

    Defaulting would draw an unlisted preset in another one's colour under a legend saying the
    colour is the capacity setting, which is the one thing the figure claims.
    """
    try:
        return capacities[name]
    except KeyError as error:
        raise ValueError(f"{name!r} is not a declared TabM preset: {sorted(capacities)}") from error


# `shared_yaxes` matches axes across columns, so with one column it does nothing and each panel
# would be rescaled to fill itself. Matching every row to the first is what puts the targets on
# one vertical scale, which is what stacking them is for.
fig_curves = make_subplots(
    rows=len(panel_labels),
    cols=1,
    shared_xaxes=True,
    vertical_spacing=0.05,
    subplot_titles=[
        f"{label} ({'primary' if label == primary else 'variant'})" for label in panel_labels
    ],
)
drawn: set[str] = set()
for row, label in enumerate(panel_labels, start=1):
    panel = curves.filter(pl.col("label") == label)
    for config_name in panel.get_column("config_name").unique(maintain_order=True):
        series = panel.filter(pl.col("config_name") == config_name).sort("checkpoint_value")
        fig_curves.add_trace(
            go.Scatter(
                x=series.get_column("checkpoint_value").to_list(),
                y=series.get_column("ic_mean").to_list(),
                mode="lines+markers",
                name=config_name,
                legendgroup=config_name,
                showlegend=config_name not in drawn,
                line=dict(color=capacity_color(config_name), width=1.5),
                marker=dict(size=5),
            ),
            row=row,
            col=1,
        )
        drawn.add(config_name)
    fig_curves.add_hline(
        y=0, line_width=1, line_dash="dash", line_color=COLORS["neutral"], row=row, col=1
    )
    fig_curves.update_yaxes(title_text="Mean IC (validation)", row=row, col=1)
    if row > 1:
        fig_curves.update_yaxes(matches="y", row=row, col=1)
fig_curves.update_xaxes(title_text="Training epochs completed", row=len(panel_labels), col=1)
fig_curves.update_layout(
    title="Every capacity setting peaks at its earliest checkpoint",
    height=280 * len(panel_labels),
    width=1000,
    margin=dict(t=90),
    legend=dict(title_text="Capacity preset"),
)
# Where the lines peak is a fact about the frame, so the alt text counts it rather than asserting
# a shape the next run may not reproduce.
peaks = (
    curves.group_by("label", "config_name")
    .agg(
        peak_checkpoint=pl.col("checkpoint_value").sort_by("ic_mean", descending=True).first(),
        first_checkpoint=pl.col("checkpoint_value").min(),
        last_checkpoint=pl.col("checkpoint_value").max(),
    )
    .with_columns(
        peaks_at_the_start=pl.col("peak_checkpoint") == pl.col("first_checkpoint"),
        peaks_at_the_end=pl.col("peak_checkpoint") == pl.col("last_checkpoint"),
    )
)
peak_text = "; ".join(
    f"{row['label']}: {row['at_start']} of {row['total']} at the first checkpoint and "
    f"{row['at_end']} at the last"
    for row in peaks.group_by("label")
    .agg(
        total=pl.len(),
        at_start=pl.col("peaks_at_the_start").sum(),
        at_end=pl.col("peaks_at_the_end").sum(),
    )
    .sort("label")
    .iter_rows(named=True)
)
show_plotly_with_alt(
    fig_curves,
    "Line charts of mean validation information coefficient against the number of training epochs "
    "completed, one line per capacity preset - dark navy for tabm_s, gold for tabm_m, copper for "
    "tabm_l - with a marker at each declared epoch checkpoint. One panel per label on one shared "
    "pair of axes, each with a dashed zero line. Counted from the frame, the configurations whose "
    f"highest point is their first checkpoint against their last are {peak_text}.",
)

# %% [markdown]
# ### Whether capacity is what separates them
#
# The chart below drops the checkpoint dimension twice over, once at each end. The left bar of
# each pair is a configuration's IC at its first checkpoint and the right bar is its IC at its
# last, so every configuration is compared at the same two amounts of training and the gap between
# the pair is what the remaining epochs bought. Comparing capacity at a stopping point chosen
# after the fact would compare three configurations at three different training lengths.

# %%
edges = (
    curves.group_by("label", "config_name")
    .agg(
        first_ic=pl.col("ic_mean").sort_by("checkpoint_value").first(),
        last_ic=pl.col("ic_mean").sort_by("checkpoint_value").last(),
        first_checkpoint=pl.col("checkpoint_value").min(),
        last_checkpoint=pl.col("checkpoint_value").max(),
    )
    .sort("label", "config_name")
)
first_epoch = int(edges.get_column("first_checkpoint").max())
last_epoch = int(edges.get_column("last_checkpoint").max())

fig_capacity = make_subplots(
    rows=len(panel_labels),
    cols=1,
    shared_xaxes=True,
    vertical_spacing=0.05,
    subplot_titles=[
        f"{label} ({'primary' if label == primary else 'variant'})" for label in panel_labels
    ],
)
for row, label in enumerate(panel_labels, start=1):
    panel = edges.filter(pl.col("label") == label)
    order = [name for name in capacities if name in set(panel.get_column("config_name"))]
    panel = panel.with_columns(
        rank=pl.col("config_name").replace_strict(
            {name: index for index, name in enumerate(order)}, return_dtype=pl.Int32
        )
    ).sort("rank")
    for column, color, legend in (
        ("first_ic", COLORS["blue"], f"after {first_epoch} epochs"),
        ("last_ic", COLORS["neutral"], f"after {last_epoch} epochs"),
    ):
        fig_capacity.add_trace(
            go.Bar(
                x=panel.get_column("config_name").to_list(),
                y=panel.get_column(column).to_list(),
                marker_color=color,
                name=legend,
                legendgroup=legend,
                showlegend=row == 1,
            ),
            row=row,
            col=1,
        )
    fig_capacity.add_hline(
        y=0, line_width=1, line_dash="dash", line_color=COLORS["neutral"], row=row, col=1
    )
    fig_capacity.update_yaxes(title_text="Mean IC (validation)", row=row, col=1)
    if row > 1:
        fig_capacity.update_yaxes(matches="y", row=row, col=1)
fig_capacity.update_xaxes(
    title_text="Capacity preset, smallest first", row=len(panel_labels), col=1
)
fig_capacity.update_layout(
    title="Which axis moves the result depends on the target",
    height=280 * len(panel_labels),
    width=1000,
    margin=dict(t=90),
    barmode="group",
    legend=dict(title_text="Checkpoint"),
)
# Whether the gap within a pair beats the gap across presets is what the chart is for, and it
# differs by label, so the alt reads it rather than asserting one answer for all three.
within = (
    edges.with_columns(pair_gap=(pl.col("first_ic") - pl.col("last_ic")).abs())
    .group_by("label")
    .agg(
        median_pair_gap=pl.col("pair_gap").median(),
        across_presets=pl.col("last_ic").max() - pl.col("last_ic").min(),
    )
    .sort("label")
)
gap_text = "; ".join(
    f"{row['label']}: {'wider' if row['median_pair_gap'] > row['across_presets'] else 'narrower'}"
    for row in within.iter_rows(named=True)
)
show_plotly_with_alt(
    fig_capacity,
    "Grouped bar charts of mean validation information coefficient, one pair of bars per capacity "
    f"preset: dark navy for the first checkpoint at {first_epoch} epochs and neutral grey for the "
    f"last at {last_epoch}. One panel per label on one shared vertical scale, presets ordered "
    "smallest to largest, each panel carrying a dashed zero line. Counted from the frame, the "
    "median across presets of the gap between a preset's two bars, set against the spread across "
    f"presets at the last checkpoint, is {gap_text}. It is a median, so a single preset can run "
    "against the label's direction.",
)

# %% [markdown]
# The frame below is the claim the two charts make, computed rather than read off them. For each
# target it puts the range the checkpoint covers within a configuration against the range capacity
# covers across the grid at a fixed amount of training. Both are computed inside a target, because
# comparing a within-run range against a spread taken across targets would compare two different
# things.

# %% tags=["results"]
checkpoint_vs_capacity = (
    curves.group_by("label", "config_name")
    .agg(
        ic_min=pl.col("ic_mean").min(),
        ic_max=pl.col("ic_mean").max(),
    )
    .with_columns(checkpoint_range=pl.col("ic_max") - pl.col("ic_min"))
    .group_by("label")
    .agg(median_checkpoint_range=pl.col("checkpoint_range").median())
    .join(
        edges.group_by("label").agg(
            across_capacity_first=pl.col("first_ic").max() - pl.col("first_ic").min(),
            across_capacity_last=pl.col("last_ic").max() - pl.col("last_ic").min(),
        ),
        on="label",
    )
    .with_columns(
        checkpoint_dominates=pl.col("median_checkpoint_range")
        > pl.max_horizontal("across_capacity_first", "across_capacity_last")
    )
    .sort("label")
)
print(f"capacity compared at {first_epoch} and at {last_epoch} epochs")
checkpoint_vs_capacity

# %% [markdown]
# ## 5. What to notice
#
# **The objective is fixed here, and it is the one [`06_gbm`](06_gbm.ipynb) identified as the
# poorly matched one.** The shared runner minimizes squared error on a regression target, and the
# menu offers no alternative. That is a property of the implementation rather than a finding about
# TabM: a loss that weights an observation by the square of its error can be replaced, and the
# reason this notebook does not replace it is that doing so would change what the book's published
# TabM population is. Read the learning curves with that in mind - they are the behaviour of one
# objective at three capacities, not of the architecture in general.
#
# **The checkpoint is where the training length becomes visible, and it is registered rather than
# resolved.** A single end-of-training number cannot distinguish a configuration that converged
# from one that peaked early and decayed, and `checkpoint_vs_capacity` says which of the two axes
# moves the result further on each target. Where the checkpoint range exceeds the capacity spread,
# a comparison of the three presets at a stopping point chosen after the fact would be reporting
# where each training run happened to be rather than what its capacity bought.
#
# **The two regression targets are a controlled test of the same diagnosis.** `fwd_ret_1m_win` is
# `fwd_ret_1m` with each month's cross-section clipped at its own tails. If the extremes are what
# steers a squared-error fit away from the ranking, clipping them should change the shape of the
# curves rather than merely shifting them, and that is a directional prediction about two panels of
# the same figure - available only because one run fitted both.
#
# **The classification target is on a different objective entirely.** Cross-entropy on
# `fwd_class_1m` has no stake in how large a return was, only in which side of the cut it fell.
# `by_label` puts it on the same IC axis as the other two through the continuous return it was cut
# from, and on the same AUC axis as `fwd_ret_1m` through the direction sibling that label declares.
#
# **None of this selects anything.** IC measures whether predictions rank firms correctly, not
# whether a strategy trading them makes money after costs and turnover, and every checkpoint of
# every configuration stays in the published population for that reason. Selection is on validation
# backtest Sharpe in [`11_backtest`](11_backtest.ipynb), where the checkpoint is part of what is
# selected.
#
# **Known limitations.** The IC is an average of monthly rank correlations with no adjustment for
# serial dependence, so it is a diagnostic rather than a test, and it carries no interval that
# would say whether two presets differ. The grid varies capacity at a fixed dropout, a fixed
# learning-rate schedule and a fixed epoch budget, so it says nothing about what a tuned network
# would do - and the epoch budget is the one of those the curves let you see the cost of. Fold
# preprocessing imputes missing characteristics at the training fold's median, which is a value
# nobody observed, and the trees in [`06_gbm`](06_gbm.ipynb) did not need it. And every number is
# measured on validation folds that have been read many times over by the time a case study
# reaches this notebook.

# %% [markdown]
# **Next**: [`08_latent_factors`](08_latent_factors.ipynb) stops predicting the return directly and
# asks what small set of factors the 57 characteristics describe, then whether exposures to those
# factors carry the signal that the models fitted to the characteristics themselves have been
# looking for.

```