ExperimentResult

from llenergymeasure import ExperimentResult

Concept

ExperimentResult is the data structure returned by run_experiment and contained in StudyResult.experiments. It is a frozen Pydantic model produced once per measurement run, holding all metrics from that run directly.

ExperimentResult mirrors the on-disk result.json schema closely - the JSON on disk is produced by model.model_dump(mode="json") and shares the same field names and units. See Results schema for the full on-disk layout including manifest.json and timeseries.parquet.

ExperimentResult is almost always returned by the harness, not constructed by users.

---

Fields

Identity

Field	Type	Description
schema_version	str	Result schema version (current: "4.0").
experiment_id	str	Unique identifier for this experiment run.
measurement_config_hash	str	16-char SHA-256 hex of the ExperimentConfig (environment fields excluded). Matches the hash in the result directory name on disk.
llenergymeasure_version	str | None	Package version that produced this result.

Engine and model

Field	Type	Description
engine	str	Inference engine used: "transformers", "vllm", or "tensorrt".
engine_version	str | None	Engine version string for reproducibility (e.g. "4.47.0" for Transformers).
model_name	str	Model name or path used.

Measurement methodology

Field	Type	Description
measurement_methodology	"total" | "steady_state" | "windowed"	What was measured: the full run, the steady-state window after warmup, or an explicit time window.
steady_state_window	tuple[float, float] | None	(start_sec, end_sec) relative to inference start. The single-process path sets (0.0, inference_time_sec). None only when no inference window was recorded.

Core metrics

Field	Type	Units	Description
total_tokens	int	tokens	Total tokens generated during the run.
total_energy_j	float	joules	Total GPU energy for the run.
energy_adjusted_j	float | None	joules	Baseline-subtracted energy attributable to inference. None when no baseline was taken.
total_inference_time_sec	float	seconds	Wall time for the inference phase.
avg_tokens_per_second	float	tok/s	Throughput.
avg_energy_per_token_j	float	J/tok	Mean energy per token.
mj_per_tok_total	float | None	mJ/tok	Millijoules per token from total (unadjusted) energy.
mj_per_tok_adjusted	float | None	mJ/tok	Millijoules per token from baseline-adjusted energy. None when energy_adjusted_j is None.

FLOPs metrics

Field	Type	Description
total_flops	float	Estimated FLOPs. Derived from model config (reference metadata, not measured).
flops_per_output_token	float | None	FLOPs per decode token. None when total_flops=0 or output_tokens=0.
flops_per_input_token	float | None	FLOPs per prefill token. None when total_flops=0 or input_tokens=0.
flops_per_second	float | None	FLOPs throughput (total_flops / inference_time_sec). None when time=0 or flops=0.

Energy detail

Field	Type	Description
baseline_power_w	float | None	Idle GPU power in watts measured before the experiment. None when baseline measurement is disabled.
energy_per_device_j	list[float] | None	Per-GPU energy breakdown. Currently populated by the Zeus sampler only. None for NVML and CodeCarbon.
energy_breakdown	EnergyBreakdown | None	Detailed breakdown with baseline adjustment intervals.

Multi-GPU

Field	Type	Description
multi_gpu	MultiGPUMetrics | None	Multi-GPU aggregate metrics. None for single-GPU experiments.
aggregation	AggregationMetadata | None	Aggregation method and quality flags.

Quality and reproducibility

Field	Type	Description
measurement_warnings	list[str]	Quality warnings (e.g. short duration, thermal drift detected).
warmup_excluded_samples	int | None	Warmup iterations run before the measurement window (from warmup_result.iterations_completed). None when no warmup result is available.
reproducibility_notes	str	Fixed disclaimer about NVML measurement accuracy (+/- 5%).
thermal_throttle	ThermalThrottleInfo | None	GPU thermal and power throttle events during the run.
warmup_result	WarmupResult | None	Warmup convergence result (populated when CV convergence detection is enabled).

Timing

Field	Type	Description
start_time	datetime	Earliest process start time (UTC).
end_time	datetime	Latest process end time (UTC).

Sidecar

Field	Type	Description
timeseries	str | None	Relative filename of the timeseries Parquet sidecar (e.g. "timeseries.parquet"). None when timeseries saving is disabled.
latency_stats	LatencyStatistics | None	TTFT/ITL statistics from streaming inference. None for non-streaming engines.
extended_metrics	ExtendedEfficiencyMetrics | None	Extended efficiency metrics (TPOT, memory, GPU utilisation). Always present when the harness runs successfully; fields within are None when not computable.

---

Properties

ExperimentResult exposes two computed properties:

Property	Type	Description
duration_sec	float	Total experiment duration (end_time - start_time).
tokens_per_joule	float	Overall energy efficiency (total_tokens / total_energy_j). 0.0 when total_energy_j is zero.

---

Common patterns

Extract the headline efficiency metrics

result = run_experiment(model="gpt2", engine="transformers")

print(f"Energy (total):    {result.total_energy_j:.2f} J")
print(f"Energy (adjusted): {result.energy_adjusted_j or 'N/A'}")
print(f"mJ/tok (total):    {result.mj_per_tok_total:.3f}")
print(f"mJ/tok (adjusted): {result.mj_per_tok_adjusted or 'N/A'}")
print(f"Throughput:        {result.avg_tokens_per_second:.1f} tok/s")
print(f"FLOPs/s:           {result.flops_per_second or 'N/A'}")

Compare two results

a = run_experiment(model="gpt2", engine="transformers")
b = run_experiment(model="gpt2-medium", engine="transformers")

ratio = b.mj_per_tok_total / a.mj_per_tok_total
print(f"gpt2-medium is {ratio:.2f}x more expensive per token than gpt2")

Serialise to JSON

import json

with open("result.json", "w") as f:
    json.dump(result.model_dump(mode="json"), f, indent=2, default=str)

The on-disk result.json written by run_experiment / run_study uses this same serialisation. Loading it back:

data = json.loads(Path("results/study_name/001_c0_.../result.json").read_text())
loaded = ExperimentResult(**data)

Check for quality warnings

if result.measurement_warnings:
    for w in result.measurement_warnings:
        print(f"Warning: {w}")

if result.thermal_throttle and result.thermal_throttle.throttle_detected:
    print("Thermal throttling detected - results may be unreliable")

---

Pitfalls

energy_adjusted_j and mj_per_tok_adjusted are None when baseline is disabled. If measurement.baseline.enabled=False, neither field is populated. Always guard with if result.energy_adjusted_j is not None before using them.

energy_per_device_j is only populated by the Zeus sampler. With energy_sampler="nvml" or energy_sampler="codecarbon" (or "auto" resolving to either), energy_per_device_j is None; only the run-level total_energy_j is available.

extended_metrics fields can be None within an otherwise-present object. The ExtendedEfficiencyMetrics object is always attached but individual sub-fields (e.g. TTFT, memory bandwidth) are None when the data required to compute them was not available (non-streaming inference, no memory bandwidth counters, etc.).

flops_per_* are reference estimates, not measured values. FLOPs are estimated from model config (parameter count and sequence lengths) via AutoConfig, not from hardware counters. They are useful for relative comparisons but not for absolute roofline analysis.

Frozen model - no mutation. ExperimentResult has frozen=True. Attempting to set a field raises ValidationError. Use model_copy(update=...) to derive a modified copy.

---

See also

• run_experiment - the function that returns an ExperimentResult
• run_study - returns StudyResult containing list[ExperimentResult]
• Results schema - the on-disk result.json schema this mirrors