Quantization Tuning Workflow

When a model's quantized accuracy is lower than expected, DX-COM provides a tuning loop that lets you diagnose which regions are degrading accuracy and re-quantize with new settings without repeating the full compilation. This chapter covers the two features that make up that loop:

• Quantization Diagnosis (quant_diagnosis) — generates an HTML report of per-region quantization quality and a reusable .qxnn checkpoint.
• QXNN Resume — re-runs quantization from a .qxnn checkpoint, skipping the earlier compile phases.

Version Support

quant_diagnosis and QXNN Resume are available in DX-COM v2.4.0 and later. Both are accessible from the dxcom CLI and the dx_com Python API.

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The Diagnose → Resume Loop

Standard quantization tuning requires recompiling the model from ONNX every time you change a setting, which is slow. The diagnose → resume loop removes that cost:

Because the resume path reuses everything that does not depend on quantization, you can iterate over several calibration methods or Q-PRO settings quickly.

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Quantization Diagnosis (quant_diagnosis)

Enabling quant_diagnosis during compilation produces an HTML report that visualizes per-region quantization quality, flags high-severity regions, and includes ready-to-paste compile snippets for retrying with recommended settings. It also emits a .qxnn resume artifact so you can act on those recommendations without recompiling.

The option is self-contained — it does not require any other debug flag.

What is a region?

A region is a quantization block — a group of operations that are quantized and evaluated together as one unit during diagnosis. The report grades each region into a severity tier (OK / Warning / Critical) and reports region-level metrics (Cosine Similarity, QSNR) measured in isolation, which may not fully reflect deployed whole-model behavior.

The report contains three parts:

• Model Status — overall judgment (OK / Warning / Critical) with whole-model Cosine Similarity and QSNR.
• Candidate Recompile Intents — suggested next steps (e.g., a DXQ-P* scheme or a different calibration method), each with ready-to-paste Python API and dxcom CLI snippets.
• Evidence Summary — region severity distribution and weight/activation quantization details.

Reading the Report

Model Status gives the at-a-glance verdict. The status badge (here, Critical) is derived from the worse of the whole-model Cosine Similarity and QSNR, graded against the thresholds shown below it.

Candidate Recompile Intents lists the recommended next steps in priority order. Each intent comes with ready-to-paste Python API and dxcom CLI snippets that target the .qxnn checkpoint, so you can apply the suggestion directly via QXNN Resume. The candidate capabilities (e.g., DXQ-P3/P4/P5) are mutually-exclusive alternatives — pick one.

Evidence Summary (collapsible) backs the recommendations with the per-region severity distribution and weight/activation quantization details that the diagnosis is based on.

Usage

dxcom Command

dxcom \
  -m large_model.onnx \
  -c config.json \
  -o output/large_model \
  --quant_diagnosis

dx_com Python Module

import dx_com

dx_com.compile(
    model="large_model.onnx",
    output_dir="output/large_model",
    config="config.json",
    quant_diagnosis=True,
)

Output Files

quant_diagnosis creates a quant_diagnosis/ subdirectory under output_dir:

File	Description
quant_diagnosis/{model}.qxnn	Resume checkpoint consumed by QXNN Resume
quant_diagnosis/diagnosis_report.html	Per-region quantization quality report with retry snippets

note

The .qxnn checkpoint is always written when diagnosis runs; the HTML report is written on diagnosis success.

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QXNN Resume (Re-quantization Without Recompile)

QXNN Resume takes a .qxnn checkpoint and re-runs only the quantization-dependent stages (Quantization → Optimize → Codegen → SingleArtifact). The original ONNX model and config are not needed — the calibration settings are embedded in the checkpoint.

A .qxnn checkpoint is produced by quant_diagnosis (see above).

Selecting Resume Mode

QXNN resume mode is selected by passing a .qxnn checkpoint:

• CLI: --checkpoint <path>.qxnn
• Python: checkpoint="<path>.qxnn"

The checkpoint file extension must be .qxnn (case-insensitive); any other extension raises ValueError.

Usage

Re-calibrate with a different observer:

dxcom \
  --checkpoint output/large_model/quant_diagnosis/large_model.qxnn \
  -o output/large_model_iqr \
  --recalibration_method iqr

Enable automatic Q-PRO on resume:

dxcom \
  --checkpoint output/large_model/quant_diagnosis/large_model.qxnn \
  -o output/large_model_qpro \
  --use_q_pro

dx_com Python Module:

import dx_com

dx_com.compile(
    checkpoint="output/large_model/quant_diagnosis/large_model.qxnn",
    output_dir="output/large_model_iqr",
    recalibration_method="iqr",   # or: use_q_pro=True
)

Resume-Only Options

The following arguments apply only in QXNN resume mode (i.e., together with --checkpoint). Using them in standard compile mode raises an error.

CLI Option	Python Parameter	Description
--checkpoint	checkpoint	Path to the .qxnn resume artifact. Selects resume mode.
--recalibration_method	recalibration_method	Observer override for re-calibration. One of minmax, ema, iqr.
--enhanced_scheme	enhanced_scheme	Manual Q-PRO scheme selection (e.g., P3:num_samples=1024). Mutually exclusive with --use_q_pro.
--dataset_path	dataset_path	Override the calibration dataset path embedded in the checkpoint.

Constraints

• --checkpoint and -m/--model_path are mutually exclusive.
• --output_dir (-o) is required for resume.
• --use_q_pro and --enhanced_scheme are mutually exclusive.
• -c/--config_path is not required — on resume the calibration DataLoader is auto-built from the config embedded in the .qxnn (default loader only). Use --dataset_path to point at a different dataset.

Output Files

QXNN Resume writes the re-quantized model binary to output_dir:

• {checkpoint_stem}.dxnn — re-quantized model binary (filename defaults to the checkpoint stem; override with output_name).

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End-to-End Example

For a complete, step-by-step walkthrough of diagnosing a model and iterating on quantization settings, see the Use Case 6: Diagnose and Re-quantize Without Recompile section in Common Use Cases.

For the automatic Q-PRO quantization pipeline used during resume, see the Automatic Q-PRO (use_q_pro) section in Execution of DX-COM.