TLMHoang/custom_yolo_code_v2

Standalone YOLO Experiments For Varroa

This folder is independent from object_detection_related. It reads the original dataset layout directly:

train|val|test/
  videos/<video-id>/*.png
  labels/<video-id>/*.txt

Original labels contain a first count line, then absolute pixel xyxy boxes. The converter writes Ultralytics YOLO labels with class 0 = varroa.

Activate an environment with torch, ultralytics, and pillow installed:

conda activate ml2
python --version

If your shell cannot use conda activate, use conda run -n ml2 before the python command. The training and evaluation scripts default to device=cpu.

Prepare Dataset

Full conversion:

python yolo_related/prepare_dataset.py \
  --root . \
  --out-dir yolo_related/datasets/varroa_yolo

Small smoke dataset:

python yolo_related/prepare_dataset.py \
  --root . \
  --out-dir /tmp/varroa_yolo_smoke \
  --limit 2

Train

YOLOv8 baseline:

python yolo_related/train.py \
  --root . \
  --weights yolov8n.pt \
  --epochs 100 \
  --imgsz 640 \
  --batch-size 4 \
  --device cpu \
  --name yolov8n_varroa_cpu

YOLOv8 custom YAML with pretrained partial load:

python yolo_related/train.py \
  --root . \
  --model-yaml yolo_related/models/yolov8_varroa_custom.yaml \
  --pretrained yolov8n.pt \
  --epochs 100 \
  --imgsz 640 \
  --batch-size 4 \
  --device cpu \
  --name yolov8n_varroa_custom_cpu

YOLOv10 baseline, if your Ultralytics version supports the weight:

python yolo_related/train.py \
  --root . \
  --weights yolov10n.pt \
  --epochs 100 \
  --imgsz 640 \
  --batch-size 4 \
  --device cpu \
  --name yolov10n_varroa_cpu

Evaluate

python yolo_related/eval.py \
  --root . \
  --weights yolo_related/runs/train/yolov8n_varroa_cpu/weights/best.pt \
  --split test \
  --device cpu

Outputs:

• —yolo_related/runs/eval/<name>/test_per_image.csv
• —yolo_related/runs/eval/<name>/test_summary.csv

Local Ultralytics Clone

Custom YAML module names are resolved by Ultralytics internals, not by normal project imports. This repo uses a patched local clone:

yolo_related/ultralytics

yolo_related/train.py and yolo_related/eval.py call prefer_local_ultralytics() before importing ultralytics, so they use this clone automatically.

Manual one-liners do not use the clone unless you add it to PYTHONPATH:

PYTHONPATH=yolo_related/ultralytics \
python -c \
"import ultralytics; print(ultralytics.__file__)"

Expected path:

<repo>/yolo_related/ultralytics/ultralytics/__init__.py

If the path contains site-packages/ultralytics, your manual command is not using the patched clone and custom block names may fail with KeyError.

Current Custom Blocks

These blocks are already registered in the patched clone:

• —VarroaConvBlock
• —VarroaSEBlock

Registration locations:

• —yolo_related/ultralytics/ultralytics/nn/modules/block.py
• —yolo_related/ultralytics/ultralytics/nn/modules/__init__.py
• —yolo_related/ultralytics/ultralytics/nn/tasks.py

yolo_related/custom_blocks.py is only a readable reference copy. The YAML resolver uses the classes registered inside the local Ultralytics clone.

yolo_related/models/yolov8_varroa_custom.yaml currently uses a real custom block:

- [-1, 3, VarroaConvBlock, [128, 3, True]]

Step By Step: Replace A Block

Prefer replacement first because layer indices stay the same.

For YOLOv8, edit:

yolo_related/models/yolov8_varroa_custom.yaml

For YOLOv10, edit:

yolo_related/models/yolov10_varroa_custom.yaml

Original YOLOv8 line:

- [-1, 3, C2f, [128, True]]

Custom replacement:

- [-1, 3, VarroaConvBlock, [128, 3, True]]

Layer format:

[from, repeats, module, args]

For VarroaConvBlock, YAML args are:

[c2, kernel_size, shortcut]

Because VarroaConvBlock is in parse_model() base_modules, Ultralytics injects c1 from the previous layer and scales c2 according to the selected model scale.

What c1 And c2 Mean

Ultralytics modules usually use:

• —c1: input channels, inferred from the previous layer.
• —c2: output channels, written as the first value in YAML args.

You do not write c1 in the YAML for modules in base_modules. For this line:

- [-1, 3, VarroaConvBlock, [128, 3, True]]

Ultralytics reads:

from=-1, repeats=3, module=VarroaConvBlock, args=[128, 3, True]

Then parse_model() converts it to a constructor call like:

VarroaConvBlock(c1=previous_layer_channels, c2=scaled_128, kernel_size=3, shortcut=True)

With YOLOv8 nano scale, 128 is scaled by width multiplier 0.25, so the actual c2 becomes 32. That is why model printout can show:

Conv2d(32, 32, kernel_size=(3, 3), ...)

For blocks not in base_modules, Ultralytics does not inject c1/c2; you must handle their args manually in parse_model().

Step By Step: Insert A Block

Insert only after a replacement build works. Example after SPPF:

Edit the model YAML you are training, usually:

yolo_related/models/yolov8_varroa_custom.yaml

- [-1, 1, SPPF, [1024, 5]]
- [-1, 1, VarroaSEBlock, [1024, 8]]

For VarroaSEBlock, YAML args are:

[c2, reduction]

Warning: inserting a layer shifts later layer indices. Update downstream from references such as [-1, 9] or [15, 18, 21] when needed.

Step By Step: Add A New Block Class

For a new block named MyBlock:

1. 1.Add the class to yolo_related/ultralytics/ultralytics/nn/modules/block.py.
2. 2.Add "MyBlock" to block.py __all__.
3. 3.Import MyBlock in yolo_related/ultralytics/ultralytics/nn/modules/__init__.py.
4. 4.Add "MyBlock" to ultralytics/nn/modules/__init__.py __all__.
5. 5.Import MyBlock in yolo_related/ultralytics/ultralytics/nn/tasks.py.
6. 6.Add MyBlock to base_modules in parse_model() if its constructor starts with (c1, c2, ...).
7. 7.Add MyBlock to repeat_modules only if its constructor expects an internal repeat count n, like C2f(c1, c2, n, ...).
8. 8.Reference MyBlock in the model YAML you train, for example yolo_related/models/yolov8_varroa_custom.yaml.

Simple class shape:

class MyBlock(nn.Module):
    def __init__(self, c1: int, c2: int, kernel_size: int = 3):
        super().__init__()
        self.conv = nn.Conv2d(c1, c2, kernel_size, padding=kernel_size // 2)

    def forward(self, x):
        return self.conv(x)

YAML:

- [-1, 1, MyBlock, [256, 3]]

Ultralytics constructs it as:

MyBlock(c1=previous_layer_channels, c2=256, kernel_size=3)

Step By Step: Test After Editing

1. 1.Confirm the patched clone is active:

PYTHONPATH=yolo_related/ultralytics \
python -c \
"import ultralytics; print(ultralytics.__file__)"

1. 1.Build the model and print the edited layer:

PYTHONPATH=yolo_related/ultralytics \
python -c \
"from ultralytics import YOLO; m=YOLO('yolo_related/models/yolov8_varroa_custom.yaml'); print(m.model.model[2]); m.info(detailed=True)"

1. 1.Run a dummy forward:

PYTHONPATH=yolo_related/ultralytics \
python -c \
"import torch; from ultralytics import YOLO; m=YOLO('yolo_related/models/yolov8_varroa_custom.yaml'); y=m.model(torch.randn(1, 3, 640, 640)); print(type(y))"

1. 1.Check pretrained partial loading:

PYTHONPATH=yolo_related/ultralytics \
python -c \
"from ultralytics import YOLO; m=YOLO('yolo_related/models/yolov8_varroa_custom.yaml'); m.load('yolov8n.pt')"

Expected: a line like Transferred X/Y items from pretrained weights with X > 0. The exact numbers change when the architecture changes. Lower transfer counts are normal after replacing layers or changing channel shapes. The detect head often transfers partially or not at all because this dataset uses nc: 1 while COCO pretrained weights use nc: 80.

1. 1.Run a CPU smoke train:

python yolo_related/train.py \
  --root . \
  --yolo-dir /tmp/varroa_yolo_smoke \
  --model-yaml yolo_related/models/yolov8_varroa_custom.yaml \
  --pretrained yolov8n.pt \
  --epochs 1 \
  --imgsz 160 \
  --batch-size 2 \
  --device cpu \
  --workers 0 \
  --limit 2 \
  --project /tmp/varroa_yolo_runs \
  --name smoke_custom_block_cpu

Safe Editing Rules

• —Replace first, insert later.
• —Keep custom block output c2 compatible with the layer being replaced.
• —Change one block at a time, then run the test steps.
• —If inserting layers, update later from indices.
• —Keep Detect for YOLOv8 and v10Detect for YOLOv10 unchanged until simpler backbone/neck edits train cleanly.

Original YAML Files

Local patched clone:

yolo_related/ultralytics/ultralytics/cfg/models/v8/yolov8.yaml

Installed ml2 package:

python -c \
"import ultralytics, pathlib; root=pathlib.Path(ultralytics.__file__).parent; print(root/'cfg'/'models'/'v8'/'yolov8.yaml')"