add group norm

Summary: Add GroupNorm support to master Detectron.

Reviewed By: rbgirshick

Differential Revision: D7611892

fbshipit-source-id: dc4fb84a0e2167b05fd8a94ee0ff1ab1c21369b7

configs/04_2018_gn_baselines/e2e_mask_rcnn_R-101-FPN_2x_gn.yaml

+MODEL:
+  TYPE: generalized_rcnn
+  CONV_BODY: FPN.add_fpn_ResNet101_conv5_body
+  NUM_CLASSES: 81
+  FASTER_RCNN: True
+  MASK_ON: True
+NUM_GPUS: 8
+SOLVER:
+  WEIGHT_DECAY: 0.0001
+  LR_POLICY: steps_with_decay
+  BASE_LR: 0.02
+  GAMMA: 0.1
+  MAX_ITER: 180000
+  STEPS: [0, 120000, 160000]
+FPN:
+  FPN_ON: True
+  MULTILEVEL_ROIS: True
+  MULTILEVEL_RPN: True
+  USE_GN: True  # Note: use GN on the FPN-specific layers
+RESNETS:
+  STRIDE_1X1: False  # default True for MSRA; False for C2 or Torch models
+  TRANS_FUNC: bottleneck_gn_transformation  # Note: this is a GN bottleneck transform
+  STEM_FUNC: basic_gn_stem  # Note: this is a GN stem
+  SHORTCUT_FUNC: basic_gn_shortcut  # Note: this is a GN shortcut
+FAST_RCNN:
+  ROI_BOX_HEAD: fast_rcnn_heads.add_roi_Xconv1fc_gn_head  # Note: this is a Conv GN head
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 7
+  ROI_XFORM_SAMPLING_RATIO: 2
+MRCNN:
+  ROI_MASK_HEAD: mask_rcnn_heads.mask_rcnn_fcn_head_v1up4convs_gn  # Note: this is a GN mask head
+  RESOLUTION: 28  # (output mask resolution) default 14
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 14  # default 7
+  ROI_XFORM_SAMPLING_RATIO: 2  # default 0
+  DILATION: 1  # default 2
+  CONV_INIT: MSRAFill  # default GaussianFill
+TRAIN:
+  WEIGHTS: https://s3-us-west-2.amazonaws.com/detectron/ImageNetPretrained/47592356/R-101-GN.pkl  # Note: a GN pre-trained model
+  DATASETS: ('coco_2014_train', 'coco_2014_valminusminival')
+  SCALES: (800,)
+  MAX_SIZE: 1333
+  BATCH_SIZE_PER_IM: 512
+  RPN_PRE_NMS_TOP_N: 2000  # Per FPN level
+TEST:
+  DATASETS: ('coco_2014_minival',)
+  SCALE: 800
+  MAX_SIZE: 1333
+  NMS: 0.5
+  RPN_PRE_NMS_TOP_N: 1000  # Per FPN level
+  RPN_POST_NMS_TOP_N: 1000
+OUTPUT_DIR: .

configs/04_2018_gn_baselines/e2e_mask_rcnn_R-101-FPN_3x_gn.yaml

+MODEL:
+  TYPE: generalized_rcnn
+  CONV_BODY: FPN.add_fpn_ResNet101_conv5_body
+  NUM_CLASSES: 81
+  FASTER_RCNN: True
+  MASK_ON: True
+NUM_GPUS: 8
+SOLVER:
+  WEIGHT_DECAY: 0.0001
+  LR_POLICY: steps_with_decay
+  BASE_LR: 0.02
+  GAMMA: 0.1
+  MAX_ITER: 270000
+  STEPS: [0, 210000, 250000]
+FPN:
+  FPN_ON: True
+  MULTILEVEL_ROIS: True
+  MULTILEVEL_RPN: True
+  USE_GN: True  # Note: use GN on the FPN-specific layers
+RESNETS:
+  STRIDE_1X1: False  # default True for MSRA; False for C2 or Torch models
+  TRANS_FUNC: bottleneck_gn_transformation  # Note: this is a GN bottleneck transform
+  STEM_FUNC: basic_gn_stem  # Note: this is a GN stem
+  SHORTCUT_FUNC: basic_gn_shortcut  # Note: this is a GN shortcut
+FAST_RCNN:
+  ROI_BOX_HEAD: fast_rcnn_heads.add_roi_Xconv1fc_gn_head  # Note: this is a Conv GN head
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 7
+  ROI_XFORM_SAMPLING_RATIO: 2
+MRCNN:
+  ROI_MASK_HEAD: mask_rcnn_heads.mask_rcnn_fcn_head_v1up4convs_gn  # Note: this is a GN mask head
+  RESOLUTION: 28  # (output mask resolution) default 14
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 14  # default 7
+  ROI_XFORM_SAMPLING_RATIO: 2  # default 0
+  DILATION: 1  # default 2
+  CONV_INIT: MSRAFill  # default GaussianFill
+TRAIN:
+  WEIGHTS: https://s3-us-west-2.amazonaws.com/detectron/ImageNetPretrained/47592356/R-101-GN.pkl  # Note: a GN pre-trained model
+  DATASETS: ('coco_2014_train', 'coco_2014_valminusminival')
+  SCALES: (800,)
+  MAX_SIZE: 1333
+  BATCH_SIZE_PER_IM: 512
+  RPN_PRE_NMS_TOP_N: 2000  # Per FPN level
+TEST:
+  DATASETS: ('coco_2014_minival',)
+  SCALE: 800
+  MAX_SIZE: 1333
+  NMS: 0.5
+  RPN_PRE_NMS_TOP_N: 1000  # Per FPN level
+  RPN_POST_NMS_TOP_N: 1000
+OUTPUT_DIR: .

configs/04_2018_gn_baselines/e2e_mask_rcnn_R-50-FPN_2x_gn.yaml

+MODEL:
+  TYPE: generalized_rcnn
+  CONV_BODY: FPN.add_fpn_ResNet50_conv5_body
+  NUM_CLASSES: 81
+  FASTER_RCNN: True
+  MASK_ON: True
+NUM_GPUS: 8
+SOLVER:
+  WEIGHT_DECAY: 0.0001
+  LR_POLICY: steps_with_decay
+  BASE_LR: 0.02
+  GAMMA: 0.1
+  MAX_ITER: 180000
+  STEPS: [0, 120000, 160000]
+FPN:
+  FPN_ON: True
+  MULTILEVEL_ROIS: True
+  MULTILEVEL_RPN: True
+  USE_GN: True  # Note: use GN on the FPN-specific layers
+RESNETS:
+  STRIDE_1X1: False  # default True for MSRA; False for C2 or Torch models
+  TRANS_FUNC: bottleneck_gn_transformation  # Note: this is a GN bottleneck transform
+  STEM_FUNC: basic_gn_stem  # Note: this is a GN stem
+  SHORTCUT_FUNC: basic_gn_shortcut  # Note: this is a GN shortcut
+FAST_RCNN:
+  ROI_BOX_HEAD: fast_rcnn_heads.add_roi_Xconv1fc_gn_head  # Note: this is a Conv GN head
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 7
+  ROI_XFORM_SAMPLING_RATIO: 2
+MRCNN:
+  ROI_MASK_HEAD: mask_rcnn_heads.mask_rcnn_fcn_head_v1up4convs_gn  # Note: this is a GN mask head
+  RESOLUTION: 28  # (output mask resolution) default 14
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 14  # default 7
+  ROI_XFORM_SAMPLING_RATIO: 2  # default 0
+  DILATION: 1  # default 2
+  CONV_INIT: MSRAFill  # default GaussianFill
+TRAIN:
+  WEIGHTS: https://s3-us-west-2.amazonaws.com/detectron/ImageNetPretrained/47261647/R-50-GN.pkl  # Note: a GN pre-trained model
+  DATASETS: ('coco_2014_train', 'coco_2014_valminusminival')
+  SCALES: (800,)
+  MAX_SIZE: 1333
+  BATCH_SIZE_PER_IM: 512
+  RPN_PRE_NMS_TOP_N: 2000  # Per FPN level
+TEST:
+  DATASETS: ('coco_2014_minival',)
+  SCALE: 800
+  MAX_SIZE: 1333
+  NMS: 0.5
+  RPN_PRE_NMS_TOP_N: 1000  # Per FPN level
+  RPN_POST_NMS_TOP_N: 1000
+OUTPUT_DIR: .

configs/04_2018_gn_baselines/e2e_mask_rcnn_R-50-FPN_3x_gn.yaml

+MODEL:
+  TYPE: generalized_rcnn
+  CONV_BODY: FPN.add_fpn_ResNet50_conv5_body
+  NUM_CLASSES: 81
+  FASTER_RCNN: True
+  MASK_ON: True
+NUM_GPUS: 8
+SOLVER:
+  WEIGHT_DECAY: 0.0001
+  LR_POLICY: steps_with_decay
+  BASE_LR: 0.02
+  GAMMA: 0.1
+  MAX_ITER: 270000
+  STEPS: [0, 210000, 250000]
+FPN:
+  FPN_ON: True
+  MULTILEVEL_ROIS: True
+  MULTILEVEL_RPN: True
+  USE_GN: True  # Note: use GN on the FPN-specific layers
+RESNETS:
+  STRIDE_1X1: False  # default True for MSRA; False for C2 or Torch models
+  TRANS_FUNC: bottleneck_gn_transformation  # Note: this is a GN bottleneck transform
+  STEM_FUNC: basic_gn_stem  # Note: this is a GN stem
+  SHORTCUT_FUNC: basic_gn_shortcut  # Note: this is a GN shortcut
+FAST_RCNN:
+  ROI_BOX_HEAD: fast_rcnn_heads.add_roi_Xconv1fc_gn_head  # Note: this is a Conv GN head
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 7
+  ROI_XFORM_SAMPLING_RATIO: 2
+MRCNN:
+  ROI_MASK_HEAD: mask_rcnn_heads.mask_rcnn_fcn_head_v1up4convs_gn  # Note: this is a GN mask head
+  RESOLUTION: 28  # (output mask resolution) default 14
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 14  # default 7
+  ROI_XFORM_SAMPLING_RATIO: 2  # default 0
+  DILATION: 1  # default 2
+  CONV_INIT: MSRAFill  # default GaussianFill
+TRAIN:
+  WEIGHTS: https://s3-us-west-2.amazonaws.com/detectron/ImageNetPretrained/47261647/R-50-GN.pkl  # Note: a GN pre-trained model
+  DATASETS: ('coco_2014_train', 'coco_2014_valminusminival')
+  SCALES: (800,)
+  MAX_SIZE: 1333
+  BATCH_SIZE_PER_IM: 512
+  RPN_PRE_NMS_TOP_N: 2000  # Per FPN level
+TEST:
+  DATASETS: ('coco_2014_minival',)
+  SCALE: 800
+  MAX_SIZE: 1333
+  NMS: 0.5
+  RPN_PRE_NMS_TOP_N: 1000  # Per FPN level
+  RPN_POST_NMS_TOP_N: 1000
+OUTPUT_DIR: .

configs/04_2018_gn_baselines/mask_rcnn_R-50-FPN_1x_gn.yaml

+# WARNING: this script uses **pre-computed** BN-based proposals, and is for quick debugging only.
+MODEL:
+  TYPE: generalized_rcnn
+  CONV_BODY: FPN.add_fpn_ResNet50_conv5_body
+  NUM_CLASSES: 81
+  MASK_ON: True
+NUM_GPUS: 8
+SOLVER:
+  WEIGHT_DECAY: 0.0001
+  LR_POLICY: steps_with_decay
+  BASE_LR: 0.02
+  GAMMA: 0.1
+  MAX_ITER: 90000
+  STEPS: [0, 60000, 80000]
+FPN:
+  FPN_ON: True
+  MULTILEVEL_ROIS: True
+  MULTILEVEL_RPN: True
+  USE_GN: True  # Note: use GN on the FPN-specific layers
+RESNETS:
+  STRIDE_1X1: False  # default True for MSRA; False for C2 or Torch models
+  TRANS_FUNC: bottleneck_gn_transformation  # Note: this is a GN bottleneck transform
+  STEM_FUNC: basic_gn_stem  # Note: this is a GN stem
+  SHORTCUT_FUNC: basic_gn_shortcut  # Note: this is a GN shortcut
+FAST_RCNN:
+  ROI_BOX_HEAD: fast_rcnn_heads.add_roi_Xconv1fc_gn_head  # Note: this is a Conv GN head
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 7
+  ROI_XFORM_SAMPLING_RATIO: 2
+MRCNN:
+  ROI_MASK_HEAD: mask_rcnn_heads.mask_rcnn_fcn_head_v1up4convs_gn  # Note: this is a GN mask head
+  RESOLUTION: 28  # (output mask resolution) default 14
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 14  # default 7
+  ROI_XFORM_SAMPLING_RATIO: 2  # default 0
+  DILATION: 1  # default 2
+  CONV_INIT: MSRAFill  # default GaussianFill
+TRAIN:
+  WEIGHTS: https://s3-us-west-2.amazonaws.com/detectron/ImageNetPretrained/47261647/R-50-GN.pkl  # Note: a GN pre-trained model
+  DATASETS: ('coco_2014_train', 'coco_2014_valminusminival')
+  PROPOSAL_FILES: ('https://s3-us-west-2.amazonaws.com/detectron/35998814/12_2017_baselines/rpn_R-50-FPN_1x.yaml.08_06_03.Axg0r179/output/test/coco_2014_train/generalized_rcnn/rpn_proposals.pkl', 'https://s3-us-west-2.amazonaws.com/detectron/35998814/12_2017_baselines/rpn_R-50-FPN_1x.yaml.08_06_03.Axg0r179/output/test/coco_2014_valminusminival/generalized_rcnn/rpn_proposals.pkl')
+  SCALES: (800,)
+  MAX_SIZE: 1333
+  BATCH_SIZE_PER_IM: 512
+TEST:
+  DATASETS: ('coco_2014_minival',)
+  PROPOSAL_FILES: ('https://s3-us-west-2.amazonaws.com/detectron/35998814/12_2017_baselines/rpn_R-50-FPN_1x.yaml.08_06_03.Axg0r179/output/test/coco_2014_minival/generalized_rcnn/rpn_proposals.pkl',)
+  PROPOSAL_LIMIT: 1000
+  SCALE: 800
+  MAX_SIZE: 1333
+  NMS: 0.5
+OUTPUT_DIR: .

configs/04_2018_gn_baselines/scratch_e2e_mask_rcnn_R-101-FPN_3x_gn.yaml

+MODEL:
+  TYPE: generalized_rcnn
+  CONV_BODY: FPN.add_fpn_ResNet101_conv5_body
+  NUM_CLASSES: 81
+  FASTER_RCNN: True
+  MASK_ON: True
+NUM_GPUS: 8
+SOLVER:
+  WEIGHT_DECAY: 0.0001
+  LR_POLICY: steps_with_decay
+  BASE_LR: 0.02
+  GAMMA: 0.1
+  MAX_ITER: 270000
+  STEPS: [0, 210000, 250000]
+FPN:
+  FPN_ON: True
+  MULTILEVEL_ROIS: True
+  MULTILEVEL_RPN: True
+  USE_GN: True  # Note: use GN on the FPN-specific layers
+RESNETS:
+  STRIDE_1X1: False  # default True for MSRA; False for C2 or Torch models
+  TRANS_FUNC: bottleneck_gn_transformation  # Note: this is a GN bottleneck transform
+  STEM_FUNC: basic_gn_stem  # Note: this is a GN stem
+  SHORTCUT_FUNC: basic_gn_shortcut  # Note: this is a GN shortcut
+FAST_RCNN:
+  ROI_BOX_HEAD: fast_rcnn_heads.add_roi_Xconv1fc_gn_head  # Note: this is a Conv GN head
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 7
+  ROI_XFORM_SAMPLING_RATIO: 2
+MRCNN:
+  ROI_MASK_HEAD: mask_rcnn_heads.mask_rcnn_fcn_head_v1up4convs_gn  # Note: this is a GN mask head
+  RESOLUTION: 28  # (output mask resolution) default 14
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 14  # default 7
+  ROI_XFORM_SAMPLING_RATIO: 2  # default 0
+  DILATION: 1  # default 2
+  CONV_INIT: MSRAFill  # default GaussianFill
+TRAIN:
+  # WEIGHTS: N/A
+  DATASETS: ('coco_2014_train', 'coco_2014_valminusminival')
+  SCALES: (800,)
+  MAX_SIZE: 1333
+  BATCH_SIZE_PER_IM: 512
+  RPN_PRE_NMS_TOP_N: 2000  # Per FPN level
+TEST:
+  DATASETS: ('coco_2014_minival',)
+  SCALE: 800
+  MAX_SIZE: 1333
+  NMS: 0.5
+  RPN_PRE_NMS_TOP_N: 1000  # Per FPN level
+  RPN_POST_NMS_TOP_N: 1000
+OUTPUT_DIR: .

configs/04_2018_gn_baselines/scratch_e2e_mask_rcnn_R-50-FPN_3x_gn.yaml

+MODEL:
+  TYPE: generalized_rcnn
+  CONV_BODY: FPN.add_fpn_ResNet50_conv5_body
+  NUM_CLASSES: 81
+  FASTER_RCNN: True
+  MASK_ON: True
+NUM_GPUS: 8
+SOLVER:
+  WEIGHT_DECAY: 0.0001
+  LR_POLICY: steps_with_decay
+  BASE_LR: 0.02
+  GAMMA: 0.1
+  MAX_ITER: 270000
+  STEPS: [0, 210000, 250000]
+FPN:
+  FPN_ON: True
+  MULTILEVEL_ROIS: True
+  MULTILEVEL_RPN: True
+  USE_GN: True  # Note: use GN on the FPN-specific layers
+RESNETS:
+  STRIDE_1X1: False  # default True for MSRA; False for C2 or Torch models
+  TRANS_FUNC: bottleneck_gn_transformation  # Note: this is a GN bottleneck transform
+  STEM_FUNC: basic_gn_stem  # Note: this is a GN stem
+  SHORTCUT_FUNC: basic_gn_shortcut  # Note: this is a GN shortcut
+FAST_RCNN:
+  ROI_BOX_HEAD: fast_rcnn_heads.add_roi_Xconv1fc_gn_head  # Note: this is a Conv GN head
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 7
+  ROI_XFORM_SAMPLING_RATIO: 2
+MRCNN:
+  ROI_MASK_HEAD: mask_rcnn_heads.mask_rcnn_fcn_head_v1up4convs_gn  # Note: this is a GN mask head
+  RESOLUTION: 28  # (output mask resolution) default 14
+  ROI_XFORM_METHOD: RoIAlign
+  ROI_XFORM_RESOLUTION: 14  # default 7
+  ROI_XFORM_SAMPLING_RATIO: 2  # default 0
+  DILATION: 1  # default 2
+  CONV_INIT: MSRAFill  # default GaussianFill
+TRAIN:
+  # WEIGHTS: N/A
+  DATASETS: ('coco_2014_train', 'coco_2014_valminusminival')
+  SCALES: (800,)
+  MAX_SIZE: 1333
+  BATCH_SIZE_PER_IM: 512
+  RPN_PRE_NMS_TOP_N: 2000  # Per FPN level
+TEST:
+  DATASETS: ('coco_2014_minival',)
+  SCALE: 800
+  MAX_SIZE: 1333
+  NMS: 0.5
+  RPN_PRE_NMS_TOP_N: 1000  # Per FPN level
+  RPN_POST_NMS_TOP_N: 1000
+OUTPUT_DIR: .

lib/core/config.py

@@ -592,6 +592,8 @@ __C.SOLVER.MOMENTUM = 0.9
 
 # L2 regularization hyperparameter
 __C.SOLVER.WEIGHT_DECAY = 0.0005
+# L2 regularization hyperparameter for GroupNorm's parameters
+__C.SOLVER.WEIGHT_DECAY_GN = 0.0
 
 # Warm up to SOLVER.BASE_LR over this number of SGD iterations
 __C.SOLVER.WARM_UP_ITERS = 500
@@ -628,6 +630,11 @@ __C.FAST_RCNN.ROI_BOX_HEAD = b''
 # Hidden layer dimension when using an MLP for the RoI box head
 __C.FAST_RCNN.MLP_HEAD_DIM = 1024
 
+# Hidden Conv layer dimension when using Convs for the RoI box head
+__C.FAST_RCNN.CONV_HEAD_DIM = 256
+# Number of stacked Conv layers in the RoI box head
+__C.FAST_RCNN.NUM_STACKED_CONVS = 4
+
 # RoI transformation function (e.g., RoIPool or RoIAlign)
 # (RoIPoolF is the same as RoIPool; ignore the trailing 'F')
 __C.FAST_RCNN.ROI_XFORM_METHOD = b'RoIPoolF'
@@ -708,6 +715,8 @@ __C.FPN.RPN_ASPECT_RATIOS = (0.5, 1, 2)
 __C.FPN.RPN_ANCHOR_START_SIZE = 32
 # Use extra FPN levels, as done in the RetinaNet paper
 __C.FPN.EXTRA_CONV_LEVELS = False
+# Use GroupNorm in the FPN-specific layers (lateral, etc.)
+__C.FPN.USE_GN = False
 
 
 # ---------------------------------------------------------------------------- #
@@ -863,11 +872,27 @@ __C.RESNETS.STRIDE_1X1 = True
 
 # Residual transformation function
 __C.RESNETS.TRANS_FUNC = b'bottleneck_transformation'
+# ResNet's stem function (conv1 and pool1)
+__C.RESNETS.STEM_FUNC = b'basic_bn_stem'
+# ResNet's shortcut function
+__C.RESNETS.SHORTCUT_FUNC = b'basic_bn_shortcut'
 
 # Apply dilation in stage "res5"
 __C.RESNETS.RES5_DILATION = 1
 
 
+# ---------------------------------------------------------------------------- #
+# GroupNorm options
+# ---------------------------------------------------------------------------- #
+__C.GROUP_NORM = AttrDict()
+# Number of dimensions per group in GroupNorm (-1 if using NUM_GROUPS)
+__C.GROUP_NORM.DIM_PER_GP = -1
+# Number of groups in GroupNorm (-1 if using DIM_PER_GP)
+__C.GROUP_NORM.NUM_GROUPS = 32
+# GroupNorm's small constant in the denominator
+__C.GROUP_NORM.EPSILON = 1e-5
+
+
 # ---------------------------------------------------------------------------- #
 # Misc options
 # ---------------------------------------------------------------------------- #

lib/modeling/FPN.py

@@ -27,6 +27,7 @@ from core.config import cfg
 from modeling.generate_anchors import generate_anchors
 from utils.c2 import const_fill
 from utils.c2 import gauss_fill
+from utils.net import get_group_gn
 import modeling.ResNet as ResNet
 import utils.blob as blob_utils
 import utils.boxes as box_utils
@@ -138,7 +139,23 @@ def add_fpn(model, fpn_level_info):
     fpn_dim_lateral = fpn_level_info.dims
     xavier_fill = ('XavierFill', {})
 
-    # For the coarest backbone level: 1x1 conv only seeds recursion
+    # For the coarsest backbone level: 1x1 conv only seeds recursion
+    if cfg.FPN.USE_GN:
+        # use GroupNorm
+        c = model.ConvGN(
+            lateral_input_blobs[0],
+            output_blobs[0],  # note: this is a prefix
+            dim_in=fpn_dim_lateral[0],
+            dim_out=fpn_dim,
+            group_gn=get_group_gn(fpn_dim),
+            kernel=1,
+            pad=0,
+            stride=1,
+            weight_init=xavier_fill,
+            bias_init=const_fill(0.0)
+        )
+        output_blobs[0] = c  # rename it
+    else:
         model.Conv(
             lateral_input_blobs[0],
             output_blobs[0],
@@ -170,6 +187,21 @@ def add_fpn(model, fpn_level_info):
     blobs_fpn = []
     spatial_scales = []
     for i in range(num_backbone_stages):
+        if cfg.FPN.USE_GN:
+            # use GroupNorm
+            fpn_blob = model.ConvGN(
+                output_blobs[i],
+                'fpn_{}'.format(fpn_level_info.blobs[i]),
+                dim_in=fpn_dim,
+                dim_out=fpn_dim,
+                group_gn=get_group_gn(fpn_dim),
+                kernel=3,
+                pad=1,
+                stride=1,
+                weight_init=xavier_fill,
+                bias_init=const_fill(0.0)
+            )
+        else:
             fpn_blob = model.Conv(
                 output_blobs[i],
                 'fpn_{}'.format(fpn_level_info.blobs[i]),
@@ -229,17 +261,34 @@ def add_topdown_lateral_module(
 ):
     """Add a top-down lateral module."""
     # Lateral 1x1 conv
-    lat = model.Conv(
+    if cfg.FPN.USE_GN:
+        # use GroupNorm
+        lat = model.ConvGN(
             fpn_lateral,
             fpn_bottom + '_lateral',
             dim_in=dim_lateral,
             dim_out=dim_top,
+            group_gn=get_group_gn(dim_top),
             kernel=1,
             pad=0,
             stride=1,
             weight_init=(
                 const_fill(0.0) if cfg.FPN.ZERO_INIT_LATERAL
-            else ('XavierFill', {})
+                else ('XavierFill', {})),
+            bias_init=const_fill(0.0)
+        )
+    else:
+        lat = model.Conv(
+            fpn_lateral,
+            fpn_bottom + '_lateral',
+            dim_in=dim_lateral,
+            dim_out=dim_top,
+            kernel=1,
+            pad=0,
+            stride=1,
+            weight_init=(
+                const_fill(0.0)
+                if cfg.FPN.ZERO_INIT_LATERAL else ('XavierFill', {})
             ),
             bias_init=const_fill(0.0)
         )

lib/modeling/ResNet.py

@@ -24,6 +24,7 @@ from __future__ import print_function
 from __future__ import unicode_literals
 
 from core.config import cfg
+from utils.net import get_group_gn
 
 # ---------------------------------------------------------------------------- #
 # Bits for specific architectures (ResNet50, ResNet101, ...)
@@ -91,11 +92,10 @@ def add_ResNet_convX_body(model, block_counts, freeze_at=2):
     The final res5/conv5 stage may be optionally excluded (hence convX, where
     X = 4 or 5)."""
     assert freeze_at in [0, 2, 3, 4, 5]
-    p = model.Conv('data', 'conv1', 3, 64, 7, pad=3, stride=2, no_bias=1)
-    p = model.AffineChannel(p, 'res_conv1_bn', dim=64, inplace=True)
-    p = model.Relu(p, p)
-    p = model.MaxPool(p, 'pool1', kernel=3, pad=1, stride=2)
-    dim_in = 64
+
+    # add the stem (by default, conv1 and pool1 with bn; can support gn)
+    p, dim_in = globals()[cfg.RESNETS.STEM_FUNC](model, 'data')
+
     dim_bottleneck = cfg.RESNETS.NUM_GROUPS * cfg.RESNETS.WIDTH_PER_GROUP
     (n1, n2, n3) = block_counts[:3]
     s, dim_in = add_stage(model, 'res2', p, n1, dim_in, 256, dim_bottleneck, 1)
@@ -182,6 +182,8 @@ def add_residual_block(
     )
 
     # sum -> ReLU
+    # shortcut function: by default using bn; support gn
+    add_shortcut = globals()[cfg.RESNETS.SHORTCUT_FUNC]
     sc = add_shortcut(model, prefix, blob_in, dim_in, dim_out, stride)
     if inplace_sum:
         s = model.net.Sum([tr, sc], tr)
@@ -191,7 +193,16 @@ def add_residual_block(
     return model.Relu(s, s)
 
 
-def add_shortcut(model, prefix, blob_in, dim_in, dim_out, stride):
+# ------------------------------------------------------------------------------
+# various shortcuts (may expand and may consider a new helper)
+# ------------------------------------------------------------------------------
+
+
+def basic_bn_shortcut(model, prefix, blob_in, dim_in, dim_out, stride):
+    """ For a pre-trained network that used BN. An AffineChannel op replaces BN
+    during fine-tuning.
+    """
+
     if dim_in == dim_out:
         return blob_in
 
@@ -207,6 +218,54 @@ def add_shortcut(model, prefix, blob_in, dim_in, dim_out, stride):
     return model.AffineChannel(c, prefix + '_branch1_bn', dim=dim_out)
 
 
+def basic_gn_shortcut(model, prefix, blob_in, dim_in, dim_out, stride):
+    if dim_in == dim_out:
+        return blob_in
+
+    # output name is prefix + '_branch1_gn'
+    return model.ConvGN(
+        blob_in,
+        prefix + '_branch1',
+        dim_in,
+        dim_out,
+        kernel=1,
+        group_gn=get_group_gn(dim_out),
+        stride=stride,
+        pad=0,
+        group=1,
+    )
+
+
+# ------------------------------------------------------------------------------
+# various stems (may expand and may consider a new helper)
+# ------------------------------------------------------------------------------
+
+
+def basic_bn_stem(model, data, **kwargs):
+    """Add a basic ResNet stem. For a pre-trained network that used BN.
+    An AffineChannel op replaces BN during fine-tuning.
+    """
+
+    dim = 64
+    p = model.Conv(data, 'conv1', 3, dim, 7, pad=3, stride=2, no_bias=1)
+    p = model.AffineChannel(p, 'res_conv1_bn', dim=dim, inplace=True)
+    p = model.Relu(p, p)
+    p = model.MaxPool(p, 'pool1', kernel=3, pad=1, stride=2)
+    return p, dim
+
+
+def basic_gn_stem(model, data, **kwargs):
+    """Add a basic ResNet stem (using GN)"""
+
+    dim = 64
+    p = model.ConvGN(
+        data, 'conv1', 3, dim, 7, group_gn=get_group_gn(dim), pad=3, stride=2
+    )
+    p = model.Relu(p, p)
+    p = model.MaxPool(p, 'pool1', kernel=3, pad=1, stride=2)
+    return p, dim
+
+
 # ------------------------------------------------------------------------------
 # various transformations (may expand and may consider a new helper)
 # ------------------------------------------------------------------------------
@@ -270,3 +329,61 @@ def bottleneck_transformation(
         inplace=False
     )
     return cur
+
+
+def bottleneck_gn_transformation(
+    model,
+    blob_in,
+    dim_in,
+    dim_out,
+    stride,
+    prefix,
+    dim_inner,
+    dilation=1,
+    group=1
+):
+    """Add a bottleneck transformation with GroupNorm to the model."""
+    # In original resnet, stride=2 is on 1x1.
+    # In fb.torch resnet, stride=2 is on 3x3.
+    (str1x1, str3x3) = (stride, 1) if cfg.RESNETS.STRIDE_1X1 else (1, stride)
+
+    # conv 1x1 -> GN -> ReLU
+    cur = model.ConvGN(
+        blob_in,
+        prefix + '_branch2a',
+        dim_in,
+        dim_inner,
+        kernel=1,
+        group_gn=get_group_gn(dim_inner),
+        stride=str1x1,
+        pad=0,
+    )
+    cur = model.Relu(cur, cur)
+
+    # conv 3x3 -> GN -> ReLU
+    cur = model.ConvGN(
+        cur,
+        prefix + '_branch2b',
+        dim_inner,
+        dim_inner,
+        kernel=3,
+        group_gn=get_group_gn(dim_inner),
+        stride=str3x3,
+        pad=1 * dilation,
+        dilation=dilation,
+        group=group,
+    )
+    cur = model.Relu(cur, cur)
+
+    # conv 1x1 -> GN (no ReLU)
+    cur = model.ConvGN(
+        cur,
+        prefix + '_branch2c',
+        dim_inner,
+        dim_out,
+        kernel=1,
+        group_gn=get_group_gn(dim_out),
+        stride=1,
+        pad=0,
+    )
+    return cur

lib/modeling/detector.py

@@ -63,6 +63,7 @@ class DetectionModelHelper(cnn.CNNModelHelper):
         self.net.Proto().type = cfg.MODEL.EXECUTION_TYPE
         self.net.Proto().num_workers = cfg.NUM_GPUS * 4
         self.prev_use_cudnn = self.use_cudnn
+        self.gn_params = []  # Param on this list are GroupNorm parameters
 
     def TrainableParams(self, gpu_id=-1):
         """Get the blob names for all trainable parameters, possibly filtered by
@@ -410,6 +411,48 @@ class DetectionModelHelper(cnn.CNNModelHelper):
         )
         return blob_out
 
+    def ConvGN(  # args in the same order of Conv()
+        self, blob_in, prefix, dim_in, dim_out, kernel, stride, pad,
+        group_gn,  # num of groups in gn
+        group=1, dilation=1,
+        weight_init=None,
+        bias_init=None,
+        suffix='_gn',
+        no_conv_bias=1,
+    ):
+        """ConvGN adds a Conv op followed by a GroupNorm op,
+        including learnable scale/bias (gamma/beta)
+        """
+        conv_blob = self.Conv(
+            blob_in,
+            prefix,
+            dim_in,
+            dim_out,
+            kernel,
+            stride=stride,
+            pad=pad,
+            group=group,
+            dilation=dilation,
+            weight_init=weight_init,
+            bias_init=bias_init,
+            no_bias=no_conv_bias)
+
+        if group_gn < 1:
+            logger.warning(
+                'Layer: {} (dim {}): '
+                'group_gn < 1; reset to 1.'.format(prefix, dim_in)
+            )
+            group_gn = 1
+
+        blob_out = self.SpatialGN(
+            conv_blob, prefix + suffix,
+            dim_out, num_groups=group_gn,
+            epsilon=cfg.GROUP_NORM.EPSILON,)
+
+        self.gn_params.append(self.params[-1])  # add gn's bias to list
+        self.gn_params.append(self.params[-2])  # add gn's scale to list
+        return blob_out
+
     def DisableCudnn(self):
         self.prev_use_cudnn = self.use_cudnn
         self.use_cudnn = False

lib/modeling/fast_rcnn_heads.py

@@ -35,6 +35,7 @@ from __future__ import unicode_literals
 from core.config import cfg
 from utils.c2 import const_fill
 from utils.c2 import gauss_fill
+from utils.net import get_group_gn
 import utils.blob as blob_utils
 
 
@@ -109,3 +110,64 @@ def add_roi_2mlp_head(model, blob_in, dim_in, spatial_scale):
     model.FC('fc6', 'fc7', hidden_dim, hidden_dim)
     model.Relu('fc7', 'fc7')
     return 'fc7', hidden_dim
+
+
+def add_roi_Xconv1fc_head(model, blob_in, dim_in, spatial_scale):
+    """Add a X conv + 1fc head, as a reference if not using GroupNorm"""
+    hidden_dim = cfg.FAST_RCNN.CONV_HEAD_DIM
+    roi_size = cfg.FAST_RCNN.ROI_XFORM_RESOLUTION
+    roi_feat = model.RoIFeatureTransform(
+        blob_in,
+        'roi_feat',
+        blob_rois='rois',
+        method=cfg.FAST_RCNN.ROI_XFORM_METHOD,
+        resolution=roi_size,
+        sampling_ratio=cfg.FAST_RCNN.ROI_XFORM_SAMPLING_RATIO,
+        spatial_scale=spatial_scale
+    )
+
+    current = roi_feat
+    for i in range(cfg.FAST_RCNN.NUM_STACKED_CONVS):
+        current = model.Conv(
+            current, 'head_conv' + str(i + 1), dim_in, hidden_dim, 3,
+            stride=1, pad=1,
+            weight_init=('MSRAFill', {}),
+            bias_init=('ConstantFill', {'value': 0.}),
+            no_bias=0)
+        current = model.Relu(current, current)
+        dim_in = hidden_dim
+
+    fc_dim = cfg.FAST_RCNN.MLP_HEAD_DIM
+    model.FC(current, 'fc6', dim_in * roi_size * roi_size, fc_dim)
+    model.Relu('fc6', 'fc6')
+    return 'fc6', fc_dim
+
+
+def add_roi_Xconv1fc_gn_head(model, blob_in, dim_in, spatial_scale):
+    """Add a X conv + 1fc head, with GroupNorm"""
+    hidden_dim = cfg.FAST_RCNN.CONV_HEAD_DIM
+    roi_size = cfg.FAST_RCNN.ROI_XFORM_RESOLUTION
+    roi_feat = model.RoIFeatureTransform(
+        blob_in, 'roi_feat',
+        blob_rois='rois',
+        method=cfg.FAST_RCNN.ROI_XFORM_METHOD,
+        resolution=roi_size,
+        sampling_ratio=cfg.FAST_RCNN.ROI_XFORM_SAMPLING_RATIO,
+        spatial_scale=spatial_scale
+    )
+
+    current = roi_feat
+    for i in range(cfg.FAST_RCNN.NUM_STACKED_CONVS):
+        current = model.ConvGN(
+            current, 'head_conv' + str(i + 1), dim_in, hidden_dim, 3,
+            group_gn=get_group_gn(hidden_dim),
+            stride=1, pad=1,
+            weight_init=('MSRAFill', {}),
+            bias_init=('ConstantFill', {'value': 0.}))
+        current = model.Relu(current, current)
+        dim_in = hidden_dim
+
+    fc_dim = cfg.FAST_RCNN.MLP_HEAD_DIM
+    model.FC(current, 'fc6', dim_in * roi_size * roi_size, fc_dim)
+    model.Relu('fc6', 'fc6')
+    return 'fc6', fc_dim

lib/modeling/mask_rcnn_heads.py

@@ -35,6 +35,7 @@ from __future__ import unicode_literals
 from core.config import cfg
 from utils.c2 import const_fill
 from utils.c2 import gauss_fill
+from utils.net import get_group_gn
 import modeling.ResNet as ResNet
 import utils.blob as blob_utils
 
@@ -114,6 +115,13 @@ def mask_rcnn_fcn_head_v1up4convs(model, blob_in, dim_in, spatial_scale):
     )
 
 
+def mask_rcnn_fcn_head_v1up4convs_gn(model, blob_in, dim_in, spatial_scale):
+    """v1up design: 4 * (conv 3x3), convT 2x2, with GroupNorm"""
+    return mask_rcnn_fcn_head_v1upXconvs_gn(
+        model, blob_in, dim_in, spatial_scale, 4
+    )
+
+
 def mask_rcnn_fcn_head_v1up(model, blob_in, dim_in, spatial_scale):
     """v1up design: 2 * (conv 3x3), convT 2x2."""
     return mask_rcnn_fcn_head_v1upXconvs(
@@ -170,6 +178,56 @@ def mask_rcnn_fcn_head_v1upXconvs(
     return blob_mask, dim_inner
 
 
+def mask_rcnn_fcn_head_v1upXconvs_gn(
+    model, blob_in, dim_in, spatial_scale, num_convs
+):
+    """v1upXconvs design: X * (conv 3x3), convT 2x2, with GroupNorm"""
+    current = model.RoIFeatureTransform(
+        blob_in,
+        blob_out='_mask_roi_feat',
+        blob_rois='mask_rois',
+        method=cfg.MRCNN.ROI_XFORM_METHOD,
+        resolution=cfg.MRCNN.ROI_XFORM_RESOLUTION,
+        sampling_ratio=cfg.MRCNN.ROI_XFORM_SAMPLING_RATIO,
+        spatial_scale=spatial_scale
+    )
+
+    dilation = cfg.MRCNN.DILATION
+    dim_inner = cfg.MRCNN.DIM_REDUCED
+
+    for i in range(num_convs):
+        current = model.ConvGN(
+            current,
+            '_mask_fcn' + str(i + 1),
+            dim_in,
+            dim_inner,
+            group_gn=get_group_gn(dim_inner),
+            kernel=3,
+            pad=1 * dilation,
+            stride=1,
+            weight_init=(cfg.MRCNN.CONV_INIT, {'std': 0.001}),
+            bias_init=('ConstantFill', {'value': 0.})
+        )
+        current = model.Relu(current, current)
+        dim_in = dim_inner
+
+    # upsample layer
+    model.ConvTranspose(
+        current,
+        'conv5_mask',
+        dim_inner,
+        dim_inner,
+        kernel=2,
+        pad=0,
+        stride=2,
+        weight_init=(cfg.MRCNN.CONV_INIT, {'std': 0.001}),
+        bias_init=const_fill(0.0)
+    )
+    blob_mask = model.Relu('conv5_mask', 'conv5_mask')
+
+    return blob_mask, dim_inner
+
+
 def mask_rcnn_fcn_head_v0upshare(model, blob_in, dim_in, spatial_scale):
     """Use a ResNet "conv5" / "stage5" head for mask prediction. Weights and
     computation are shared with the conv5 box head. Computation can only be

lib/modeling/optimizer.py

@@ -99,6 +99,10 @@ def add_single_gpu_param_update_ops(model, gpu_id):
     wd = model.param_init_net.ConstantFill(
         [], 'wd', shape=[1], value=cfg.SOLVER.WEIGHT_DECAY
     )
+    # weight decay of GroupNorm's parameters
+    wd_gn = model.param_init_net.ConstantFill(
+        [], 'wd_gn', shape=[1], value=cfg.SOLVER.WEIGHT_DECAY_GN
+    )
     for param in model.TrainableParams(gpu_id=gpu_id):
         logger.debug('param ' + str(param) + ' will be updated')
         param_grad = model.param_to_grad[param]
@@ -112,6 +116,9 @@ def add_single_gpu_param_update_ops(model, gpu_id):
             # (1) Do not apply weight decay
             # (2) Use a 2x higher learning rate
             model.Scale(param_grad, param_grad, scale=2.0)
+        elif param in model.gn_params:
+            # Special treatment for GroupNorm's parameters
+            model.WeightedSum([param_grad, one, param, wd_gn], param_grad)
         elif cfg.SOLVER.WEIGHT_DECAY > 0:
             # Apply weight decay to non-bias weights
             model.WeightedSum([param_grad, one, param, wd], param_grad)

lib/utils/net.py

@@ -274,3 +274,22 @@ def configure_bbox_reg_weights(model, saved_cfg):
             'longer be used for training. To upgrade it to a trainable model '
             'please use fb/compat/convert_bbox_reg_normalized_model.py.'
         )
+
+
+def get_group_gn(dim):
+    """
+    get number of groups used by GroupNorm, based on number of channels
+    """
+    dim_per_gp = cfg.GROUP_NORM.DIM_PER_GP
+    num_groups = cfg.GROUP_NORM.NUM_GROUPS
+
+    assert dim_per_gp == -1 or num_groups == -1, \
+        "GroupNorm: can only specify G or C/G."
+
+    if dim_per_gp > 0:
+        assert dim % dim_per_gp == 0
+        group_gn = dim // dim_per_gp
+    else:
+        assert dim % num_groups == 0
+        group_gn = num_groups
+    return group_gn