support no label training (#2576)

* support no label training

* fix load_crowd

* update to fit rbox

* add empty_ratio

* update configs

* support mask rcnn

* clean drop_empty for mot & keypoint

* refine is_crowd

configs/cascade_rcnn/_base_/cascade_fpn_reader.yml

@@ -25,7 +25,6 @@ EvalReader:
   batch_size: 1
   shuffle: false
   drop_last: false
-  drop_empty: false
 
 
 TestReader:

configs/cascade_rcnn/_base_/cascade_mask_fpn_reader.yml

@@ -25,7 +25,6 @@ EvalReader:
   batch_size: 1
   shuffle: false
   drop_last: false
-  drop_empty: false
 
 
 TestReader:

configs/dota/_base_/s2anet_reader.yml

@@ -26,7 +26,6 @@ EvalReader:
   batch_size: 1
   shuffle: false
   drop_last: false
-  drop_empty: false
 
 
 TestReader:

configs/face_detection/_base_/face_reader.yml

@@ -34,7 +34,6 @@ EvalReader:
     - NormalizeImage: {mean:  [123, 117, 104], std: [127.502231, 127.502231, 127.502231], is_scale: false}
     - Permute: {}
   batch_size: 1
-  drop_empty: false
 
 
 TestReader:

configs/faster_rcnn/_base_/faster_fpn_reader.yml

@@ -25,7 +25,6 @@ EvalReader:
   batch_size: 1
   shuffle: false
   drop_last: false
-  drop_empty: false
 
 
 TestReader:

configs/faster_rcnn/_base_/faster_reader.yml

@@ -25,7 +25,6 @@ EvalReader:
   batch_size: 1
   shuffle: false
   drop_last: false
-  drop_empty: false
 
 
 TestReader:

configs/keypoint/higherhrnet/higherhrnet_hrnet_w32_512.yml

@@ -119,7 +119,6 @@ EvalReader:
         is_scale: true
     - Permute: {}
   batch_size: 1
-  drop_empty: false
 
 TestReader:
   sample_transforms:

configs/keypoint/higherhrnet/higherhrnet_hrnet_w32_512_swahr.yml

@@ -120,7 +120,6 @@ EvalReader:
         is_scale: true
     - Permute: {}
   batch_size: 1
-  drop_empty: false
 
 TestReader:
   sample_transforms:

configs/keypoint/higherhrnet/higherhrnet_hrnet_w32_640.yml

@@ -119,7 +119,6 @@ EvalReader:
         is_scale: true
     - Permute: {}
   batch_size: 1
-  drop_empty: false
 
 TestReader:
   sample_transforms:

configs/keypoint/hrnet/hrnet_w32_256x192.yml

@@ -128,7 +128,6 @@ EvalReader:
         is_scale: true
     - Permute: {}
   batch_size: 16
-  drop_empty: false
 
 TestReader:
   sample_transforms:

configs/keypoint/hrnet/hrnet_w32_384x288.yml

@@ -129,7 +129,6 @@ EvalReader:
         is_scale: true
     - Permute: {}
   batch_size: 16
-  drop_empty: false
 
 TestReader:
   sample_transforms:

configs/mask_rcnn/_base_/mask_fpn_reader.yml

@@ -25,7 +25,6 @@ EvalReader:
   batch_size: 1
   shuffle: false
   drop_last: false
-  drop_empty: false
 
 
 TestReader:

configs/mask_rcnn/_base_/mask_reader.yml

@@ -26,7 +26,6 @@ EvalReader:
   batch_size: 1
   shuffle: false
   drop_last: false
-  drop_empty: false
 
 
 TestReader:
@@ -40,4 +39,3 @@ TestReader:
   batch_size: 1
   shuffle: false
   drop_last: false
-  drop_empty: false

configs/mot/jde/_base_/jde_reader_1088x608.yml

@@ -45,7 +45,6 @@ EvalReader:
     - BboxCXCYWH2XYXY: {}
     - Norm2PixelBbox: {}
   batch_size: 1
-  drop_empty: false
 
 
 TestReader:

configs/mot/jde/_base_/jde_reader_576x320.yml

@@ -45,7 +45,6 @@ EvalReader:
     - BboxCXCYWH2XYXY: {}
     - Norm2PixelBbox: {}
   batch_size: 1
-  drop_empty: false
 
 
 TestReader:

configs/mot/jde/_base_/jde_reader_864x480.yml

@@ -45,7 +45,6 @@ EvalReader:
     - BboxCXCYWH2XYXY: {}
     - Norm2PixelBbox: {}
   batch_size: 1
-  drop_empty: false
 
 
 TestReader:

configs/ppyolo/_base_/ppyolo_reader.yml

@@ -30,7 +30,6 @@ EvalReader:
     - NormalizeImage: {mean: [0.485, 0.456, 0.406], std: [0.229, 0.224, 0.225], is_scale: True}
     - Permute: {}
   batch_size: 8
-  drop_empty: false
 
 TestReader:
   inputs_def:

configs/ppyolo/_base_/ppyolo_tiny_reader.yml

@@ -30,7 +30,6 @@ EvalReader:
     - NormalizeImage: {mean: [0.485, 0.456, 0.406], std: [0.229, 0.224, 0.225], is_scale: True}
     - Permute: {}
   batch_size: 8
-  drop_empty: false
 
 TestReader:
   inputs_def:

configs/ppyolo/_base_/ppyolov2_reader.yml

@@ -30,7 +30,6 @@ EvalReader:
     - NormalizeImage: {mean: [0.485, 0.456, 0.406], std: [0.229, 0.224, 0.225], is_scale: True}
     - Permute: {}
   batch_size: 8
-  drop_empty: false
 
 TestReader:
   inputs_def:

configs/ppyolo/ppyolo_mbv3_large_coco.yml

@@ -47,7 +47,6 @@ EvalReader:
     - NormalizeImage: {mean: [0.485, 0.456, 0.406], std: [0.229, 0.224, 0.225], is_scale: True}
     - Permute: {}
   batch_size: 8
-  drop_empty: false
 
 TestReader:
   inputs_def:

configs/ppyolo/ppyolo_mbv3_small_coco.yml

@@ -47,7 +47,6 @@ EvalReader:
     - NormalizeImage: {mean: [0.485, 0.456, 0.406], std: [0.229, 0.224, 0.225], is_scale: True}
     - Permute: {}
   batch_size: 8
-  drop_empty: false
 
 TestReader:
   inputs_def:

configs/ppyolo/ppyolo_r18vd_coco.yml

@@ -47,7 +47,6 @@ EvalReader:
     - NormalizeImage: {mean: [0.485, 0.456, 0.406], std: [0.229, 0.224, 0.225], is_scale: True}
     - Permute: {}
   batch_size: 8
-  drop_empty: false
 
 TestReader:
   inputs_def:

configs/rcnn_enhance/_base_/faster_rcnn_enhance_reader.yml

@@ -27,7 +27,6 @@ EvalReader:
   batch_size: 1
   shuffle: false
   drop_last: false
-  drop_empty: false
 
 
 TestReader:

configs/solov2/_base_/solov2_reader.yml

@@ -28,7 +28,6 @@ EvalReader:
   batch_size: 1
   shuffle: false
   drop_last: false
-  drop_empty: false
 
 
 TestReader:

configs/ssd/_base_/ssd_mobilenet_reader.yml

@@ -26,7 +26,6 @@ EvalReader:
     - NormalizeImage: {mean: [127.5, 127.5, 127.5], std: [127.502231, 127.502231, 127.502231], is_scale: false}
     - Permute: {}
   batch_size: 1
-  drop_empty: false
 
 
 TestReader:

configs/ssd/_base_/ssd_reader.yml

@@ -29,7 +29,6 @@ EvalReader:
     - NormalizeImage: {mean: [104., 117., 123.], std: [1., 1., 1.], is_scale: false}
     - Permute: {}
   batch_size: 1
-  drop_empty: false
 
 TestReader:
   inputs_def:

configs/ssd/_base_/ssdlite300_reader.yml

@@ -26,7 +26,6 @@ EvalReader:
     - NormalizeImage: {mean: [0.485, 0.456, 0.406], std: [0.229, 0.224, 0.225], is_scale: true}
     - Permute: {}
   batch_size: 1
-  drop_empty: false
 
 
 TestReader:

configs/ssd/_base_/ssdlite320_reader.yml

@@ -26,7 +26,6 @@ EvalReader:
     - NormalizeImage: {mean: [0.485, 0.456, 0.406], std: [0.229, 0.224, 0.225], is_scale: true}
     - Permute: {}
   batch_size: 1
-  drop_empty: false
 
 
 TestReader:

configs/ttfnet/_base_/pafnet_lite_reader.yml

@@ -27,7 +27,6 @@ EvalReader:
   - Permute: {}
   batch_size: 1
   drop_last: false
-  drop_empty: false
 
 TestReader:
   sample_transforms:
@@ -37,4 +36,3 @@ TestReader:
   - Permute: {}
   batch_size: 1
   drop_last: false
-  drop_empty: false

configs/ttfnet/_base_/pafnet_reader.yml

@@ -27,7 +27,6 @@ EvalReader:
   - Permute: {}
   batch_size: 1
   drop_last: false
-  drop_empty: false
 
 TestReader:
   sample_transforms:
@@ -37,4 +36,3 @@ TestReader:
   - Permute: {}
   batch_size: 1
   drop_last: false
-  drop_empty: false

configs/ttfnet/_base_/ttfnet_reader.yml

@@ -22,7 +22,6 @@ EvalReader:
   - Permute: {}
   batch_size: 1
   drop_last: false
-  drop_empty: false
 
 TestReader:
   sample_transforms:
@@ -32,4 +31,3 @@ TestReader:
   - Permute: {}
   batch_size: 1
   drop_last: false
-  drop_empty: false

configs/yolov3/_base_/yolov3_reader.yml

@@ -32,7 +32,6 @@ EvalReader:
     - NormalizeImage: {mean: [0.485, 0.456, 0.406], std: [0.229, 0.224, 0.225], is_scale: True}
     - Permute: {}
   batch_size: 1
-  drop_empty: false
 
 TestReader:
   inputs_def:

ppdet/data/reader.py

@@ -116,8 +116,6 @@ class BaseDataLoader(object):
         shuffle (bool): whether to shuffle samples
         drop_last (bool): whether to drop the last incomplete,
                           default False
-        drop_empty (bool): whether to drop samples with no ground
-                           truth labels, default True
         num_classes (int): class number of dataset, default 80
         collate_batch (bool): whether to collate batch in dataloader.
             If set to True, the samples will collate into batch according
@@ -140,7 +138,6 @@ class BaseDataLoader(object):
                  batch_size=1,
                  shuffle=False,
                  drop_last=False,
-                 drop_empty=True,
                  num_classes=80,
                  collate_batch=True,
                  use_shared_memory=False,
@@ -231,13 +228,12 @@ class TrainReader(BaseDataLoader):
                  batch_size=1,
                  shuffle=True,
                  drop_last=True,
-                 drop_empty=True,
                  num_classes=80,
                  collate_batch=True,
                  **kwargs):
-        super(TrainReader, self).__init__(
-            sample_transforms, batch_transforms, batch_size, shuffle, drop_last,
-            drop_empty, num_classes, collate_batch, **kwargs)
+        super(TrainReader, self).__init__(sample_transforms, batch_transforms,
+                                          batch_size, shuffle, drop_last,
+                                          num_classes, collate_batch, **kwargs)
 
 
 @register
@@ -250,12 +246,11 @@ class EvalReader(BaseDataLoader):
                  batch_size=1,
                  shuffle=False,
                  drop_last=True,
-                 drop_empty=True,
                  num_classes=80,
                  **kwargs):
         super(EvalReader, self).__init__(sample_transforms, batch_transforms,
                                          batch_size, shuffle, drop_last,
-                                         drop_empty, num_classes, **kwargs)
+                                         num_classes, **kwargs)
 
 
 @register
@@ -268,12 +263,11 @@ class TestReader(BaseDataLoader):
                  batch_size=1,
                  shuffle=False,
                  drop_last=False,
-                 drop_empty=True,
                  num_classes=80,
                  **kwargs):
         super(TestReader, self).__init__(sample_transforms, batch_transforms,
                                          batch_size, shuffle, drop_last,
-                                         drop_empty, num_classes, **kwargs)
+                                         num_classes, **kwargs)
 
 
 @register
@@ -286,12 +280,11 @@ class EvalMOTReader(BaseDataLoader):
                  batch_size=1,
                  shuffle=False,
                  drop_last=False,
-                 drop_empty=True,
                  num_classes=1,
                  **kwargs):
         super(EvalMOTReader, self).__init__(sample_transforms, batch_transforms,
                                             batch_size, shuffle, drop_last,
-                                            drop_empty, num_classes, **kwargs)
+                                            num_classes, **kwargs)
 
 
 @register
@@ -304,9 +297,8 @@ class TestMOTReader(BaseDataLoader):
                  batch_size=1,
                  shuffle=False,
                  drop_last=False,
-                 drop_empty=True,
                  num_classes=1,
                  **kwargs):
         super(TestMOTReader, self).__init__(sample_transforms, batch_transforms,
                                             batch_size, shuffle, drop_last,
-                                            drop_empty, num_classes, **kwargs)
+                                            num_classes, **kwargs)

ppdet/data/source/coco.py

@@ -33,6 +33,12 @@ class COCODataSet(DetDataset):
         anno_path (str): coco annotation file path.
         data_fields (list): key name of data dictionary, at least have 'image'.
         sample_num (int): number of samples to load, -1 means all.
+        load_crowd (bool): whether to load crowded ground-truth. 
+            False as default
+        allow_empty (bool): whether to load empty entry. False as default
+        empty_ratio (float): the ratio of empty record number to total 
+            record's, if empty_ratio is out of [0. ,1.), do not sample the 
+            records. 1. as default
     """
 
     def __init__(self,
@@ -40,11 +46,26 @@ class COCODataSet(DetDataset):
                  image_dir=None,
                  anno_path=None,
                  data_fields=['image'],
-                 sample_num=-1):
+                 sample_num=-1,
+                 load_crowd=False,
+                 allow_empty=False,
+                 empty_ratio=1.):
         super(COCODataSet, self).__init__(dataset_dir, image_dir, anno_path,
                                           data_fields, sample_num)
         self.load_image_only = False
         self.load_semantic = False
+        self.load_crowd = load_crowd
+        self.allow_empty = allow_empty
+        self.empty_ratio = empty_ratio
+
+    def _sample_empty(self, records, num):
+        # if empty_ratio is out of [0. ,1.), do not sample the records
+        if self.empty_ratio < 0. or self.empty_ratio >= 1.:
+            return records
+        import random
+        sample_num = int(num * self.empty_ratio / (1 - self.empty_ratio))
+        records = random.sample(records, sample_num)
+        return records
 
     def parse_dataset(self):
         anno_path = os.path.join(self.dataset_dir, self.anno_path)
@@ -58,6 +79,7 @@ class COCODataSet(DetDataset):
         img_ids.sort()
         cat_ids = coco.getCatIds()
         records = []
+        empty_records = []
         ct = 0
 
         self.catid2clsid = dict({catid: i for i, catid in enumerate(cat_ids)})
@@ -79,6 +101,7 @@ class COCODataSet(DetDataset):
 
             im_path = os.path.join(image_dir,
                                    im_fname) if image_dir else im_fname
+            is_empty = False
             if not os.path.exists(im_path):
                 logger.warning('Illegal image file: {}, and it will be '
                                'ignored'.format(im_path))
@@ -98,12 +121,16 @@ class COCODataSet(DetDataset):
             } if 'image' in self.data_fields else {}
 
             if not self.load_image_only:
-                ins_anno_ids = coco.getAnnIds(imgIds=[img_id], iscrowd=False)
+                ins_anno_ids = coco.getAnnIds(
+                    imgIds=[img_id], iscrowd=None if self.load_crowd else False)
                 instances = coco.loadAnns(ins_anno_ids)
 
                 bboxes = []
+                is_rbox_anno = False
                 for inst in instances:
                     # check gt bbox
+                    if inst.get('ignore', False):
+                        continue
                     if 'bbox' not in inst.keys():
                         continue
                     else:
@@ -137,8 +164,10 @@ class COCODataSet(DetDataset):
                                 img_id, float(inst['area']), x1, y1, x2, y2))
 
                 num_bbox = len(bboxes)
-                if num_bbox <= 0:
+                if num_bbox <= 0 and not self.allow_empty:
                     continue
+                elif num_bbox <= 0:
+                    is_empty = True
 
                 gt_bbox = np.zeros((num_bbox, 4), dtype=np.float32)
                 if is_rbox_anno:
@@ -165,7 +194,8 @@ class COCODataSet(DetDataset):
                         gt_poly[i] = box['segmentation']
                         has_segmentation = True
 
-                if has_segmentation and not any(gt_poly):
+                if has_segmentation and not any(
+                        gt_poly) and not self.allow_empty:
                     continue
 
                 if is_rbox_anno:
@@ -196,10 +226,16 @@ class COCODataSet(DetDataset):
 
             logger.debug('Load file: {}, im_id: {}, h: {}, w: {}.'.format(
                 im_path, img_id, im_h, im_w))
+            if is_empty:
+                empty_records.append(coco_rec)
+            else:
                 records.append(coco_rec)
             ct += 1
             if self.sample_num > 0 and ct >= self.sample_num:
                 break
-        assert len(records) > 0, 'not found any coco record in %s' % (anno_path)
+        assert ct > 0, 'not found any coco record in %s' % (anno_path)
         logger.debug('{} samples in file {}'.format(ct, anno_path))
+        if len(empty_records) > 0:
+            empty_records = self._sample_empty(empty_records, len(records))
+            records += empty_records
         self.roidbs = records

ppdet/modeling/bbox_utils.py

@@ -124,6 +124,10 @@ def bbox_overlaps(boxes1, boxes2):
     Return:
         overlaps (Tensor): overlaps between boxes1 and boxes2 with shape [M, N]
     """
+    M = boxes1.shape[0]
+    N = boxes2.shape[0]
+    if M * N == 0:
+        return paddle.zeros([M, N], dtype='float32')
     area1 = bbox_area(boxes1)
     area2 = bbox_area(boxes2)
 

ppdet/modeling/heads/bbox_head.py

@@ -265,14 +265,26 @@ class BBoxHead(nn.Layer):
         targets (list[List[Tensor]]): bbox targets containing tgt_labels, tgt_bboxes and tgt_gt_inds
         rois (List[Tensor]): RoIs generated in each batch
         """
+        cls_name = 'loss_bbox_cls'
+        reg_name = 'loss_bbox_reg'
+        loss_bbox = {}
+
         # TODO: better pass args
         tgt_labels, tgt_bboxes, tgt_gt_inds = targets
+
+        # bbox cls
         tgt_labels = paddle.concat(tgt_labels) if len(
             tgt_labels) > 1 else tgt_labels[0]
+        valid_inds = paddle.nonzero(tgt_labels >= 0).flatten()
+        if valid_inds.shape[0] == 0:
+            loss_bbox[cls_name] = paddle.zeros([1], dtype='float32')
+        else:
             tgt_labels = tgt_labels.cast('int64')
             tgt_labels.stop_gradient = True
             loss_bbox_cls = F.cross_entropy(
                 input=scores, label=tgt_labels, reduction='mean')
+            loss_bbox[cls_name] = loss_bbox_cls
+
         # bbox reg
 
         cls_agnostic_bbox_reg = deltas.shape[1] == 4
@@ -281,14 +293,9 @@ class BBoxHead(nn.Layer):
             paddle.logical_and(tgt_labels >= 0, tgt_labels <
                                self.num_classes)).flatten()
 
-        cls_name = 'loss_bbox_cls'
-        reg_name = 'loss_bbox_reg'
-        loss_bbox = {}
-
-        loss_weight = 1.
         if fg_inds.numel() == 0:
-            fg_inds = paddle.zeros([1], dtype='int32')
-            loss_weight = 0.
+            loss_bbox[reg_name] = paddle.zeros([1], dtype='float32')
+            return loss_bbox
 
         if cls_agnostic_bbox_reg:
             reg_delta = paddle.gather(deltas, fg_inds)
@@ -323,8 +330,7 @@ class BBoxHead(nn.Layer):
             loss_bbox_reg = paddle.abs(reg_delta - reg_target).sum(
             ) / tgt_labels.shape[0]
 
-        loss_bbox[cls_name] = loss_bbox_cls * loss_weight
-        loss_bbox[reg_name] = loss_bbox_reg * loss_weight
+        loss_bbox[reg_name] = loss_bbox_reg
 
         return loss_bbox
 

ppdet/modeling/proposal_generator/rpn_head.py

@@ -238,6 +238,9 @@ class RPNHead(nn.Layer):
         valid_ind = paddle.nonzero(valid_mask)
 
         # cls loss
+        if valid_ind.shape[0] == 0:
+            loss_rpn_cls = paddle.zeros([1], dtype='float32')
+        else:
             score_pred = paddle.gather(scores, valid_ind)
             score_label = paddle.gather(score_tgt, valid_ind).cast('float32')
             score_label.stop_gradient = True
@@ -245,6 +248,9 @@ class RPNHead(nn.Layer):
                 logit=score_pred, label=score_label, reduction="sum")
 
         # reg loss
+        if pos_ind.shape[0] == 0:
+            loss_rpn_reg = paddle.zeros([1], dtype='float32')
+        else:
             loc_pred = paddle.gather(deltas, pos_ind)
             loc_tgt = paddle.concat(loc_tgt)
             loc_tgt = paddle.gather(loc_tgt, pos_ind)

ppdet/modeling/proposal_generator/target.py

@@ -28,31 +28,38 @@ def rpn_anchor_target(anchors,
                       rpn_fg_fraction,
                       use_random=True,
                       batch_size=1,
+                      ignore_thresh=-1,
+                      is_crowd=None,
                       weights=[1., 1., 1., 1.]):
     tgt_labels = []
     tgt_bboxes = []
-
     tgt_deltas = []
     for i in range(batch_size):
         gt_bbox = gt_boxes[i]
-
+        is_crowd_i = is_crowd[i] if is_crowd else None
         # Step1: match anchor and gt_bbox
         matches, match_labels = label_box(
-            anchors, gt_bbox, rpn_positive_overlap, rpn_negative_overlap, True)
+            anchors, gt_bbox, rpn_positive_overlap, rpn_negative_overlap, True,
+            ignore_thresh, is_crowd_i)
         # Step2: sample anchor 
         fg_inds, bg_inds = subsample_labels(match_labels, rpn_batch_size_per_im,
                                             rpn_fg_fraction, 0, use_random)
         # Fill with the ignore label (-1), then set positive and negative labels
         labels = paddle.full(match_labels.shape, -1, dtype='int32')
-        labels = paddle.scatter(labels, fg_inds, paddle.ones_like(fg_inds))
+        if bg_inds.shape[0] > 0:
             labels = paddle.scatter(labels, bg_inds, paddle.zeros_like(bg_inds))
+        if fg_inds.shape[0] > 0:
+            labels = paddle.scatter(labels, fg_inds, paddle.ones_like(fg_inds))
         # Step3: make output  
+        if gt_bbox.shape[0] == 0:
+            matched_gt_boxes = paddle.zeros([0, 4])
+            tgt_delta = paddle.zeros([0, 4])
+        else:
             matched_gt_boxes = paddle.gather(gt_bbox, matches)
-
             tgt_delta = bbox2delta(anchors, matched_gt_boxes, weights)
-        labels.stop_gradient = True
             matched_gt_boxes.stop_gradient = True
             tgt_delta.stop_gradient = True
+        labels.stop_gradient = True
         tgt_labels.append(labels)
         tgt_bboxes.append(matched_gt_boxes)
         tgt_deltas.append(tgt_delta)
@@ -60,16 +67,46 @@ def rpn_anchor_target(anchors,
     return tgt_labels, tgt_bboxes, tgt_deltas
 
 
-def label_box(anchors, gt_boxes, positive_overlap, negative_overlap,
-              allow_low_quality):
+def label_box(anchors,
+              gt_boxes,
+              positive_overlap,
+              negative_overlap,
+              allow_low_quality,
+              ignore_thresh,
+              is_crowd=None):
     iou = bbox_overlaps(gt_boxes, anchors)
-    if iou.numel() == 0:
+    n_gt = gt_boxes.shape[0]
+    if n_gt == 0 or is_crowd is None:
+        n_gt_crowd = 0
+    else:
+        n_gt_crowd = paddle.nonzero(is_crowd).shape[0]
+    if iou.shape[0] == 0 or n_gt_crowd == n_gt:
+        # No truth, assign everything to background
         default_matches = paddle.full((iou.shape[1], ), 0, dtype='int64')
-        default_match_labels = paddle.full((iou.shape[1], ), -1, dtype='int32')
+        default_match_labels = paddle.full((iou.shape[1], ), 0, dtype='int32')
         return default_matches, default_match_labels
+    # if ignore_thresh > 0, remove anchor if it is closed to 
+    # one of the crowded ground-truth
+    if n_gt_crowd > 0:
+        N_a = anchors.shape[0]
+        ones = paddle.ones([N_a])
+        mask = is_crowd * ones
+
+        if ignore_thresh > 0:
+            crowd_iou = iou * mask
+            valid = (paddle.sum((crowd_iou > ignore_thresh).cast('int32'),
+                                axis=0) > 0).cast('float32')
+            iou = iou * (1 - valid) - valid
+
+        # ignore the iou between anchor and crowded ground-truth
+        iou = iou * (1 - mask) - mask
+
     matched_vals, matches = paddle.topk(iou, k=1, axis=0)
     match_labels = paddle.full(matches.shape, -1, dtype='int32')
-    match_labels = paddle.where(matched_vals < negative_overlap,
+    # set ignored anchor with iou = -1
+    neg_cond = paddle.logical_and(matched_vals > -1,
+                                  matched_vals < negative_overlap)
+    match_labels = paddle.where(neg_cond,
                                 paddle.zeros_like(match_labels), match_labels)
     match_labels = paddle.where(matched_vals >= positive_overlap,
                                 paddle.ones_like(match_labels), match_labels)
@@ -84,6 +121,7 @@ def label_box(anchors, gt_boxes, positive_overlap, negative_overlap,
 
     matches = matches.flatten()
     match_labels = match_labels.flatten()
+
     return matches, match_labels
 
 
@@ -96,24 +134,36 @@ def subsample_labels(labels,
         paddle.logical_and(labels != -1, labels != bg_label))
     negative = paddle.nonzero(labels == bg_label)
 
-    positive = positive.cast('int32').flatten()
-    negative = negative.cast('int32').flatten()
-
     fg_num = int(num_samples * fg_fraction)
     fg_num = min(positive.numel(), fg_num)
     bg_num = num_samples - fg_num
     bg_num = min(negative.numel(), bg_num)
+    if fg_num == 0 and bg_num == 0:
+        fg_inds = paddle.zeros([0], dtype='int32')
+        bg_inds = paddle.zeros([0], dtype='int32')
+        return fg_inds, bg_inds
+
     # randomly select positive and negative examples
-    fg_perm = paddle.randperm(positive.numel(), dtype='int32')
-    fg_perm = paddle.slice(fg_perm, axes=[0], starts=[0], ends=[fg_num])
+
+    negative = negative.cast('int32').flatten()
     bg_perm = paddle.randperm(negative.numel(), dtype='int32')
     bg_perm = paddle.slice(bg_perm, axes=[0], starts=[0], ends=[bg_num])
     if use_random:
-        fg_inds = paddle.gather(positive, fg_perm)
         bg_inds = paddle.gather(negative, bg_perm)
     else:
-        fg_inds = paddle.slice(positive, axes=[0], starts=[0], ends=[fg_num])
         bg_inds = paddle.slice(negative, axes=[0], starts=[0], ends=[bg_num])
+    if fg_num == 0:
+        fg_inds = paddle.zeros([0], dtype='int32')
+        return fg_inds, bg_inds
+
+    positive = positive.cast('int32').flatten()
+    fg_perm = paddle.randperm(positive.numel(), dtype='int32')
+    fg_perm = paddle.slice(fg_perm, axes=[0], starts=[0], ends=[fg_num])
+    if use_random:
+        fg_inds = paddle.gather(positive, fg_perm)
+    else:
+        fg_inds = paddle.slice(positive, axes=[0], starts=[0], ends=[fg_num])
+
     return fg_inds, bg_inds
 
 
@@ -125,6 +175,8 @@ def generate_proposal_target(rpn_rois,
                              fg_thresh,
                              bg_thresh,
                              num_classes,
+                             ignore_thresh=-1.,
+                             is_crowd=None,
                              use_random=True,
                              is_cascade=False,
                              cascade_iou=0.5):
@@ -141,17 +193,18 @@ def generate_proposal_target(rpn_rois,
     bg_thresh = cascade_iou if is_cascade else bg_thresh
     for i, rpn_roi in enumerate(rpn_rois):
         gt_bbox = gt_boxes[i]
+        is_crowd_i = is_crowd[i] if is_crowd else None
         gt_class = paddle.squeeze(gt_classes[i], axis=-1)
 
-        # Concat RoIs and gt boxes except cascade rcnn
-        if not is_cascade:
+        # Concat RoIs and gt boxes except cascade rcnn or none gt
+        if not is_cascade and gt_bbox.shape[0] > 0:
             bbox = paddle.concat([rpn_roi, gt_bbox])
         else:
             bbox = rpn_roi
 
         # Step1: label bbox
         matches, match_labels = label_box(bbox, gt_bbox, fg_thresh, bg_thresh,
-                                          False)
+                                          False, ignore_thresh, is_crowd_i)
         # Step2: sample bbox 
         sampled_inds, sampled_gt_classes = sample_bbox(
             matches, match_labels, gt_class, batch_size_per_im, fg_fraction,
@@ -162,7 +215,10 @@ def generate_proposal_target(rpn_rois,
                                                                sampled_inds)
         sampled_gt_ind = matches if is_cascade else paddle.gather(matches,
                                                                   sampled_inds)
+        if gt_bbox.shape[0] > 0:
             sampled_bbox = paddle.gather(gt_bbox, sampled_gt_ind)
+        else:
+            sampled_bbox = paddle.zeros([0, 4], dtype='float32')
 
         rois_per_image.stop_gradient = True
         sampled_gt_ind.stop_gradient = True
@@ -184,6 +240,13 @@ def sample_bbox(matches,
                 num_classes,
                 use_random=True,
                 is_cascade=False):
+
+    n_gt = gt_classes.shape[0]
+    if n_gt == 0:
+        # No truth, assign everything to background
+        gt_classes = paddle.ones(matches.shape, dtype='int32') * num_classes
+        #return matches, match_labels + num_classes
+    else:
         gt_classes = paddle.gather(gt_classes, matches)
         gt_classes = paddle.where(match_labels == 0,
                                   paddle.ones_like(gt_classes) * num_classes,
@@ -191,11 +254,17 @@ def sample_bbox(matches,
         gt_classes = paddle.where(match_labels == -1,
                                   paddle.ones_like(gt_classes) * -1, gt_classes)
     if is_cascade:
-        return matches, gt_classes
+        index = paddle.arange(matches.shape[0])
+        return index, gt_classes
     rois_per_image = int(batch_size_per_im)
 
     fg_inds, bg_inds = subsample_labels(gt_classes, rois_per_image, fg_fraction,
                                         num_classes, use_random)
+    if fg_inds.shape[0] == 0 and bg_inds.shape[0] == 0:
+        # fake output labeled with -1 when all boxes are neither
+        # foreground nor background
+        sampled_inds = paddle.zeros([1], dtype='int32')
+    else:
         sampled_inds = paddle.concat([fg_inds, bg_inds])
     sampled_gt_classes = paddle.gather(gt_classes, sampled_inds)
     return sampled_inds, sampled_gt_classes
@@ -268,20 +337,29 @@ def generate_mask_target(gt_segms, rois, labels_int32, sampled_gt_inds,
         # to generate mask target with ground-truth
         boxes = fg_rois.numpy()
         gt_segms_per_im = gt_segms[k]
+
         new_segm = []
         inds_per_im = inds_per_im.numpy()
+        if len(gt_segms_per_im) > 0:
             for i in inds_per_im:
                 new_segm.append(gt_segms_per_im[i])
         fg_inds_new = fg_inds.reshape([-1]).numpy()
         results = []
+        if len(gt_segms_per_im) > 0:
             for j in fg_inds_new:
                 results.append(
                     rasterize_polygons_within_box(new_segm[j], boxes[j],
                                                   resolution))
+        else:
+            results.append(paddle.ones([resolution, resolution], dtype='int32'))
 
         fg_classes = paddle.gather(labels_per_im, fg_inds)
         weight = paddle.ones([fg_rois.shape[0]], dtype='float32')
         if not has_fg:
+            # now all sampled classes are background
+            # which will cause error in loss calculation,
+            # make fake classes with weight of 0.
+            fg_classes = paddle.zeros([1], dtype='int32')
             weight = weight - 1
         tgt_mask = paddle.stack(results)
         tgt_mask.stop_gradient = True

ppdet/modeling/proposal_generator/target_layer.py

@@ -44,6 +44,8 @@ class RPNTargetAssign(object):
         negative_overlap (float): Maximum overlap allowed between an anchor
             and ground-truth box for the (anchor, gt box) pair to be 
             a background sample. default 0.3
+        ignore_thresh(float): Threshold for ignoring the is_crowd ground-truth
+            if the value is larger than zero.
         use_random (bool): Use random sampling to choose foreground and 
             background boxes, default true.
     """
@@ -53,12 +55,14 @@ class RPNTargetAssign(object):
                  fg_fraction=0.5,
                  positive_overlap=0.7,
                  negative_overlap=0.3,
+                 ignore_thresh=-1.,
                  use_random=True):
         super(RPNTargetAssign, self).__init__()
         self.batch_size_per_im = batch_size_per_im
         self.fg_fraction = fg_fraction
         self.positive_overlap = positive_overlap
         self.negative_overlap = negative_overlap
+        self.ignore_thresh = ignore_thresh
         self.use_random = use_random
 
     def __call__(self, inputs, anchors):
@@ -67,11 +71,12 @@ class RPNTargetAssign(object):
         anchor_box (Tensor): [num_anchors, 4], num_anchors are all anchors in all feature maps.
         """
         gt_boxes = inputs['gt_bbox']
+        is_crowd = inputs.get('is_crowd', None)
         batch_size = len(gt_boxes)
         tgt_labels, tgt_bboxes, tgt_deltas = rpn_anchor_target(
             anchors, gt_boxes, self.batch_size_per_im, self.positive_overlap,
             self.negative_overlap, self.fg_fraction, self.use_random,
-            batch_size)
+            batch_size, self.ignore_thresh, is_crowd)
         norm = self.batch_size_per_im * batch_size
 
         return tgt_labels, tgt_bboxes, tgt_deltas, norm
@@ -101,6 +106,8 @@ class BBoxAssigner(object):
         bg_thresh (float): Maximum overlap allowed between a RoI
             and ground-truth box for the (roi, gt box) pair to be
             a background sample. default 0.5
+        ignore_thresh(float): Threshold for ignoring the is_crowd ground-truth
+            if the value is larger than zero.
         use_random (bool): Use random sampling to choose foreground and 
             background boxes, default true
         cascade_iou (list[iou]): The list of overlap to select foreground and
@@ -113,6 +120,7 @@ class BBoxAssigner(object):
                  fg_fraction=.25,
                  fg_thresh=.5,
                  bg_thresh=.5,
+                 ignore_thresh=-1.,
                  use_random=True,
                  cascade_iou=[0.5, 0.6, 0.7],
                  num_classes=80):
@@ -121,6 +129,7 @@ class BBoxAssigner(object):
         self.fg_fraction = fg_fraction
         self.fg_thresh = fg_thresh
         self.bg_thresh = bg_thresh
+        self.ignore_thresh = ignore_thresh
         self.use_random = use_random
         self.cascade_iou = cascade_iou
         self.num_classes = num_classes
@@ -133,12 +142,14 @@ class BBoxAssigner(object):
                  is_cascade=False):
         gt_classes = inputs['gt_class']
         gt_boxes = inputs['gt_bbox']
+        is_crowd = inputs.get('is_crowd', None)
         # rois, tgt_labels, tgt_bboxes, tgt_gt_inds
         # new_rois_num
         outs = generate_proposal_target(
             rpn_rois, gt_classes, gt_boxes, self.batch_size_per_im,
             self.fg_fraction, self.fg_thresh, self.bg_thresh, self.num_classes,
-            self.use_random, is_cascade, self.cascade_iou[stage])
+            self.ignore_thresh, is_crowd, self.use_random, is_cascade,
+            self.cascade_iou[stage])
         rois = outs[0]
         rois_num = outs[-1]
         # tgt_labels, tgt_bboxes, tgt_gt_inds