Based on this plot below, I think SSD predicts the classes and bounding boxes of anchor boxes (based on the , so I expect the anchor boxes generated by multibox_prior should be explicitly passed into cls_predictor and bbox_predictor.
However, in blk_forward, only the feature map Y are passed in:
def blk_forward(X, blk, size, ratio, cls_predictor, bbox_predictor):
Y = blk(X)
anchors = d2l.multibox_prior(Y, sizes=size, ratios=ratio)
cls_preds = cls_predictor(Y)
bbox_preds = bbox_predictor(Y)
return (Y, anchors, cls_preds, bbox_preds)
So, the SSD model forward propogation outputs classes & labels solely based on feature maps. The anchor boxes are only used during the loss evaluation. Is this statement correct?
Thanks for any correction & thoughts!
