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| def accuracy(pred, target, topk=1, thresh=None): | |
| """Calculate accuracy according to the prediction and target. | |
| Args: | |
| pred (torch.Tensor): The model prediction, shape (N, num_class, ...) | |
| target (torch.Tensor): The target of each prediction, shape (N, , ...) | |
| topk (int | tuple[int], optional): If the predictions in ``topk`` | |
| matches the target, the predictions will be regarded as | |
| correct ones. Defaults to 1. | |
| thresh (float, optional): If not None, predictions with scores under | |
| this threshold are considered incorrect. Default to None. | |
| Returns: | |
| float | tuple[float]: If the input ``topk`` is a single integer, | |
| the function will return a single float as accuracy. If | |
| ``topk`` is a tuple containing multiple integers, the | |
| function will return a tuple containing accuracies of | |
| each ``topk`` number. | |
| """ | |
| assert isinstance(topk, (int, tuple)) | |
| if isinstance(topk, int): | |
| topk = (topk, ) | |
| return_single = True | |
| else: | |
| return_single = False | |
| maxk = max(topk) | |
| if pred.size(0) == 0: | |
| accu = [pred.new_tensor(0.) for i in range(len(topk))] | |
| return accu[0] if return_single else accu | |
| assert pred.ndim == target.ndim + 1 | |
| assert pred.size(0) == target.size(0) | |
| assert maxk <= pred.size(1), \ | |
| f'maxk {maxk} exceeds pred dimension {pred.size(1)}' | |
| pred_value, pred_label = pred.topk(maxk, dim=1) | |
| # transpose to shape (maxk, N, ...) | |
| pred_label = pred_label.transpose(0, 1) | |
| correct = pred_label.eq(target.unsqueeze(0).expand_as(pred_label)) | |
| if thresh is not None: | |
| # Only prediction values larger than thresh are counted as correct | |
| correct = correct & (pred_value > thresh).t() | |
| res = [] | |
| for k in topk: | |
| correct_k = correct[:k].view(-1).float().sum(0, keepdim=True) | |
| res.append(correct_k.mul_(100.0 / target.numel())) | |
| return res[0] if return_single else res | |