error.py 文件源码

def forward_cpu(self, inputs):
        x, t = inputs
        if chainer.is_debug():
            self._check_input_values(x, t)

        log_y = log_softmax._log_softmax(x)
        if self.cache_score:
            self.y = np.exp(log_y)
        if self.class_weight is not None:
            shape = [1 if d != 1 else -1 for d in six.moves.range(x.ndim)]
            log_y *= _broadcast_to(self.class_weight.reshape(shape), x.shape)
        log_yd = np.rollaxis(log_y, 1)
        log_yd = log_yd.reshape(len(log_yd), -1)
        log_p = log_yd[np.maximum(t.ravel(), 0), np.arange(t.size)]

        log_p *= (t.ravel() != self.ignore_label)
        if self.reduce == 'mean':
            # deal with the case where the SoftmaxCrossEntropy is
            # unpickled from the old version
            if self.normalize:
                count = (t != self.ignore_label).sum()
            else:
                count = len(x)
            self._coeff = 1.0 / max(count, 1)

            y = log_p.sum(keepdims=True) * (-self._coeff)
            return y.reshape(()),
        else:
            return -log_p.reshape(t.shape),