//  [python]
def fasterquant(
        self, W, blocksize=128, percdamp=0.01, groupsize=-1, act_order=False
    ):
        weight_shape, weight_dtype = W.shape, W.data.dtype
        if isinstance(self.layer, nn.Conv2d):
            W = W.flatten(1)
        if isinstance(self.layer, transformers.Conv1D):
            W = W.t()
        W = W.float()

        tick = time.time()

        if not self.quantizer.ready():
            self.quantizer.find_params(W, weight=True)

        H = self.H
        del self.H
        dead = torch.diag(H) == 0
        H[dead, dead] = 1
        W[:, dead] = 0  # such channel makes no contribution to quantization computation

        # rearrange considering the diag's value
        if act_order:
            perm = torch.argsort(torch.diag(H), descending=True)
            W = W[:, perm]
            H = H[perm][:, perm]
            self.perm = perm.clone()

        Losses = torch.zeros_like(W)
        Q = torch.zeros_like(W)

        damp = percdamp * torch.mean(torch.diag(H))
        diag = torch.arange(self.columns, device=self.device)
        H[diag, diag] += damp
        H = torch.cholesky(H)
        H = torch.cholesky_inverse(H)
        H = torch.cholesky(H, upper=True)
        Hinv = H

        scale = []
        zero = []

        for i1 in range(0, self.columns, blocksize):
            i2 = min(i1 + blocksize, self.columns)
            count = i2 - i1

            W1 = W[:, i1:i2].clone()
            Q1 = torch.zeros_like(W1)
            Err1 = torch.zeros_like(W1)
            Losses1 = torch.zeros_like(W1)
            Hinv1 = Hinv[i1:i2, i1:i2]

            for i in range(count):  # within a block, channel wise
                w = W1[:, i]
                d = Hinv1[i, i]

                if groupsize != -1:
                    if (i1 + i) % groupsize == 0:
                        self.quantizer.find_params(
                            W[:, (i1 + i) : (i1 + i + groupsize)], weight=True
                        )
                        scale.append(self.quantizer.scale)
                        zero.append(self.quantizer.zero)

                q = quantize(
                    w.unsqueeze(1),
                    self.quantizer.scale,
                    self.quantizer.zero,
                    self.quantizer.maxq,
                ).flatten()
                Q1[:, i] = q
                Losses1[:, i] = (w - q) ** 2 / d**2

                err1 = (w - q) / d
                W1[:, i:] -= err1.unsqueeze(1).matmul(Hinv1[i, i:].unsqueeze(0))
                Err1[:, i] = err1

            Q[:, i1:i2] = Q1
            Losses[:, i1:i2] = Losses1 / 2

            W[:, i2:] -= Err1.matmul(Hinv[i1:i2, i2:])

        # logger.info(f"time {(time.time() - tick)}")
        # logger.info(f"error {torch.sum(Losses).item()}")

        if act_order:
            invperm = torch.argsort(perm)
            Q = Q[:, invperm]

        if isinstance(self.layer, transformers.Conv1D):
            Q = Q.t()
        # self.layer.weight.data = Q.reshape(self.layer.weight.shape).to(self.layer.weight.data.dtype)
        Q = Q.reshape(weight_shape).to(weight_dtype)
        if DEBUG:
            logger.info(f"{torch.sum((self.layer(self.inp1) - self.out1) ** 2)}")

        if scale == []:
            scale.append(self.quantizer.scale)
            zero.append(self.quantizer.zero)
        scale = torch.cat(scale, dim=1)
        zero = torch.cat(zero, dim=1)
        return scale, zero, Q