third_party/SGMNet/sgmnet/match_model.py

import torch
import torch.nn as nn

eps = 1e-8

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

def sinkhorn(M, r, c, iteration):
    p = torch.softmax(M, dim=-1)
    u = torch.ones_like(r)
    v = torch.ones_like(c)
    for _ in range(iteration):
        u = r / ((p * v.unsqueeze(-2)).sum(-1) + eps)
        v = c / ((p * u.unsqueeze(-1)).sum(-2) + eps)
    p = p * u.unsqueeze(-1) * v.unsqueeze(-2)
    return p


def sink_algorithm(M, dustbin, iteration):
    M = torch.cat([M, dustbin.expand([M.shape[0], M.shape[1], 1])], dim=-1)
    M = torch.cat([M, dustbin.expand([M.shape[0], 1, M.shape[2]])], dim=-2)
    r = torch.ones([M.shape[0], M.shape[1] - 1], device=device)
    r = torch.cat([r, torch.ones([M.shape[0], 1], device=device) * M.shape[1]], dim=-1)
    c = torch.ones([M.shape[0], M.shape[2] - 1], device=device)
    c = torch.cat([c, torch.ones([M.shape[0], 1], device=device) * M.shape[2]], dim=-1)
    p = sinkhorn(M, r, c, iteration)
    return p


def seeding(
    nn_index1,
    nn_index2,
    x1,
    x2,
    topk,
    match_score,
    confbar,
    nms_radius,
    use_mc=True,
    test=False,
):

    # apply mutual check before nms
    if use_mc:
        mask_not_mutual = nn_index2.gather(dim=-1, index=nn_index1) != torch.arange(
            nn_index1.shape[1], device=device
        )
        match_score[mask_not_mutual] = -1
    # NMS
    pos_dismat1 = (
        (
            (x1.norm(p=2, dim=-1) ** 2).unsqueeze_(-1)
            + (x1.norm(p=2, dim=-1) ** 2).unsqueeze_(-2)
            - 2 * (x1 @ x1.transpose(1, 2))
        )
        .abs_()
        .sqrt_()
    )
    x2 = x2.gather(index=nn_index1.unsqueeze(-1).expand(-1, -1, 2), dim=1)
    pos_dismat2 = (
        (
            (x2.norm(p=2, dim=-1) ** 2).unsqueeze_(-1)
            + (x2.norm(p=2, dim=-1) ** 2).unsqueeze_(-2)
            - 2 * (x2 @ x2.transpose(1, 2))
        )
        .abs_()
        .sqrt_()
    )
    radius1, radius2 = nms_radius * pos_dismat1.mean(
        dim=(1, 2), keepdim=True
    ), nms_radius * pos_dismat2.mean(dim=(1, 2), keepdim=True)
    nms_mask = (pos_dismat1 >= radius1) & (pos_dismat2 >= radius2)
    mask_not_local_max = (
        match_score.unsqueeze(-1) >= match_score.unsqueeze(-2)
    ) | nms_mask
    mask_not_local_max = ~(mask_not_local_max.min(dim=-1).values)
    match_score[mask_not_local_max] = -1

    # confidence bar
    match_score[match_score < confbar] = -1
    mask_survive = match_score > 0
    if test:
        topk = min(mask_survive.sum(dim=1)[0] + 2, topk)
    _, topindex = torch.topk(match_score, topk, dim=-1)  # b*k
    seed_index1, seed_index2 = topindex, nn_index1.gather(index=topindex, dim=-1)
    return seed_index1, seed_index2


class PointCN(nn.Module):
    def __init__(self, channels, out_channels):
        nn.Module.__init__(self)
        self.shot_cut = nn.Conv1d(channels, out_channels, kernel_size=1)
        self.conv = nn.Sequential(
            nn.InstanceNorm1d(channels, eps=1e-3),
            nn.SyncBatchNorm(channels),
            nn.ReLU(),
            nn.Conv1d(channels, channels, kernel_size=1),
            nn.InstanceNorm1d(channels, eps=1e-3),
            nn.SyncBatchNorm(channels),
            nn.ReLU(),
            nn.Conv1d(channels, out_channels, kernel_size=1),
        )

    def forward(self, x):
        return self.conv(x) + self.shot_cut(x)


class attention_propagantion(nn.Module):
    def __init__(self, channel, head):
        nn.Module.__init__(self)
        self.head = head
        self.head_dim = channel // head
        self.query_filter, self.key_filter, self.value_filter = (
            nn.Conv1d(channel, channel, kernel_size=1),
            nn.Conv1d(channel, channel, kernel_size=1),
            nn.Conv1d(channel, channel, kernel_size=1),
        )
        self.mh_filter = nn.Conv1d(channel, channel, kernel_size=1)
        self.cat_filter = nn.Sequential(
            nn.Conv1d(2 * channel, 2 * channel, kernel_size=1),
            nn.SyncBatchNorm(2 * channel),
            nn.ReLU(),
            nn.Conv1d(2 * channel, channel, kernel_size=1),
        )

    def forward(self, desc1, desc2, weight_v=None):
        # desc1(q) attend to desc2(k,v)
        batch_size = desc1.shape[0]
        query, key, value = (
            self.query_filter(desc1).view(batch_size, self.head, self.head_dim, -1),
            self.key_filter(desc2).view(batch_size, self.head, self.head_dim, -1),
            self.value_filter(desc2).view(batch_size, self.head, self.head_dim, -1),
        )
        if weight_v is not None:
            value = value * weight_v.view(batch_size, 1, 1, -1)
        score = torch.softmax(
            torch.einsum("bhdn,bhdm->bhnm", query, key) / self.head_dim**0.5, dim=-1
        )
        add_value = torch.einsum("bhnm,bhdm->bhdn", score, value).reshape(
            batch_size, self.head_dim * self.head, -1
        )
        add_value = self.mh_filter(add_value)
        desc1_new = desc1 + self.cat_filter(torch.cat([desc1, add_value], dim=1))
        return desc1_new


class hybrid_block(nn.Module):
    def __init__(self, channel, head):
        nn.Module.__init__(self)
        self.head = head
        self.channel = channel
        self.attention_block_down = attention_propagantion(channel, head)
        self.cluster_filter = nn.Sequential(
            nn.Conv1d(2 * channel, 2 * channel, kernel_size=1),
            nn.SyncBatchNorm(2 * channel),
            nn.ReLU(),
            nn.Conv1d(2 * channel, 2 * channel, kernel_size=1),
        )
        self.cross_filter = attention_propagantion(channel, head)
        self.confidence_filter = PointCN(2 * channel, 1)
        self.attention_block_self = attention_propagantion(channel, head)
        self.attention_block_up = attention_propagantion(channel, head)

    def forward(self, desc1, desc2, seed_index1, seed_index2):
        cluster1, cluster2 = desc1.gather(
            dim=-1, index=seed_index1.unsqueeze(1).expand(-1, self.channel, -1)
        ), desc2.gather(
            dim=-1, index=seed_index2.unsqueeze(1).expand(-1, self.channel, -1)
        )

        # pooling
        cluster1, cluster2 = self.attention_block_down(
            cluster1, desc1
        ), self.attention_block_down(cluster2, desc2)
        concate_cluster = self.cluster_filter(torch.cat([cluster1, cluster2], dim=1))
        # filtering
        cluster1, cluster2 = self.cross_filter(
            concate_cluster[:, : self.channel], concate_cluster[:, self.channel :]
        ), self.cross_filter(
            concate_cluster[:, self.channel :], concate_cluster[:, : self.channel]
        )
        cluster1, cluster2 = self.attention_block_self(
            cluster1, cluster1
        ), self.attention_block_self(cluster2, cluster2)
        # unpooling
        seed_weight = self.confidence_filter(torch.cat([cluster1, cluster2], dim=1))
        seed_weight = torch.sigmoid(seed_weight).squeeze(1)
        desc1_new, desc2_new = self.attention_block_up(
            desc1, cluster1, seed_weight
        ), self.attention_block_up(desc2, cluster2, seed_weight)
        return desc1_new, desc2_new, seed_weight


class matcher(nn.Module):
    def __init__(self, config):
        nn.Module.__init__(self)
        self.seed_top_k = config.seed_top_k
        self.conf_bar = config.conf_bar
        self.seed_radius_coe = config.seed_radius_coe
        self.use_score_encoding = config.use_score_encoding
        self.detach_iter = config.detach_iter
        self.seedlayer = config.seedlayer
        self.layer_num = config.layer_num
        self.sink_iter = config.sink_iter

        self.position_encoder = nn.Sequential(
            nn.Conv1d(3, 32, kernel_size=1)
            if config.use_score_encoding
            else nn.Conv1d(2, 32, kernel_size=1),
            nn.SyncBatchNorm(32),
            nn.ReLU(),
            nn.Conv1d(32, 64, kernel_size=1),
            nn.SyncBatchNorm(64),
            nn.ReLU(),
            nn.Conv1d(64, 128, kernel_size=1),
            nn.SyncBatchNorm(128),
            nn.ReLU(),
            nn.Conv1d(128, 256, kernel_size=1),
            nn.SyncBatchNorm(256),
            nn.ReLU(),
            nn.Conv1d(256, config.net_channels, kernel_size=1),
        )

        self.hybrid_block = nn.Sequential(
            *[
                hybrid_block(config.net_channels, config.head)
                for _ in range(config.layer_num)
            ]
        )
        self.final_project = nn.Conv1d(
            config.net_channels, config.net_channels, kernel_size=1
        )
        self.dustbin = nn.Parameter(torch.tensor(1.5, dtype=torch.float32))

        # if reseeding
        if len(config.seedlayer) != 1:
            self.mid_dustbin = nn.ParameterDict(
                {
                    str(i): nn.Parameter(torch.tensor(2, dtype=torch.float32))
                    for i in config.seedlayer[1:]
                }
            )
            self.mid_final_project = nn.Conv1d(
                config.net_channels, config.net_channels, kernel_size=1
            )

    def forward(self, data, test_mode=True):
        x1, x2, desc1, desc2 = (
            data["x1"][:, :, :2],
            data["x2"][:, :, :2],
            data["desc1"],
            data["desc2"],
        )
        desc1, desc2 = torch.nn.functional.normalize(
            desc1, dim=-1
        ), torch.nn.functional.normalize(desc2, dim=-1)
        if test_mode:
            encode_x1, encode_x2 = data["x1"], data["x2"]
        else:
            encode_x1, encode_x2 = data["aug_x1"], data["aug_x2"]

        # preparation
        desc_dismat = (2 - 2 * torch.matmul(desc1, desc2.transpose(1, 2))).sqrt_()
        values, nn_index = torch.topk(
            desc_dismat, k=2, largest=False, dim=-1, sorted=True
        )
        nn_index2 = torch.min(desc_dismat, dim=1).indices.squeeze(1)
        inverse_ratio_score, nn_index1 = (
            values[:, :, 1] / values[:, :, 0],
            nn_index[:, :, 0],
        )  # get inverse score

        # initial seeding
        seed_index1, seed_index2 = seeding(
            nn_index1,
            nn_index2,
            x1,
            x2,
            self.seed_top_k[0],
            inverse_ratio_score,
            self.conf_bar[0],
            self.seed_radius_coe,
            test=test_mode,
        )

        # position encoding
        desc1, desc2 = desc1.transpose(1, 2), desc2.transpose(1, 2)
        if not self.use_score_encoding:
            encode_x1, encode_x2 = encode_x1[:, :, :2], encode_x2[:, :, :2]
        encode_x1, encode_x2 = encode_x1.transpose(1, 2), encode_x2.transpose(1, 2)
        x1_pos_embedding, x2_pos_embedding = self.position_encoder(
            encode_x1
        ), self.position_encoder(encode_x2)
        aug_desc1, aug_desc2 = x1_pos_embedding + desc1, x2_pos_embedding + desc2

        seed_weight_tower, mid_p_tower, seed_index_tower, nn_index_tower = (
            [],
            [],
            [],
            [],
        )
        seed_index_tower.append(torch.stack([seed_index1, seed_index2], dim=-1))
        nn_index_tower.append(nn_index1)

        seed_para_index = 0
        for i in range(self.layer_num):
            # mid seeding
            if i in self.seedlayer and i != 0:
                seed_para_index += 1
                aug_desc1, aug_desc2 = self.mid_final_project(
                    aug_desc1
                ), self.mid_final_project(aug_desc2)
                M = torch.matmul(aug_desc1.transpose(1, 2), aug_desc2)
                p = sink_algorithm(
                    M, self.mid_dustbin[str(i)], self.sink_iter[seed_para_index - 1]
                )
                mid_p_tower.append(p)
                # rematching with p
                values, nn_index = torch.topk(p[:, :-1, :-1], k=1, dim=-1)
                nn_index2 = torch.max(p[:, :-1, :-1], dim=1).indices.squeeze(1)
                p_match_score, nn_index1 = values[:, :, 0], nn_index[:, :, 0]
                # reseeding
                seed_index1, seed_index2 = seeding(
                    nn_index1,
                    nn_index2,
                    x1,
                    x2,
                    self.seed_top_k[seed_para_index],
                    p_match_score,
                    self.conf_bar[seed_para_index],
                    self.seed_radius_coe,
                    test=test_mode,
                )
                seed_index_tower.append(
                    torch.stack([seed_index1, seed_index2], dim=-1)
                ), nn_index_tower.append(nn_index1)
                if not test_mode and data["step"] < self.detach_iter:
                    aug_desc1, aug_desc2 = aug_desc1.detach(), aug_desc2.detach()

            aug_desc1, aug_desc2, seed_weight = self.hybrid_block[i](
                aug_desc1, aug_desc2, seed_index1, seed_index2
            )
            seed_weight_tower.append(seed_weight)

        aug_desc1, aug_desc2 = self.final_project(aug_desc1), self.final_project(
            aug_desc2
        )
        cmat = torch.matmul(aug_desc1.transpose(1, 2), aug_desc2)
        p = sink_algorithm(cmat, self.dustbin, self.sink_iter[-1])
        # seed_weight_tower: l*b*k
        # seed_index_tower: l*b*k*2
        # nn_index_tower: seed_l*b
        return {
            "p": p,
            "seed_conf": seed_weight_tower,
            "seed_index": seed_index_tower,
            "mid_p": mid_p_tower,
            "nn_index": nn_index_tower,
        }