# coding=utf-8

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import os
import unittest
from parameterized import parameterized

import torch
import torch.nn.functional as F
import torch.distributed as dist
import torch_harmonics as harmonics
import torch_harmonics.distributed as thd


class TestDistributedResampling(unittest.TestCase):

    @classmethod
    def setUpClass(cls):

        # set up distributed
        cls.world_rank = int(os.getenv("WORLD_RANK", 0))
        cls.grid_size_h = int(os.getenv("GRID_H", 1))
        cls.grid_size_w = int(os.getenv("GRID_W", 1))
        port = int(os.getenv("MASTER_PORT", "29501"))
        master_address = os.getenv("MASTER_ADDR", "localhost")
        cls.world_size = cls.grid_size_h * cls.grid_size_w

        if torch.cuda.is_available():
            if cls.world_rank == 0:
                print("Running test on GPU")
            local_rank = cls.world_rank % torch.cuda.device_count()
            cls.device = torch.device(f"cuda:{local_rank}")
            torch.cuda.set_device(local_rank)
            torch.cuda.manual_seed(333)
            proc_backend = "nccl"
        else:
            if cls.world_rank == 0:
                print("Running test on CPU")
            cls.device = torch.device("cpu")
            proc_backend = "gloo"
        torch.manual_seed(333)

        dist.init_process_group(backend=proc_backend, init_method=f"tcp://{master_address}:{port}", rank=cls.world_rank, world_size=cls.world_size)

        cls.wrank = cls.world_rank % cls.grid_size_w
        cls.hrank = cls.world_rank // cls.grid_size_w

        # now set up the comm groups:
        # set default
        cls.w_group = None
        cls.h_group = None

        # do the init
        wgroups = []
        for w in range(0, cls.world_size, cls.grid_size_w):
            start = w
            end = w + cls.grid_size_w
            wgroups.append(list(range(start, end)))

        if cls.world_rank == 0:
            print("w-groups:", wgroups)
        for grp in wgroups:
            if len(grp) == 1:
                continue
            tmp_group = dist.new_group(ranks=grp)
            if cls.world_rank in grp:
                cls.w_group = tmp_group

        # transpose:
        hgroups = [sorted(list(i)) for i in zip(*wgroups)]

        if cls.world_rank == 0:
            print("h-groups:", hgroups)
        for grp in hgroups:
            if len(grp) == 1:
                continue
            tmp_group = dist.new_group(ranks=grp)
            if cls.world_rank in grp:
                cls.h_group = tmp_group

        if cls.world_rank == 0:
            print(f"Running distributed tests on grid H x W = {cls.grid_size_h} x {cls.grid_size_w}")

        # initializing sht
        thd.init(cls.h_group, cls.w_group)

    @classmethod
    def tearDownClass(cls):
        thd.finalize()
        dist.destroy_process_group(None)

    def _split_helper(self, tensor):
        with torch.no_grad():
            # split in W
            tensor_list_local = thd.split_tensor_along_dim(tensor, dim=-1, num_chunks=self.grid_size_w)
            tensor_local = tensor_list_local[self.wrank]

            # split in H
            tensor_list_local = thd.split_tensor_along_dim(tensor_local, dim=-2, num_chunks=self.grid_size_h)
            tensor_local = tensor_list_local[self.hrank]

        return tensor_local

    def _gather_helper_fwd(self, tensor, B, C, convolution_dist):
        # we need the shapes
        lat_shapes = convolution_dist.lat_out_shapes
        lon_shapes = convolution_dist.lon_out_shapes

        # gather in W
        tensor = tensor.contiguous()
        if self.grid_size_w > 1:
            gather_shapes = [(B, C, lat_shapes[self.hrank], w) for w in lon_shapes]
            olist = [torch.empty(shape, dtype=tensor.dtype, device=tensor.device) for shape in gather_shapes]
            olist[self.wrank] = tensor
            dist.all_gather(olist, tensor, group=self.w_group)
            tensor_gather = torch.cat(olist, dim=-1)
        else:
            tensor_gather = tensor

        # gather in H
        tensor_gather = tensor_gather.contiguous()
        if self.grid_size_h > 1:
            gather_shapes = [(B, C, h, convolution_dist.nlon_out) for h in lat_shapes]
            olist = [torch.empty(shape, dtype=tensor_gather.dtype, device=tensor_gather.device) for shape in gather_shapes]
            olist[self.hrank] = tensor_gather
            dist.all_gather(olist, tensor_gather, group=self.h_group)
            tensor_gather = torch.cat(olist, dim=-2)

        return tensor_gather

    def _gather_helper_bwd(self, tensor, B, C, resampling_dist):
        # we need the shapes
        lat_shapes = resampling_dist.lat_in_shapes
        lon_shapes = resampling_dist.lon_in_shapes

        # gather in W
        if self.grid_size_w > 1:
            gather_shapes = [(B, C, lat_shapes[self.hrank], w) for w in lon_shapes]
            olist = [torch.empty(shape, dtype=tensor.dtype, device=tensor.device) for shape in gather_shapes]
            olist[self.wrank] = tensor
            dist.all_gather(olist, tensor, group=self.w_group)
            tensor_gather = torch.cat(olist, dim=-1)
        else:
            tensor_gather = tensor

        # gather in H
        if self.grid_size_h > 1:
            gather_shapes = [(B, C, h, resampling_dist.nlon_in) for h in lat_shapes]
            olist = [torch.empty(shape, dtype=tensor_gather.dtype, device=tensor_gather.device) for shape in gather_shapes]
            olist[self.hrank] = tensor_gather
            dist.all_gather(olist, tensor_gather, group=self.h_group)
            tensor_gather = torch.cat(olist, dim=-2)

        return tensor_gather

    @parameterized.expand(
        [
            [64, 128, 128, 256, 32, 8, "equiangular", "equiangular", 1e-7],
            [128, 256, 64, 128, 32, 8, "equiangular", "equiangular", 1e-7],
        ]
    )
    def test_distributed_resampling(
        self, nlat_in, nlon_in, nlat_out, nlon_out, batch_size, num_chan, grid_in, grid_out, tol
    ):

        B, C, H, W = batch_size, num_chan, nlat_in, nlon_in

        res_args = dict(
            nlat_in=nlat_in, 
            nlon_in=nlon_in,
            nlat_out=nlat_out, 
            nlon_out=nlon_out,
            grid_in=grid_in,
            grid_out=grid_out,
        )

        # set up handlesD
        res_local = harmonics.ResampleS2(**res_args).to(self.device)
        res_dist = thd.DistributedResampleS2(**res_args).to(self.device)

        # create tensors
        inp_full = torch.randn((B, C, H, W), dtype=torch.float32, device=self.device)

        #############################################################
        # local conv
        #############################################################
        # FWD pass
        inp_full.requires_grad = True
        out_full = res_local(inp_full)

        # create grad for backward
        with torch.no_grad():
            # create full grad
            ograd_full = torch.randn_like(out_full)

        # BWD pass
        out_full.backward(ograd_full)
        igrad_full = inp_full.grad.clone()

        #############################################################
        # distributed conv
        #############################################################
        # FWD pass
        inp_local = self._split_helper(inp_full)
        inp_local.requires_grad = True
        out_local = res_dist(inp_local)

        # BWD pass
        ograd_local = self._split_helper(ograd_full)
        out_local = res_dist(inp_local)
        out_local.backward(ograd_local)
        igrad_local = inp_local.grad.clone()

        #############################################################
        # evaluate FWD pass
        #############################################################
        with torch.no_grad():
            out_gather_full = self._gather_helper_fwd(out_local, B, C, res_dist)
            err = torch.mean(torch.norm(out_full - out_gather_full, p="fro", dim=(-1, -2)) / torch.norm(out_full, p="fro", dim=(-1, -2)))
            if self.world_rank == 0:
                print(f"final relative error of output: {err.item()}")
        self.assertTrue(err.item() <= tol)

        #############################################################
        # evaluate BWD pass
        #############################################################
        with torch.no_grad():
            igrad_gather_full = self._gather_helper_bwd(igrad_local, B, C, res_dist)

            err = torch.mean(torch.norm(igrad_full - igrad_gather_full, p="fro", dim=(-1, -2)) / torch.norm(igrad_full, p="fro", dim=(-1, -2)))
            if self.world_rank == 0:
                print(f"final relative error of gradients: {err.item()}")
        self.assertTrue(err.item() <= tol)


if __name__ == "__main__":
    unittest.main()
