import torch
import torch.nn as nn
from torch.utils.cpp_extension import load_inline

class ModelNew(nn.Module):
    def __init__(self, tl=-1.0, al=0.1, tr=1.0, ar=0.1):
        super().__init__()
        self.tl = tl
        self.al = al
        self.tr = tr
        self.ar = ar
        self._compile_cuda_kernel()

    def _compile_cuda_kernel(self):
        cpp_source = """
        torch::Tensor srelu_cuda(torch::Tensor x, float tl, float al, float tr, float ar);
        """

        cuda_source = """
        #include <torch/extension.h>
        #include <cuda_runtime.h>
        #include <math.h>

        __device__ __forceinline__ float srelu_op(float x, float tl, float al, float tr, float ar) {
            // Region 1: x <= t_l
            if (x <= tl) {
                return tl + al * (x - tl);
            }
            // Region 3: x >= t_r
            if (x >= tr) {
                return tr + ar * (x - tr);
            }
            // Region 2: t_l < x < t_r
            return x;
        }

        __global__ void srelu_kernel(
            const float* __restrict__ x,
            float* __restrict__ output,
            const int n_elements,
            const float tl,
            const float al,
            const float tr,
            const float ar) 
        {
            const int tid = blockIdx.x * blockDim.x + threadIdx.x;
            const int stride = blockDim.x * gridDim.x;

            const int vec_loops = n_elements >> 2;
            const float4* x_vec = reinterpret_cast<const float4*>(x);
            float4* out_vec = reinterpret_cast<float4*>(output);

            for (int i = tid; i < vec_loops; i += stride) {
                float4 v = __ldg(&x_vec[i]);
                float4 r;

                r.x = srelu_op(v.x, tl, al, tr, ar);
                r.y = srelu_op(v.y, tl, al, tr, ar);
                r.z = srelu_op(v.z, tl, al, tr, ar);
                r.w = srelu_op(v.w, tl, al, tr, ar);

                out_vec[i] = r;
            }

            const int tail_start = vec_loops << 2;
            for (int i = tail_start + tid; i < n_elements; i += stride) {
                output[i] = srelu_op(x[i], tl, al, tr, ar);
            }
        }

        torch::Tensor srelu_cuda(torch::Tensor x, float tl, float al, float tr, float ar) {
            auto x_c = x.contiguous();
            const int n_elements = x_c.numel();
            auto output = torch::empty_like(x_c);

            const int threads = 256;
            const int max_blocks = 65535;
            const int blocks = std::min((n_elements + threads * 4 - 1) / (threads * 4), max_blocks);

            srelu_kernel<<<blocks, threads>>>(
                x_c.data_ptr<float>(),
                output.data_ptr<float>(),
                n_elements,
                tl, al, tr, ar
            );

            return output;
        }
        """

        self.op = load_inline(
            name="srelu_v1",
            cpp_sources=cpp_source,
            cuda_sources=cuda_source,
            functions=["srelu_cuda"],
            extra_cuda_cflags=["-O3", "--use_fast_math"],
            verbose=False
        )

    def forward(self, x):
        return self.op.srelu_cuda(x, self.tl, self.al, self.tr, self.ar)