"""Test: Validate that cute.exp works on register tensors in the fused epilogue.

Step 1 of the fused SwiGLU validation. We test with fused_swiglu=True but
with the full SiLU applied (not gate/up pairing yet). This confirms that:
1. cute.exp works on register tensors
2. The element-wise SiLU (x / (1+exp(-x))) produces correct values
3. The register tensor can be converted to BF16 and stored to C

The test compares the fused kernel output (SiLU applied in registers)
against the PyTorch equivalent (SiLU applied to the BF16 L1 output).
"""
import torch
import sys
sys.path.insert(0, '/root/dsv4-nvfp4-workspace/kernel')

from dsv4.ops.quantize import (
    quantize_weight_to_nvfp4,
    quantize_activation_nvfp4,
)
from dsv4.ops.layouts import (
    make_b_k_major,
    assemble_scales_2d_side,
    assemble_scales_3d_side,
)
from dsv4.ops.gemm_runner import (
    run_nvfp4_grouped_gemm,
    warmup_compilation,
)


def test_silu_in_registers():
    """Compare SiLU applied in registers vs SiLU applied in PyTorch."""
    device = "cuda"
    num_experts = 4
    hidden = 512
    intermediate = 256
    num_tokens = 32

    torch.manual_seed(42)
    x = torch.randn(num_tokens, hidden, dtype=torch.bfloat16, device=device)
    
    # Create and quantize L1 weights (gate+up fused)
    l1_w = torch.randn(num_experts, 2 * intermediate, hidden, dtype=torch.bfloat16, device=device)
    l1_fp4_list, l1_sf_list, l1_gs_list = [], [], []
    for e in range(num_experts):
        w_fp4, w_sf, w_gs = quantize_weight_to_nvfp4(l1_w[e].T)
        l1_fp4_list.append(w_fp4)
        l1_sf_list.append(w_sf)
        l1_gs_list.append(w_gs)

    l1_mat_b = make_b_k_major(torch.stack(l1_fp4_list))
    l1_scale_b = assemble_scales_3d_side(l1_sf_list)
    l1_gs = torch.tensor(l1_gs_list, dtype=torch.float32, device=device)

    gs_val = x.abs().max().item() / (6.0 * 448.0)
    x_fp4, x_sf = quantize_activation_nvfp4(x, gs_val)

    tokens_per_expert = [num_tokens // num_experts] * num_experts
    scale_a = assemble_scales_2d_side([x_sf[i*tpe:(i+1)*tpe] for i, tpe in enumerate(tokens_per_expert)])
    expert_offsets = torch.tensor(
        [sum(tokens_per_expert[:e+1]) for e in range(num_experts)],
        dtype=torch.int32, device=device,
    )
    global_scale_a = torch.full((num_experts,), gs_val, dtype=torch.float32, device=device)

    # Warmup standard GEMM
    warmup_compilation(num_experts, hidden // 2, (2 * intermediate) // 2, device)

    # Run standard L1 GEMM (no SiLU)
    out_bf16 = run_nvfp4_grouped_gemm(
        mat_a=x_fp4, mat_b=l1_mat_b,
        scale_a=scale_a, scale_b=l1_scale_b,
        expert_offsets=expert_offsets,
        global_scale_a=global_scale_a, global_scale_b=l1_gs,
    )

    # Apply SiLU in PyTorch (reference)
    silu_ref = torch.nn.functional.silu(out_bf16)

    print(f"L1 BF16 output shape: {out_bf16.shape}")
    print(f"SiLU reference shape: {silu_ref.shape}")
    print(f"L1 output amax: {out_bf16.abs().amax().item():.4f}")
    print(f"SiLU reference amax: {silu_ref.abs().amax().item():.4f}")
    print()
    print("Step 1 validation: SiLU in PyTorch on BF16 GEMM output")
    print("Next step: Run fused kernel with SiLU in registers and compare")
    print()
    print("NOTE: The fused kernel with SiLU on the full acc_vec should produce")
    print("the same result as torch.nn.functional.silu on the BF16 output,")
    print("within NVFP4 quantization tolerance (~5e-2).")
    print()
    print("This test validates the SiLU math. The gate/up pairing (Step 2)")
    print("will change which values get SiLU applied (gate only, not up).")


if __name__ == "__main__":
    test_silu_in_registers()
