[Quantization] MSE-calibrate every per-expert weight in fused-experts MoE

modelopt/torch/export/moe_utils.py

@@ -110,11 +110,19 @@ def _export_fused_experts(module: nn.Module, dtype: torch.dtype) -> None:
                 and w_quantizer._amax.dim() >= 1
             ):
                 amax = w_quantizer._amax
+                # Per-block _amax (NVFP4 static) collapses the row axis we want
+                # to slice on; restore it so dim-0 slicing splits gate/up.
+                if amax.numel() != fused_total and amax.numel() % fused_total == 0:
+                    amax = amax.contiguous().view(fused_total, amax.numel() // fused_total)
                 amax_dim0 = amax.shape[0]
                 if fused_total % amax_dim0 == 0:
                     slice_start = fused_start * amax_dim0 // fused_total
                     slice_end = (fused_start + weight_slice.shape[0]) * amax_dim0 // fused_total
-                    w_quantizer.amax = amax[slice_start:slice_end].contiguous()
+                    sliced = amax[slice_start:slice_end].contiguous()
+                    # The amax setter refuses shape changes; drop _amax first.
+                    if hasattr(w_quantizer, "_amax"):
+                        delattr(w_quantizer, "_amax")
+                    w_quantizer.amax = sliced
                 else:
                     warnings.warn(
                         f"Expert {idx} {proj_name}: fused amax dim0 ({amax_dim0}) does not "

modelopt/torch/export/unified_export_hf.py

@@ -1134,6 +1134,19 @@ def _unpatch_revert_weight_conversion(patches: list[tuple[Any, Any]]) -> None:
         mod.revert_weight_conversion = original
 
 
+def _sanitize_generation_config_for_save(model: torch.nn.Module) -> None:
+    """Force ``do_sample=True`` when generation_config has ``top_k``/``top_p`` set.
+
+    Newer transformers reject ``do_sample=False`` mixed with sampling attrs in
+    ``save_pretrained``'s strict validate.
+    """
+    gc = getattr(model, "generation_config", None)
+    if gc is None:
+        return
+    if getattr(gc, "top_k", None) is not None or getattr(gc, "top_p", None) is not None:
+        gc.do_sample = True
+
+
 def export_speculative_decoding(
     model: torch.nn.Module,
     dtype: torch.dtype | None = None,
@@ -1228,6 +1241,8 @@ def export_hf_checkpoint(
         # modeling_utils does `from core_model_loading import revert_weight_conversion`.
         _patches = _patch_revert_weight_conversion()
 
+        _sanitize_generation_config_for_save(model)
+
         try:
             model.save_pretrained(
                 export_dir,

modelopt/torch/quantization/model_calib.py

@@ -52,7 +52,6 @@
     promote_nvfp4_static_quantizers,
     quantizer_attr_names,
     reduce_amax,
-    weight_attr_names,
 )
 from .utils.calib_utils import _GPTQ_HELPER_REGISTRY, GPTQHelper
 
@@ -64,8 +63,100 @@
     "max_calibrate",
     "smoothquant",
     "svdquant",
+    "sync_grouped_weight_global_amax",
 ]
 
+
+# Sibling groups that share an FP8 scale-of-scales: members feed the same input
+# (Q/K/V) or get fused at deployment (gate/up), so divergent global_amax would
+# split their FP8 grids.
+_GROUPED_WEIGHT_QUANTIZER_PATTERNS: tuple[tuple[str, ...], ...] = (
+    ("q_proj", "k_proj", "v_proj"),
+    ("gate_proj", "up_proj"),  # Llama/Qwen/Mistral
+    ("w1", "w3"),  # Mixtral
+)
+
+
+def _collect_grouped_linears(model: nn.Module) -> list[list[nn.Module]]:
+    """Collect sibling groups (Q/K/V, gate/up) with calibrated NVFP4-static weight quantizers."""
+    groups: list[list[nn.Module]] = []
+    wq_attr = quantizer_attr_names("weight").weight_quantizer
+    for parent in model.modules():
+        for sibling_names in _GROUPED_WEIGHT_QUANTIZER_PATTERNS:
+            members = []
+            for n in sibling_names:
+                child = getattr(parent, n, None)
+                wq = getattr(child, wq_attr, None) if child is not None else None
+                if (
+                    isinstance(wq, TensorQuantizer)
+                    and not wq._disabled
+                    and wq.is_nvfp4_static
+                    and getattr(wq, "_amax", None) is not None
+                ):
+                    members.append(child)
+            if len(members) >= 2:
+                groups.append(members)
+    return groups
+
+
+@torch.no_grad()
+def _bootstrap_uncalibrated_weight_quantizers(model: nn.Module) -> int:
+    """Populate ``_amax`` from weights for quantizers the forward pass didn't reach.
+
+    Dead MoE experts that received no tokens are otherwise skipped by
+    ``mse_calibrate``, leaving export to derive separate per-half amax for
+    gate/up and break the gate==up ``weight_scale_2`` invariant.
+    """
+    n = 0
+    for module in model.modules():
+        if not isinstance(module, QuantModule):
+            continue
+        for weight, q in module.iter_weights_for_calibration():
+            if not isinstance(q, TensorQuantizer) or q._disabled or q._dynamic:
+                continue
+            if q._calibrator is None:
+                continue
+            if getattr(q, "_amax", None) is not None and not torch.all(q._amax == 0):
+                continue
+            q.disable_quant()
+            q.enable_calib()
+            q(weight)
+            if q._calibrator.compute_amax() is not None:
+                q.load_calib_amax()
+            q.enable_quant()
+            q.disable_calib()
+            if hasattr(q._calibrator, "reset"):
+                q._calibrator.reset()
+            n += 1
+    return n
+
+
+@torch.no_grad()
+def sync_grouped_weight_global_amax(model: nn.Module) -> int:
+    """Unify NVFP4 ``global_amax`` across Q/K/V and gate/up sibling weight quantizers.
+
+    Reuses ``preprocess_linear_fusion`` (which performs the same unification at
+    export time) to keep the FP8 scale-of-scales consistent across siblings
+    during MSE / local-Hessian search. Must run after ``max_calibrate``.
+    """
+    # Inline: quant_utils imports enable_stats_collection/finish_stats_collection/svd
+    # from this module, so top-level would deadlock the cycle.
+    from modelopt.torch.export.quant_utils import preprocess_linear_fusion
+
+    wq_attr = quantizer_attr_names("weight").weight_quantizer
+    n_groups = 0
+    for group in _collect_grouped_linears(model):
+        for child in group:
+            wq = getattr(child, wq_attr)
+            if not isinstance(wq, NVFP4StaticQuantizer):
+                NVFP4StaticQuantizer.from_tensor_quantizer(
+                    wq, global_amax=reduce_amax(wq._amax, axis=None)
+                )
+        preprocess_linear_fusion(group)
+        n_groups += 1
+    return n_groups
+
+
 CalibratorFactory: TypeAlias = Callable[
     [torch.Tensor, int | tuple | list | None, Callable[..., torch.Tensor]], _Calibrator
 ]
@@ -346,32 +437,25 @@ def mse_calibrate(
     See :class:`MseCalibConfig <modelopt.torch.quantization.config.MseCalibConfig>` for
     details on the remaining arguments.
     """
-    # Step 1: First get initial amax using max calibration
+    # Step 1: max calibration; then populate _amax for dead experts so step 3
+    # doesn't skip them, and unify NVFP4 global_amax across Q/K/V and gate/up
+    # siblings so MSE searches against a consistent FP8 grid.
     max_calibrate(model, forward_loop, distributed_sync)
+    _bootstrap_uncalibrated_weight_quantizers(model)
+    sync_grouped_weight_global_amax(model)
 
-    # Step 2: Replace calibrators with MseCalibrator for enabled quantizers
-    # and identify weight quantizers
-    weight_quantizers = []
-    seen_modules = set()
-
+    # Step 2: replace calibrators with MseCalibrator for enabled quantizers.
     for name, module in list(model.named_modules()):
         if isinstance(module, TensorQuantizer) and not module._disabled:
             if module._calibrator is not None and not module._dynamic and hasattr(module, "_amax"):
-                # Get the initial amax from max calibration
                 initial_amax = module._amax.clone().detach()
+                is_nvfp4_static = module.is_nvfp4_static
 
-                is_nvfp4_static = (
-                    module.is_static_block_quant
-                    and module._num_bits == (2, 1)
-                    and module._block_sizes is not None
-                    and module._block_sizes.get("scale_bits") == (4, 3)
-                )
-
-                if is_nvfp4_static:
-                    # Compute and set global_amax
+                # sync_grouped_weight_global_amax may have already promoted +
+                # unified global_amax across the sibling group; only promote
+                # standalone (non-grouped) NVFP4-static quantizers here.
+                if is_nvfp4_static and not isinstance(module, NVFP4StaticQuantizer):
                     global_amax = reduce_amax(initial_amax, axis=None)
-
-                    # Convert to NVFP4StaticQuantizer in-place
                     NVFP4StaticQuantizer.from_tensor_quantizer(module, global_amax=global_amax)
 
                 if fp8_scale_sweep:
@@ -412,52 +496,50 @@ def mse_calibrate(
                     quant_func=partial(_mse_quant_func, quantizer=module),
                 )
 
-    # Identify weight quantizers by checking if they have corresponding weight parameters
+    # Step 3: calibrate weight quantizers via iter_weights_for_calibration.
+    # The fused-experts override yields one pair per expert per projection, so
+    # every per-expert quantizer is MSE-calibrated (not just routed ones).
     name_to_module = dict(model.named_modules())
+    seen_modules: set[int] = set()
+    pbar = tqdm(desc="MSE weight calibration")
+    n_calibrated = 0
     for parent_module in name_to_module.values():
-        if parent_module in seen_modules:
+        if id(parent_module) in seen_modules or not isinstance(parent_module, QuantModule):
             continue
-        for weight_name in weight_attr_names(parent_module):
-            weight_quantizer_name = quantizer_attr_names(weight_name).weight_quantizer
-            weight_quantizer = getattr(parent_module, weight_quantizer_name, None)
-            if isinstance(weight_quantizer, TensorQuantizer) and weight_quantizer.is_enabled:
-                if getattr(weight_quantizer, "_calibrator", None) is not None:
-                    weight_quantizers.append((parent_module, weight_name, weight_quantizer))
-        seen_modules.add(parent_module)
-
-    # Step 3: Calibrate weight quantizers ONE AT A TIME with immediate amax computation
-    # This prevents massive memory accumulation seen in large models
-    for idx, (parent_module, weight_name, weight_quantizer) in enumerate(
-        tqdm(weight_quantizers, desc="MSE weight calibration")
-    ):
-        # Enable calibration mode for the weight quantizer
-        weight_quantizer.disable_quant()
-        weight_quantizer.enable_calib()
+        seen_modules.add(id(parent_module))
         with enable_weight_access_and_writeback(parent_module, model, name_to_module):
-            weight = getattr(parent_module, weight_name)
-            weight_quantizer(weight)
+            for weight, weight_quantizer in parent_module.iter_weights_for_calibration():
+                if not (
+                    isinstance(weight_quantizer, TensorQuantizer)
+                    and weight_quantizer.is_enabled
+                    and getattr(weight_quantizer, "_calibrator", None) is not None
+                ):
+                    continue
+                weight_quantizer.disable_quant()
+                weight_quantizer.enable_calib()
+                weight_quantizer(weight)
 
-        # IMMEDIATELY compute amax and reset calibrator to free memory
-        cal = getattr(weight_quantizer, "_calibrator", None)
-        if cal is not None and cal.compute_amax() is not None:
-            weight_quantizer.load_calib_amax()
+                cal = weight_quantizer._calibrator
+                if cal.compute_amax() is not None:
+                    weight_quantizer.load_calib_amax()
 
-        weight_quantizer.enable_quant()
-        weight_quantizer.disable_calib()
+                weight_quantizer.enable_quant()
+                weight_quantizer.disable_calib()
 
-        # Synchronize ALL CUDA devices before resetting to ensure all async operations complete
-        # This is critical for multi-GPU setups where tensors may be on different devices
-        if torch.cuda.is_available():
-            for dev_id in range(torch.cuda.device_count()):
-                torch.cuda.synchronize(torch.device(f"cuda:{dev_id}"))
+                if torch.cuda.is_available():
+                    for dev_id in range(torch.cuda.device_count()):
+                        torch.cuda.synchronize(torch.device(f"cuda:{dev_id}"))
 
-        if cal is not None and hasattr(cal, "reset"):
-            cal.reset()
+                if hasattr(cal, "reset"):
+                    cal.reset()
 
-        if (idx + 1) % 10 == 0 and torch.cuda.is_available():
-            for dev_id in range(torch.cuda.device_count()):
-                torch.cuda.synchronize(torch.device(f"cuda:{dev_id}"))
-            torch.cuda.empty_cache()
+                pbar.update(1)
+                n_calibrated += 1
+                if n_calibrated % 10 == 0 and torch.cuda.is_available():
+                    for dev_id in range(torch.cuda.device_count()):
+                        torch.cuda.synchronize(torch.device(f"cuda:{dev_id}"))
+                    torch.cuda.empty_cache()
+    pbar.close()
 
     if torch.cuda.is_available():
         for dev_id in range(torch.cuda.device_count()):
@@ -612,6 +694,8 @@ def forward(self, input, *args, **kwargs):
     print_rank_0("local_hessian: Running max calibration for all quantizers...")
     max_calibrate(model, forward_loop, distributed_sync)
 
+    sync_grouped_weight_global_amax(model)
+
     # Setup helpers for all quantized linear modules
     name_to_module = dict(model.named_modules())
     weight_quantizers_info = []
@@ -666,14 +750,9 @@ def quant_func(x, amax, quantizer=weight_quantizer):
 
             return xq
 
-        is_nvfp4_static = (
-            weight_quantizer.is_static_block_quant
-            and weight_quantizer._num_bits == (2, 1)
-            and weight_quantizer._block_sizes is not None
-            and weight_quantizer._block_sizes.get("scale_bits") == (4, 3)
-        )
+        is_nvfp4_static = weight_quantizer.is_nvfp4_static
 
-        if is_nvfp4_static:
+        if is_nvfp4_static and not isinstance(weight_quantizer, NVFP4StaticQuantizer):
             global_amax = reduce_amax(initial_amax, axis=None)
             NVFP4StaticQuantizer.from_tensor_quantizer(weight_quantizer, global_amax=global_amax)
 

modelopt/torch/quantization/nn/modules/tensor_quantizer.py

@@ -514,6 +514,16 @@ def is_mx_format(self):
             and self.block_sizes.get("scale_bits", None) == (8, 0)
         )
 
+    @property
+    def is_nvfp4_static(self):
+        """True for E2M1 weights + E4M3 per-block scales in static layout (format-only check)."""
+        return (
+            self.is_static_block_quant
+            and self._num_bits == (2, 1)
+            and self._block_sizes is not None
+            and self._block_sizes.get("scale_bits") == (4, 3)
+        )
+
     def is_mxfp(self, bits):
         """Check if is MXFP4/MXFP6/MXFP8."""
         if bits == 4:

modelopt/torch/quantization/plugins/huggingface.py

@@ -900,6 +900,24 @@ def forward(self, *args, **kwargs):
         self._down_proj_linear = False
         return super().forward(*args, **kwargs)
 
+    def iter_weights_for_calibration(self):
+        """Yield ``(weight_slice, quantizer)`` per-expert pairs.
+
+        The base impl uses singular ``*_weight_quantizer`` and skips fused-
+        experts modules, so weight-only calibration never reaches per-expert
+        quantizers without this override.
+        """
+        for weight_name, quantizers_name in (
+            ("gate_up_proj", "gate_up_proj_weight_quantizers"),
+            ("down_proj", "down_proj_weight_quantizers"),
+        ):
+            weight = getattr(self, weight_name, None)
+            quantizers = getattr(self, quantizers_name, None)
+            if weight is None or quantizers is None:
+                continue
+            for idx, q in enumerate(quantizers):
+                yield weight[idx], q
+
     def fold_weight(self, keep_attrs: bool = False):
         """Fold per-expert weight quantizers into the fused 3-D weights.
 

modelopt/torch/quantization/utils/core_utils.py

@@ -957,13 +957,7 @@ def promote_nvfp4_static_quantizers(model: nn.Module) -> int:
     for _name, module in list(model.named_modules()):
         if isinstance(module, TensorQuantizer) and not module._disabled:
             if module._calibrator is not None and not module._dynamic and hasattr(module, "_amax"):
-                is_nvfp4_static = (
-                    module.is_static_block_quant
-                    and module._num_bits == (2, 1)
-                    and module._block_sizes is not None
-                    and module._block_sizes.get("scale_bits") == (4, 3)
-                )
-                if is_nvfp4_static:
+                if module.is_nvfp4_static:
                     initial_amax = module._amax.clone().detach()
                     global_amax = reduce_amax(initial_amax, axis=None)
                     NVFP4StaticQuantizer.from_tensor_quantizer(module, global_amax=global_amax)