simplfy and remove zscore

src/axolotl/core/builders/causal.py

@@ -320,10 +320,6 @@ class HFCausalTrainerBuilder(TrainerBuilderBase):
             training_arguments_kwargs["kd_alpha"] = self.cfg.kd_alpha
         if self.cfg.kd_temperature is not None:
             training_arguments_kwargs["kd_temperature"] = self.cfg.kd_temperature
-        if self.cfg.kd_zscore_base_temp is not None:
-            training_arguments_kwargs["kd_zscore_base_temp"] = (
-                self.cfg.kd_zscore_base_temp
-            )
 
         if self.cfg.reward_model:
             training_args_cls = AxolotlRewardConfig

src/axolotl/core/training_args.py

@@ -194,13 +194,6 @@ class AxolotlTrainingMixins:
         },
     )
 
-    kd_zscore_base_temp: Optional[float] = field(
-        default=None,
-        metadata={
-            "help": "the base temperature parameter for KL divergence with z-score when using KD"
-        },
-    )
-
     adam_beta3: Optional[float] = field(
         default=None,
         metadata={

src/axolotl/integrations/kd/args.py

@@ -31,4 +31,3 @@ class KDArgs(BaseModel):
     )
     kd_alpha: Optional[float] = None  # loss coefficient for KD loss
     kd_temperature: Optional[float] = None  # temperature for sampling during KD
-    kd_zscore_base_temp: Optional[float] = None  # base temperature for zscore scaling

src/axolotl/integrations/kd/topk_logprob/forward_kl.py

@@ -19,40 +19,6 @@ import torch
 from torch import nn
 
 
-def zscore_standardize(
-    logits: torch.Tensor,
-    mask: torch.Tensor = None,
-    base_temperature: float = 1.0,
-    eps: float = 1e-9,
-):
-    """
-    Z-score standardize along the last dimension of `logits`.
-    i.e., for each [B, seq_len] row, across K entries:
-        z = (logits - mean) / std,
-    then scale by 1 / base_temperature if desired.
-
-    mask can be broadcastable or None. If None, we standardize all elements.
-    """
-    if mask is None:
-        # shape: [B, seq_len, K]
-        # Mean and std over dim=-1
-        mean = logits.mean(dim=-1, keepdim=True)
-        var = logits.var(dim=-1, unbiased=False, keepdim=True)
-    else:
-        # If you have to exclude some tokens, multiply by mask, etc.
-        float_mask = mask.to(logits.dtype)
-        count = float_mask.sum(dim=-1, keepdim=True).clamp_min(1.0)
-        mean = (logits * float_mask).sum(dim=-1, keepdim=True) / count
-        var = (float_mask * (logits - mean) ** 2).sum(dim=-1, keepdim=True) / count
-
-    std = torch.sqrt(var.clamp_min(eps))
-    z = (logits - mean) / std
-
-    # Scale by 1 / base_temperature
-    z = z / base_temperature
-    return z
-
-
 @torch.jit.script
 def loss(
     student_logits: torch.Tensor,
@@ -134,85 +100,6 @@ def loss(
     return kd_loss
 
 
-def topk_kd_loss_with_zscore(
-    student_logits: torch.Tensor,  # [B, seq_len, vocab_size]
-    target_token_ids: torch.Tensor,  # [B, seq_len, K]
-    target_logprobs: torch.Tensor,  # [B, seq_len, K], sums to 1.0 in prob space
-    target_mask: torch.Tensor,  # [B, seq_len, K] or [B, seq_len]
-    kd_temperature: float = 1.0,  # classic KD temperature
-    zscore_base_temp: float = 1.0,  # from the paper
-    num_items_in_batch: int = -1,
-):
-    """
-    A variant of top_k KL divergence with Z-score scaling
-    from "Logit Standardization in Knowledge Distillation".
-    """
-
-    target_logprobs = target_logprobs.float()
-
-    B, teacher_seq_len, K = target_logprobs.shape  # pylint: disable=invalid-name
-    # 1) Gather the student's top-k logits to match teacher
-    student_logits_for_kd = student_logits[
-        :, :teacher_seq_len, :
-    ]  # [B, seq_len, vocab]
-    student_topk_logits = torch.gather(
-        student_logits_for_kd, dim=-1, index=target_token_ids
-    )  # [B, seq_len, K]
-
-    student_topk_logits = student_topk_logits.float()
-
-    # 2) If you want to keep the "classical" T scaling, apply it first
-    if kd_temperature != 1.0:
-        student_topk_logits = student_topk_logits / kd_temperature
-
-    # 3) Convert teacher logprobs -> treat them as “logits” for z-score
-    #    (They differ by +some_constant from real logits, but in z-score
-    #     that constant is subtracted out anyway.)
-    teacher_logits_for_zscore = target_logprobs  # rename variable for clarity
-
-    # 4) Z-score teacher and student
-    #    If target_mask is 2D, expand to 3D for the K dimension
-    if target_mask.dim() == 2 and target_mask.shape[:2] == (B, teacher_seq_len):
-        target_mask = target_mask.unsqueeze(-1).expand(-1, -1, K)
-
-    teacher_z = zscore_standardize(
-        teacher_logits_for_zscore, mask=target_mask, base_temperature=zscore_base_temp
-    )
-    student_z = zscore_standardize(
-        student_topk_logits, mask=target_mask, base_temperature=zscore_base_temp
-    )
-
-    # 5) Convert to log-probs for KL
-    teacher_logprobs_z = teacher_z - torch.logsumexp(teacher_z, dim=-1, keepdim=True)
-    student_logprobs_z = student_z - torch.logsumexp(student_z, dim=-1, keepdim=True)
-
-    # 6) Restrict to valid tokens if needed
-    valid_mask = target_mask.bool()  # shape [B, seq_len, K]
-    teacher_probs_z = teacher_logprobs_z.exp()
-    teacher_probs_z = teacher_probs_z[valid_mask]
-    teacher_logprobs_z = teacher_logprobs_z[valid_mask]
-    student_logprobs_z = student_logprobs_z[valid_mask]
-
-    # 7) forward KL:  sum( p_teacher * [log(p_teacher) - log(p_student)] )
-    kd_loss_per_token = teacher_probs_z * (teacher_logprobs_z - student_logprobs_z)
-    kd_loss = kd_loss_per_token.sum()
-
-    # 8) If using classical KD scaling by T^2
-    if kd_temperature != 1.0:
-        kd_loss = kd_loss * (kd_temperature**2)
-
-    # Optionally scale by zscore_base_temp**2 if you want (paper might differ).
-    # kd_loss = kd_loss * (zscore_base_temp**2)
-
-    # 9) Normalize
-    if num_items_in_batch is not None and num_items_in_batch > 0:
-        kd_loss = kd_loss / float(num_items_in_batch)
-    else:
-        kd_loss = kd_loss / float(kd_loss_per_token.size(0))
-
-    return kd_loss
-
-
 class ChunkedTopKKDLoss(nn.Module):
     """
     A wrapper that chunks (splits) the student and teacher outputs along the time dimension

src/axolotl/integrations/kd/trainer.py

@@ -18,7 +18,7 @@ KD trainer
 
 from axolotl.core.trainers.base import AxolotlTrainer
 
-from .topk_logprob.forward_kl import ChunkedTopKKDLoss, topk_kd_loss_with_zscore
+from .topk_logprob.forward_kl import ChunkedTopKKDLoss
 
 
 class AxolotlKDTrainer(AxolotlTrainer):
@@ -80,24 +80,13 @@ class AxolotlKDTrainer(AxolotlTrainer):
         target_token_ids_for_loss = target_token_ids[..., 1:, :].contiguous()
         target_mask_for_loss = target_mask[..., 1:, :].contiguous()
 
-        if self.args.kd_zscore_base_temp:
-            loss_kd = topk_kd_loss_with_zscore(
-                shift_logits,
-                target_token_ids_for_loss,
-                target_logprobs_for_loss,
-                target_mask_for_loss,
-                kd_temperature=self.args.kd_temperature,
-                zscore_base_temp=self.args.kd_zscore_base_temp,
-                num_items_in_batch=num_items_in_batch,
-            )
-        else:
-            loss_kd = self.kd_loss_fn(
-                shift_logits,
-                target_token_ids_for_loss,
-                target_logprobs_for_loss,
-                target_mask_for_loss,
-                num_items_in_batch=num_items_in_batch,
-            )
+        loss_kd = self.kd_loss_fn(
+            shift_logits,
+            target_token_ids_for_loss,
+            target_logprobs_for_loss,
+            target_mask_for_loss,
+            num_items_in_batch=num_items_in_batch,
+        )
 
         if self.args.kd_ce_alpha > 0:
             kd_alpha = self.args.kd_alpha