From d19c768cb80abe48d3763b55cf4602a3b820cbe8 Mon Sep 17 00:00:00 2001
From: Nicolas Patry <patry.nicolas@protonmail.com>
Date: Mon, 19 Feb 2024 15:23:12 +0100
Subject: [PATCH] Fix mistral with length > window_size for long prefills
 (rotary doesn't create long enough cos, sin). (#1571)

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---
 server/text_generation_server/models/flash_mistral.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/server/text_generation_server/models/flash_mistral.py b/server/text_generation_server/models/flash_mistral.py
index 70669c8d..5df4e214 100644
--- a/server/text_generation_server/models/flash_mistral.py
+++ b/server/text_generation_server/models/flash_mistral.py
@@ -460,7 +460,10 @@ class BaseFlashMistral(FlashCausalLM):
             max_s = batch.max_seqlen
             lm_head_indices = batch.prefill_head_indices
 
-        if self.model.max_past is not None:
+        if cu_seqlen_prefill is None and self.model.max_past is not None:
+            # In decode, not prefill, we're actually overwriting the KV-cache
+            # in a circular buffer mode.
+            # This makes sure the max_s for the decode pass is correct.
             max_s = min(self.model.max_past, max_s)
 
         bs = input_ids.shape[0]