Change HPU warmup logic: seq length should be with exponential growth (#3217)

Signed-off-by: Liu, Kaixuan <kaixuan.liu@intel.com>
Co-authored-by: regisss <15324346+regisss@users.noreply.github.com>

Author: kaixuanliu

backends/gaudi/server/text_generation_server/models/causal_lm.py

@@ -56,6 +56,7 @@
 CHUNK_SIZES = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048]
 LAZY_MODE = int(os.environ.get("PT_HPU_LAZY_MODE", 1))
 BATCH_SIZE_EXPONENT_BASE = int(os.environ.get("BATCH_SIZE_EXPONENT_BASE", 2))
+SEQ_LEN_EXPONENT_BASE = int(os.environ.get("SEQ_LEN_EXPONENT_BASE", 2))
 MAX_BATCH_SIZE = (
     int(os.environ.get("MAX_BATCH_SIZE"))
     if os.environ.get("MAX_BATCH_SIZE") is not None
@@ -71,8 +72,21 @@ def torch_compile_for_eager(func):
     )
 
 
-def round_up_seq(number, k):
-    return (number + k - 1) // k * k
+def round_up_seq(number, k, base):
+    exponent = math.ceil(math.log(number / k, base))
+    return int(k * (base**exponent))
+
+
+def iterate_powers_of_base(max_value, start, base):
+    current = start
+    result = []
+    assert (
+        max_value >= start
+    ), f"max_value {max_value} must be greater than start {start}"
+    while current < max_value:
+        result.append(current)
+        current *= base
+    return result
 
 
 def round_up_batch(number):
@@ -575,7 +589,9 @@ def from_pb(
             assert (
                 PAD_SEQUENCE_TO_MULTIPLE_OF <= max_input_length
             ), "PAD_SEQUENCE_TO_MULTIPLE_OF cannot be higher than max_input_length"
-            rounded_seq_len = round_up_seq(input_len + 1, PAD_SEQUENCE_TO_MULTIPLE_OF)
+            rounded_seq_len = round_up_seq(
+                input_len + 1, PAD_SEQUENCE_TO_MULTIPLE_OF, SEQ_LEN_EXPONENT_BASE
+            )
             if rounded_seq_len <= max_input_length:
                 bucket_size = rounded_seq_len - 1
             else:
@@ -1345,14 +1361,9 @@ def warmup(
                 max_exp + 1,
             )
         ]
-        prefill_seqlen_list = [
-            seq
-            for seq in range(
-                PAD_SEQUENCE_TO_MULTIPLE_OF,
-                max_input_tokens,
-                PAD_SEQUENCE_TO_MULTIPLE_OF,
-            )
-        ]
+        prefill_seqlen_list = iterate_powers_of_base(
+            max_input_tokens, PAD_SEQUENCE_TO_MULTIPLE_OF, SEQ_LEN_EXPONENT_BASE
+        )
         prefill_seqlen_list.append(max_input_tokens)
         prefill_batch_size_list.sort(reverse=True)
         prefill_seqlen_list.sort(reverse=True)