[Common] Extract Functions to Get and Validate Group Sizes in Weights Compression

src/nncf/quantization/algorithms/weight_compression/algorithm.py

@@ -70,6 +70,32 @@
     TensorDataType.f8e4m3,
     TensorDataType.f8e5m2,
 ]
+FIXED_GROUP_SIZE_MODES = {
+    CompressWeightsMode.MXFP4: 32,
+    CompressWeightsMode.MXFP8_E4M3: 32,
+    CompressWeightsMode.NVFP4: 16,
+}
+PER_CHANNEL_BY_DEFAULT_MODES = [
+    *INT8_MODES,
+    CompressWeightsMode.CODEBOOK,
+    CompressWeightsMode.CB4,
+    CompressWeightsMode.ADAPTIVE_CODEBOOK,
+]
+DEFAULT_GROUP_SIZE_FOR_NON_INT8_MODES = 128
+
+
+def get_default_group_size(mode: CompressWeightsMode) -> int:
+    """
+    Returns the group size to use for the given mode when no group size is requested explicitly.
+
+    :param mode: Compression mode to get the default group size for.
+    :return: Default group size for the given mode.
+    """
+    if mode in FIXED_GROUP_SIZE_MODES:
+        return FIXED_GROUP_SIZE_MODES[mode]
+    if mode in PER_CHANNEL_BY_DEFAULT_MODES:
+        return -1
+    return DEFAULT_GROUP_SIZE_FOR_NON_INT8_MODES
 
 
 def get_weight_compression_configuration(
@@ -90,22 +116,8 @@ def get_weight_compression_configuration(
     """
     Generates a configuration dictionary for weight compression based on the provided parameters.
     """
-    if group_size is None and mode in INT8_MODES:
-        group_size = -1
-    elif group_size is None and mode in NON_INT8_MODES:
-        if mode in [CompressWeightsMode.MXFP4, CompressWeightsMode.MXFP8_E4M3]:
-            group_size = 32
-        elif mode == CompressWeightsMode.NVFP4:
-            group_size = 16
-        elif mode in [
-            CompressWeightsMode.CODEBOOK,
-            CompressWeightsMode.CB4,
-            CompressWeightsMode.ADAPTIVE_CODEBOOK,
-        ]:
-            group_size = -1
-        else:
-            group_size = 128
-
+    if group_size is None:
+        group_size = get_default_group_size(mode)
     if backup_mode is None:
         if mode in [CompressWeightsMode.MXFP4, CompressWeightsMode.MXFP8_E4M3]:
             backup_mode = BackupMode.MXFP8_E4M3
@@ -138,6 +150,33 @@ def get_weight_compression_configuration(
     }
 
 
+def validate_fixed_group_size(
+    mode: CompressWeightsMode, group_size: int | None, advanced_parameters: AdvancedCompressionParameters | None = None
+) -> None:
+    """
+    Validates the group size requested for a mode which accepts only specific group sizes.
+
+    :param mode: Compression mode to validate.
+    :param group_size: Group size requested for the given mode. None means that the default value is used.
+    :param advanced_parameters: Advanced compression parameters that may affect the validation.
+    """
+    fixed_group_size = FIXED_GROUP_SIZE_MODES.get(mode)
+    if fixed_group_size is not None and group_size not in [None, fixed_group_size]:
+        msg = f"{mode.value} type only supports group size of {fixed_group_size}, group size of {group_size} is given"
+        raise nncf.ValidationError(msg)
+    if (
+        fixed_group_size is not None
+        and advanced_parameters
+        and advanced_parameters.group_size_fallback_mode is GroupSizeFallbackMode.ADJUST
+    ):
+        msg = (
+            f"{mode.value} type only supports group size of {fixed_group_size}, so it does not support the group size"
+            f" fallback mode {advanced_parameters.group_size_fallback_mode.value}."
+            " Please use other group size fallback mode."
+        )
+        raise nncf.ValidationError(msg)
+
+
 def check_user_compression_configuration(
     mode: CompressWeightsMode,
     subset_size: int,
@@ -278,22 +317,7 @@ def check_user_compression_configuration(
             f"Supported modes are: {[e.value for e in GroupSizeFallbackMode]}."
         )
         raise nncf.ValidationError(msg)
-    if mode in [CompressWeightsMode.MXFP4, CompressWeightsMode.MXFP8_E4M3, CompressWeightsMode.NVFP4]:
-        if mode in [CompressWeightsMode.MXFP4, CompressWeightsMode.MXFP8_E4M3] and group_size not in [None, 32]:
-            msg = f"MXFP4 and MXFP8_E4M3 types only support group size of 32, group size of {group_size} is given"
-            raise nncf.ValidationError(msg)
-
-        if mode == CompressWeightsMode.NVFP4 and group_size not in [None, 16]:
-            msg = f"NVFP4 type only supports group size of 16, group size of {group_size} is given"
-            raise nncf.ValidationError(msg)
-
-        if advanced_parameters and advanced_parameters.group_size_fallback_mode is GroupSizeFallbackMode.ADJUST:
-            msg = (
-                "MXFP4, MXFP8_E4M3 and NVFP4 types do not support the group size"
-                f" fallback mode {advanced_parameters.group_size_fallback_mode.value}."
-                " Please use other group size fallback mode."
-            )
-            raise nncf.ValidationError(msg)
+    validate_fixed_group_size(mode, group_size, advanced_parameters)
 
 
 class WeightCompression(Algorithm):