fix plot filter for v2 plots

Author: arvidn

chia/_tests/core/custom_types/test_proof_of_space.py

@@ -291,10 +291,10 @@ def test_calculate_prefix_bits_v1(height: uint32, expected: int) -> None:
     argvalues=[
         (0, 5),
         (0xFFFFFFFA, 5),
-        (0xFFFFFFFB, 6),
-        (0xFFFFFFFC, 7),
-        (0xFFFFFFFD, 8),
-        (0xFFFFFFFF, 8),
+        (0xFFFFFFFB, 4),
+        (0xFFFFFFFC, 3),
+        (0xFFFFFFFD, 2),
+        (0xFFFFFFFF, 2),
     ],
 )
 def test_calculate_prefix_bits_v2(height: uint32, expected: int) -> None:

chia/types/blockchain_format/proof_of_space.py

@@ -211,13 +211,14 @@ def passes_plot_filter(
 
 def calculate_prefix_bits(constants: ConsensusConstants, height: uint32, plot_param: PlotParam) -> int:
     if plot_param.strength_v2 is not None:
+        prefix_bits = int(constants.NUMBER_ZERO_BITS_PLOT_FILTER_V2)
         if height >= constants.PLOT_FILTER_V2_THIRD_ADJUSTMENT_HEIGHT:
-            return constants.NUMBER_ZERO_BITS_PLOT_FILTER_V2 + 3
-        if height >= constants.PLOT_FILTER_V2_SECOND_ADJUSTMENT_HEIGHT:
-            return constants.NUMBER_ZERO_BITS_PLOT_FILTER_V2 + 2
-        if height >= constants.PLOT_FILTER_V2_FIRST_ADJUSTMENT_HEIGHT:
-            return constants.NUMBER_ZERO_BITS_PLOT_FILTER_V2 + 1
-        return constants.NUMBER_ZERO_BITS_PLOT_FILTER_V2
+            prefix_bits -= 3
+        elif height >= constants.PLOT_FILTER_V2_SECOND_ADJUSTMENT_HEIGHT:
+            prefix_bits -= 2
+        elif height >= constants.PLOT_FILTER_V2_FIRST_ADJUSTMENT_HEIGHT:
+            prefix_bits -= 1
+        return max(0, prefix_bits)
 
     prefix_bits = int(constants.NUMBER_ZERO_BITS_PLOT_FILTER_V1)
     if height >= constants.PLOT_FILTER_32_HEIGHT: