Merge pull request #252 from fvutils/copilot/fix-bin-array-duplicate-values

Fix bin_array to retain duplicate values per IEEE 1800-2023

Author: mballance

.gitignore

@@ -110,3 +110,4 @@ junit/
 
 .venv/
 .venv.bld
+cov.xml

src/vsc/coverage.py

@@ -435,7 +435,11 @@ def __init__(self, nbins, *args):
         if len(args) == 0:
             raise Exception("No bins range specified")
 
-        self.ranges.compact()
+        # NOTE: Do NOT call self.ranges.compact() here!
+        # According to IEEE 1800-2023 (page 585):
+        # "Duplicate values are retained; thus the same value can be assigned to multiple bins"
+        # Calling compact() would merge overlapping ranges and remove duplicates,
+        # which is incorrect for bin distribution.
 
         # Capture the declaration location of this bin
         frame = inspect.stack()[1]

ve/unit/test_bin_array_duplicates.py

@@ -0,0 +1,214 @@
+'''
+Created on 2024
+
+@author: copilot
+
+Test for bin_array duplicate value handling according to IEEE 1800-2023
+'''
+import vsc
+from vsc_test_case import VscTestCase
+
+class TestBinArrayDuplicates(VscTestCase):
+    
+    def test_bin_array_with_duplicates_from_range(self):
+        """Test that duplicate values from a range are properly retained and distributed.
+        
+        According to IEEE 1800-2023 (page 585):
+        "Duplicate values are retained; thus the same value can be assigned to multiple bins"
+        
+        bins fixed [4] = {[1:10], 1, 4, 7} should distribute 13 values as:
+        - Bin 0: 1, 2, 3
+        - Bin 1: 4, 5, 6
+        - Bin 2: 7, 8, 9
+        - Bin 3: 10, 1, 4, 7 (including the duplicates)
+        
+        Note: Values 1, 4, and 7 will hit MULTIPLE bins when sampled (both their range bin
+        and bin 3), which is the correct behavior per the standard.
+        """
+        
+        @vsc.covergroup
+        class my_cg(object):
+            def __init__(self):
+                self.with_sample(dict(a=vsc.uint8_t()))
+                self.a_cp = vsc.coverpoint(
+                    self.a, bins=dict(
+                        fixed=vsc.bin_array([4], [1, 10], 1, 4, 7)
+                    ))
+                
+        cg = my_cg()
+        cg_model = cg.get_model()
+        cp_model = cg_model.coverpoint_l[0]
+        
+        # Should have 4 bins total (distributed from 13 values)
+        self.assertEqual(cp_model.get_n_bins(), 4)
+        
+        # Verify bin structure by checking ranges
+        bin_ranges = []
+        for idx in range(cp_model.get_n_bins()):
+            bin_range = cp_model.get_bin_range(idx)
+            bin_ranges.append(bin_range)
+        
+        # Value 1 should hit multiple bins (bin 0 from range and bin 3 from duplicate)
+        cg.sample(1)
+        self.assertGreater(cp_model.get_bin_hits(0), 0, "Value 1 should hit bin 0")
+        self.assertGreater(cp_model.get_bin_hits(3), 0, "Value 1 should also hit bin 3 (duplicate)")
+        
+        # Value 4 should hit multiple bins
+        cg.sample(4)
+        self.assertGreater(cp_model.get_bin_hits(1), 0, "Value 4 should hit bin 1")
+        self.assertGreater(cp_model.get_bin_hits(3), 0, "Value 4 should also hit bin 3 (duplicate)")
+        
+        # Value 7 should hit multiple bins
+        cg.sample(7)
+        self.assertGreater(cp_model.get_bin_hits(2), 0, "Value 7 should hit bin 2")
+        self.assertGreater(cp_model.get_bin_hits(3), 0, "Value 7 should also hit bin 3 (duplicate)")
+        
+        # Value 10 should only hit bin 3
+        cg.sample(10)
+        self.assertGreater(cp_model.get_bin_hits(3), 0, "Value 10 should hit bin 3")
+        
+        # Value 2 should only hit bin 0 (no duplicate)
+        cg.sample(2)
+        hits_before = cp_model.get_bin_hits(3)
+        cg.sample(2)
+        hits_after = cp_model.get_bin_hits(3)
+        # Bin 3 should not get additional hits from value 2
+        self.assertEqual(hits_before, hits_after, "Value 2 should not hit bin 3")
+        
+    def test_bin_array_with_separate_values(self):
+        """Test that separate values including duplicates are properly distributed.
+        
+        bins fixed [4] = {[4:12], 1, 2, 8} should distribute values as:
+        - Bin 0: 4, 5, 6
+        - Bin 1: 7, 8, 9
+        - Bin 2: 10, 11, 12
+        - Bin 3: 1, 2, 8 (separate values, 8 is also in bin 1)
+        """
+        
+        @vsc.covergroup
+        class my_cg(object):
+            def __init__(self):
+                self.with_sample(dict(a=vsc.uint8_t()))
+                self.a_cp = vsc.coverpoint(
+                    self.a, bins=dict(
+                        fixed=vsc.bin_array([4], [4, 12], 1, 2, 8)
+                    ))
+                
+        cg = my_cg()
+        cg_model = cg.get_model()
+        cp_model = cg_model.coverpoint_l[0]
+        
+        # Should have 4 bins
+        self.assertEqual(cp_model.get_n_bins(), 4)
+        
+        # Verify bin 0: 4, 5, 6
+        cg.sample(4)
+        self.assertGreater(cp_model.get_bin_hits(0), 0)
+        
+        # Verify bin 3 contains the separate values including 8 which is also in bin 1
+        cg.sample(8)
+        self.assertGreater(cp_model.get_bin_hits(1), 0)  # hits bin 1 (from range [4:12])
+        self.assertGreater(cp_model.get_bin_hits(3), 0)  # also hits bin 3 (from separate value 8)
+        
+    def test_bin_array_multiple_single_values(self):
+        """Test distribution of multiple single values without ranges.
+        
+        bins fixed [3] = {1, 2, 3, 4, 5, 6} should distribute as:
+        - Bin 0: 1, 2
+        - Bin 1: 3, 4
+        - Bin 2: 5, 6
+        """
+        
+        @vsc.covergroup
+        class my_cg(object):
+            def __init__(self):
+                self.with_sample(dict(a=vsc.uint8_t()))
+                self.a_cp = vsc.coverpoint(
+                    self.a, bins=dict(
+                        fixed=vsc.bin_array([3], 1, 2, 3, 4, 5, 6)
+                    ))
+                
+        cg = my_cg()
+        cg_model = cg.get_model()
+        cp_model = cg_model.coverpoint_l[0]
+        
+        # Should have 3 bins
+        self.assertEqual(cp_model.get_n_bins(), 3)
+        
+        # Sample each value and verify they hit the correct bins
+        cg.sample(1)
+        self.assertGreater(cp_model.get_bin_hits(0), 0)
+        cg.sample(2)
+        self.assertGreater(cp_model.get_bin_hits(0), 0)
+        
+        cg.sample(3)
+        self.assertGreater(cp_model.get_bin_hits(1), 0)
+        cg.sample(4)
+        self.assertGreater(cp_model.get_bin_hits(1), 0)
+        
+        cg.sample(5)
+        self.assertGreater(cp_model.get_bin_hits(2), 0)
+        cg.sample(6)
+        self.assertGreater(cp_model.get_bin_hits(2), 0)
+        
+    def test_bin_array_exact_duplicate_values(self):
+        """Test that exact duplicate values are retained.
+        
+        bins fixed [2] = {1, 1, 2, 2} should distribute 4 values across 2 bins:
+        - Bin 0: 1, 1
+        - Bin 1: 2, 2
+        """
+        
+        @vsc.covergroup
+        class my_cg(object):
+            def __init__(self):
+                self.with_sample(dict(a=vsc.uint8_t()))
+                self.a_cp = vsc.coverpoint(
+                    self.a, bins=dict(
+                        fixed=vsc.bin_array([2], 1, 1, 2, 2)
+                    ))
+                
+        cg = my_cg()
+        cg_model = cg.get_model()
+        cp_model = cg_model.coverpoint_l[0]
+        
+        # Should have 2 bins
+        self.assertEqual(cp_model.get_n_bins(), 2)
+        
+        # Sample value 1 - should hit both entries in bin 0
+        cg.sample(1)
+        self.assertGreater(cp_model.get_bin_hits(0), 0)
+        
+        # Sample value 2 - should hit both entries in bin 1
+        cg.sample(2)
+        self.assertGreater(cp_model.get_bin_hits(1), 0)
+        
+    def test_bin_array_no_duplicates_simple(self):
+        """Test that the fix doesn't break the simple case without duplicates.
+        
+        bins a1 [4] = {[0:16]} should work as before.
+        """
+        
+        @vsc.covergroup
+        class my_cg(object):
+            def __init__(self):
+                self.with_sample(dict(a=vsc.uint8_t()))
+                self.a_cp = vsc.coverpoint(
+                    self.a, bins=dict(
+                        a1=vsc.bin_array([4], [0, 16])
+                    ))
+                
+        cg = my_cg()
+        cg_model = cg.get_model()
+        cp_model = cg_model.coverpoint_l[0]
+        
+        # Should have 4 bins for 17 values
+        self.assertEqual(cp_model.get_n_bins(), 4)
+        
+        # Test coverage calculation
+        cg.sample(0)
+        cg.sample(3)
+        self.assertEqual(cg.a_cp.get_coverage(), 25)
+        cg.sample(4)
+        cg.sample(7)
+        self.assertEqual(cg.a_cp.get_coverage(), 50)