Serhiy Storchaka <storchaka+cpyt...@gmail.com> added the comment:
Here is some data. step is the number of items added at a time, the first row
is the size, the second row is the currently allocated size, the third row is
the proposed allocated size.
for step in (1, 2, 3, 4, 5, 6, 7, 8, 9, 10):
sizes0 = range(step, step*31, step)
sizes1 = []
sizes2 = []
old_size = allocated1 = allocated2 = 0
for size in sizes0:
if size > allocated1:
allocated1 = size + (size >> 3) + (3 if size < 9 else 6)
sizes1.append(allocated1)
if size > allocated2:
allocated2 = (size + (size >> 3) + 6) & ~3
if size - old_size > allocated2 - size:
allocated2 = (size + 3) & ~3
sizes2.append(allocated2)
old_size = size
print('\nstep =', step)
print(' '.join(f'{x:3}' for x in sizes0))
print(' '.join(f'{x:3}' for x in sizes1))
print(' '.join(f'{x:3}' for x in sizes2))
step = 1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
4 4 4 4 8 8 8 8 16 16 16 16 16 16 16 16 25 25 25 25
25 25 25 25 25 35 35 35 35 35
4 4 4 4 8 8 8 8 16 16 16 16 16 16 16 16 24 24 24 24
24 24 24 24 32 32 32 32 32 32
step = 2
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
42 44 46 48 50 52 54 56 58 60
5 5 9 9 17 17 17 17 26 26 26 26 26 37 37 37 37 37 48 48
48 48 48 48 62 62 62 62 62 62
8 8 8 8 16 16 16 16 24 24 24 24 32 32 32 32 44 44 44 44
44 44 56 56 56 56 56 56 68 68
step = 3
3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60
63 66 69 72 75 78 81 84 87 90
6 6 16 16 16 26 26 26 36 36 36 36 49 49 49 49 63 63 63 63
63 80 80 80 80 80 97 97 97 97
8 8 16 16 16 24 24 24 36 36 36 36 48 48 48 48 60 60 60 60
76 76 76 76 76 92 92 92 92 92
step = 4
4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80
84 88 92 96 100 104 108 112 116 120
7 12 12 24 24 24 37 37 37 51 51 51 64 64 64 64 82 82 82 82
100 100 100 100 100 123 123 123 123 123
8 8 16 16 28 28 28 40 40 40 52 52 52 68 68 68 68 84 84 84
84 104 104 104 104 104 124 124 124 124
step = 5
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
105 110 115 120 125 130 135 140 145 150
8 17 17 28 28 39 39 51 51 51 67 67 67 84 84 84 101 101 101 101
124 124 124 124 146 146 146 146 146 174
8 16 16 28 28 36 36 48 48 60 60 60 76 76 76 96 96 96 96 116
116 116 116 140 140 140 140 140 168 168
step = 6
6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102 108 114 120
126 132 138 144 150 156 162 168 174 180
9 19 19 33 33 46 46 60 60 60 80 80 80 100 100 100 120 120 120 120
147 147 147 147 174 174 174 174 174 208
12 12 24 24 36 36 52 52 64 64 80 80 80 100 100 100 120 120 120 120
144 144 144 144 172 172 172 172 200 200
step = 7
7 14 21 28 35 42 49 56 63 70 77 84 91 98 105 112 119 126 133 140
147 154 161 168 175 182 189 196 203 210
10 21 21 37 37 53 53 69 69 84 84 84 108 108 108 132 132 132 155 155
155 155 187 187 187 187 218 218 218 218
8 16 28 28 44 44 60 60 76 76 92 92 92 116 116 116 136 136 136 160
160 160 184 184 184 184 216 216 216 216
step = 8
8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 128 136 144 152 160
168 176 184 192 200 208 216 224 232 240
12 24 24 42 42 60 60 78 78 96 96 96 123 123 123 150 150 150 177 177
177 177 213 213 213 213 249 249 249 249
8 24 24 40 40 60 60 76 76 96 96 96 120 120 120 148 148 148 176 176
176 176 212 212 212 212 248 248 248 248
step = 9
9 18 27 36 45 54 63 72 81 90 99 108 117 126 135 144 153 162 171 180
189 198 207 216 225 234 243 252 261 270
16 26 36 36 56 56 76 76 97 97 117 117 117 147 147 147 178 178 178 208
208 208 208 249 249 249 249 289 289 289
12 20 36 36 56 56 76 76 96 96 116 116 136 136 136 168 168 168 196 196
196 228 228 228 228 268 268 268 268 308
step = 10
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
210 220 230 240 250 260 270 280 290 300
17 28 39 51 51 73 73 96 96 118 118 141 141 141 174 174 174 208 208 208
242 242 242 242 287 287 287 287 332 332
12 20 32 40 60 60 84 84 104 104 128 128 152 152 152 184 184 184 216 216
216 252 252 252 252 296 296 296 296 340
----------
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue38373>
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