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appendix: update dis example to reflect code changes in main text
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‎learners/technical-appendix.md‎

Lines changed: 93 additions & 90 deletions
Original file line numberDiff line numberDiff line change
@@ -14,13 +14,18 @@ The topics covered here exceed the level of knowledge required to benefit from t
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You can use `dis` to view the bytecode generated by Python. The amount of bytecode more strongly correlates with how much code is being executed by the Python interpreter and hence how long it may take to execute. However, this is a crude proxy as it does not account for functions that are called and whether those functions are implemented using Python or C.
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The pure Python search compiles to 82 lines of bytecode.
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The pure Python search compiles to 51 lines of bytecode. (Note that different versions of Python may produce slightly different bytecode than shown here.)
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```python
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import dis
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import random
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# Generate sample data
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N = 2500
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M = 2
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ls = [random.randint(0, int(N*M)) for i in range(N)]
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def manualSearch():
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ls = generateInputs()
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ct = 0
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for i in range(0, int(N*M), M):
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for j in range(0, len(ls)):
@@ -31,65 +36,63 @@ def manualSearch():
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dis.dis(manualSearch)
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```
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```output
34-
11 0 LOAD_GLOBAL 0 (generateInputs)
35-
2 CALL_FUNCTION 0
36-
4 STORE_FAST 0 (ls)
37-
38-
12 6 LOAD_CONST 1 (0)
39-
8 STORE_FAST 1 (ct)
40-
41-
13 10 LOAD_GLOBAL 1 (range)
42-
12 LOAD_CONST 1 (0)
43-
14 LOAD_GLOBAL 2 (int)
44-
16 LOAD_GLOBAL 3 (N)
45-
18 LOAD_GLOBAL 4 (M)
46-
20 BINARY_MULTIPLY
47-
22 CALL_FUNCTION 1
48-
24 LOAD_GLOBAL 4 (M)
49-
26 CALL_FUNCTION 3
50-
28 GET_ITER
51-
>> 30 FOR_ITER 24 (to 80)
52-
32 STORE_FAST 2 (i)
53-
54-
14 34 LOAD_GLOBAL 1 (range)
55-
36 LOAD_CONST 1 (0)
56-
38 LOAD_GLOBAL 5 (len)
57-
40 LOAD_FAST 0 (ls)
58-
42 CALL_FUNCTION 1
59-
44 CALL_FUNCTION 2
60-
46 GET_ITER
61-
>> 48 FOR_ITER 14 (to 78)
62-
50 STORE_FAST 3 (j)
63-
64-
15 52 LOAD_FAST 0 (ls)
65-
54 LOAD_FAST 3 (j)
66-
56 BINARY_SUBSCR
67-
58 LOAD_FAST 2 (i)
68-
60 COMPARE_OP 2 (==)
69-
62 POP_JUMP_IF_FALSE 38 (to 76)
70-
71-
16 64 LOAD_FAST 1 (ct)
72-
66 LOAD_CONST 2 (1)
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68 INPLACE_ADD
74-
70 STORE_FAST 1 (ct)
75-
76-
17 72 POP_TOP
77-
74 JUMP_FORWARD 1 (to 78)
78-
79-
15 >> 76 JUMP_ABSOLUTE 24 (to 48)
80-
>> 78 JUMP_ABSOLUTE 15 (to 30)
81-
82-
13 >> 80 LOAD_CONST 0 (None)
83-
82 RETURN_VALUE
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9 RESUME 0
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10 LOAD_CONST 1 (0)
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STORE_FAST 0 (ct)
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11 LOAD_GLOBAL 1 (range + NULL)
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LOAD_CONST 1 (0)
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LOAD_GLOBAL 3 (int + NULL)
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LOAD_GLOBAL 4 (N)
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LOAD_GLOBAL 6 (M)
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BINARY_OP 5 (*)
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CALL 1
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LOAD_GLOBAL 6 (M)
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CALL 3
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GET_ITER
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L1: FOR_ITER 56 (to L5)
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STORE_FAST 1 (i)
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12 LOAD_GLOBAL 1 (range + NULL)
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LOAD_CONST 1 (0)
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LOAD_GLOBAL 9 (len + NULL)
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LOAD_GLOBAL 10 (ls)
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CALL 1
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CALL 2
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GET_ITER
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L2: FOR_ITER 24 (to L4)
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STORE_FAST 2 (j)
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13 LOAD_GLOBAL 10 (ls)
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LOAD_FAST 2 (j)
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BINARY_SUBSCR
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LOAD_FAST 1 (i)
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COMPARE_OP 88 (bool(==))
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POP_JUMP_IF_TRUE 2 (to L3)
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JUMP_BACKWARD 18 (to L2)
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14 L3: LOAD_FAST 0 (ct)
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LOAD_CONST 2 (1)
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BINARY_OP 13 (+=)
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STORE_FAST 0 (ct)
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15 POP_TOP
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JUMP_BACKWARD 54 (to L1)
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12 L4: END_FOR
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POP_TOP
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JUMP_BACKWARD 58 (to L1)
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11 L5: END_FOR
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POP_TOP
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RETURN_CONST 0 (None)
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```
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Whereas the `in` variant only compiles to 54.
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Whereas the `in` variant only compiles to 33.
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```python
89-
import dis
90-
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def operatorSearch():
92-
ls = generateInputs()
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ct = 0
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for i in range(0, int(N*M), M):
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if i in ls:
@@ -98,43 +101,43 @@ def operatorSearch():
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dis.dis(operatorSearch)
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```
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```output
101-
4 0 LOAD_GLOBAL 0 (generateInputs)
102-
2 CALL_FUNCTION 0
103-
4 STORE_FAST 0 (ls)
104-
105-
5 6 LOAD_CONST 1 (0)
106-
8 STORE_FAST 1 (ct)
107-
108-
6 10 LOAD_GLOBAL 1 (range)
109-
12 LOAD_CONST 1 (0)
110-
14 LOAD_GLOBAL 2 (int)
111-
16 LOAD_GLOBAL 3 (N)
112-
18 LOAD_GLOBAL 4 (M)
113-
20 BINARY_MULTIPLY
114-
22 CALL_FUNCTION 1
115-
24 LOAD_GLOBAL 4 (M)
116-
26 CALL_FUNCTION 3
117-
28 GET_ITER
118-
>> 30 FOR_ITER 10 (to 52)
119-
32 STORE_FAST 2 (i)
120-
121-
7 34 LOAD_FAST 2 (i)
122-
36 LOAD_FAST 0 (ls)
123-
38 CONTAINS_OP 0
124-
40 POP_JUMP_IF_FALSE 25 (to 50)
125-
126-
8 42 LOAD_FAST 1 (ct)
127-
44 LOAD_CONST 2 (1)
128-
46 INPLACE_ADD
129-
48 STORE_FAST 1 (ct)
130-
>> 50 JUMP_ABSOLUTE 15 (to 30)
131-
132-
6 >> 52 LOAD_CONST 0 (None)
133-
54 RETURN_VALUE
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1 RESUME 0
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106+
2 LOAD_CONST 1 (0)
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STORE_FAST 0 (ct)
108+
109+
3 LOAD_GLOBAL 1 (range + NULL)
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LOAD_CONST 1 (0)
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LOAD_GLOBAL 3 (int + NULL)
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LOAD_GLOBAL 4 (N)
113+
LOAD_GLOBAL 6 (M)
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BINARY_OP 5 (*)
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CALL 1
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LOAD_GLOBAL 6 (M)
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CALL 3
118+
GET_ITER
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L1: FOR_ITER 20 (to L3)
120+
STORE_FAST 1 (i)
121+
122+
4 LOAD_FAST 1 (i)
123+
LOAD_GLOBAL 8 (ls)
124+
CONTAINS_OP 0
125+
POP_JUMP_IF_TRUE 2 (to L2)
126+
JUMP_BACKWARD 15 (to L1)
127+
128+
5 L2: LOAD_FAST 0 (ct)
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LOAD_CONST 2 (1)
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BINARY_OP 13 (+=)
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STORE_FAST 0 (ct)
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JUMP_BACKWARD 22 (to L1)
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3 L3: END_FOR
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POP_TOP
136+
RETURN_CONST 0 (None)
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```
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A naive assessment of how expensive two functions are can be carried out with this comparison.
137-
However this method of displaying bytecode only shows bytecode for the requested function, so it is not clear how expensive called function's will be or higher level changes to an algorithm which could reduce the number of iterations or similar.
140+
However this method of displaying bytecode only shows bytecode for the requested function, so it is not clear how expensive called functions will be or higher level changes to an algorithm which could reduce the number of iterations or similar.
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## Hardware Level Memory Accesses
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