Disk caching?

[Richard Frost]

Code: QB64: [Select]

1. 'In getting to know _MEMCOPY I wrote this test to see what speed improvement I'd get by preloading all
2. 'data and moving it around vs. loading each file as needed.  Suprisingly, there's not much difference.
3. 'Is it disk caching that negates the "improvement"?
4.  
5. 'Where I do find _MEMCOPY indispensible is in shifting all elements of an array down one element, which
6. 'isn't part of this test code.
7.  
8. DEFINT A-Z
9. GOSUB init
10. DO
11.     GOSUB way_new
12.     GOSUB way_old
13. LOOP
14.  
15. init:
16. z = 20000
17. DIM a0(z), a1(z), a2(z), a3(z), a4(z), a5(z)
18. DIM amem(6) AS _MEM
19. amem(0) = _MEM(a0()): amem(1) = _MEM(a1()): amem(2) = _MEM(a2())
20. amem(3) = _MEM(a3()): amem(4) = _MEM(a4()): amem(5) = _MEM(a5())
21. FOR i = 1 TO 5
22.     f$ = "h" + LTRIM$(STR$(i)) + ".dat"
23.     s& = VARSEG(a0(0))
24.     o& = VARPTR(a0(0))
25.     DEF SEG = s&
26.     BLOAD f$, o&
27.     _MEMCOPY amem(0), amem(0).OFFSET, amem(0).SIZE TO amem(i), amem(i).OFFSET
28. NEXT i
29. SCREEN 9
30. z$ = "010249042456075632380052085407"
31. FOR i = 0 TO 14
32.     PALETTE i + 1, VAL(MID$(z$, i * 2 + 1, 2))
33. NEXT i
34. RETURN
35.  
36. way_new:
37. t! = TIMER
38. FOR t = 0 TO 4
39.     FOR j = 0 TO 12
40.         k = j * 1500
41.         FOR i = 1 TO 5
42.             _MEMCOPY amem(i), amem(i).OFFSET, amem(i).SIZE TO amem(0), amem(0).OFFSET
43.             y = (i - 1) * 70
44.             PUT (0, y), a0(k), PSET
45.             LINE (46, y)-(90, y + 70), 0, BF
46.             LINE (0, y)-(90, y + 13), 0, BF
47.         NEXT i
48.         _DISPLAY
49.         _DELAY .04
50.     NEXT j
51.     IF LEN(INKEY$) THEN END
52. NEXT t
53. LOCATE 2, 30: PRINT "new ";: PRINT USING "##.####"; TIMER - t!;
54. RETURN
55.  
56. way_old:
57. t! = TIMER
58. FOR t = 0 TO 4
59.     FOR j = 0 TO 12
60.         k = j * 1500
61.         FOR i = 1 TO 5
62.             f$ = "h" + LTRIM$(STR$(i)) + ".dat"
63.             s& = VARSEG(a0(0))
64.             o& = VARPTR(a0(0))
65.             DEF SEG = s&
66.             BLOAD f$, o&
67.             y = (i - 1) * 70
68.             PUT (100, y), a0(k), PSET
69.             LINE (146, y)-(190, y + 70), 0, BF
70.             LINE (100, y)-(190, y + 13), 0, BF
71.         NEXT i
72.         _DISPLAY
73.         _DELAY .04
74.     NEXT j
75.     IF LEN(INKEY$) THEN END
76. NEXT t
77. LOCATE 3, 30: PRINT "old ";: PRINT USING "##.####"; TIMER - t!;
78. RETURN
79.