所以我正在为课堂编写ARM程序集quicksort方法。除了复杂性没有意义之外，我在很大程度上理解了这一点。
我们将它与我们制作的另一个冒泡排序方法进行比较，并且对于具有1个参数和10个参数的示例，它表现更好。然而，我甚至无法比较100参数测试，因为它需要太长时间......我不能让它甚至做到75，但是在几秒钟内完成了50次。
这就是我所拥有的，
qsort: @ Takes three parameters:
@ a: Pointer to base of array a to be sorted (arrives in r0)
@ n: number of elements in the array (arrives in r1)
stmfd sp!, {r4, r6, lr} @ Save r4 and r6 for caller
mov r6, r1 @ r6 <- right
mov r2, #0 @ r2 <- left
qsort_tailcall_entry:
sub r7, r6, r2 @ If right - left <= 1 (already sorted),
cmp r7, #1
ldmlefd sp!, {r4, r6, pc} @ Return, restoring r4 and r6
ldr r7, [r0, r2, asl #2] @ r7 <- a[left], gets pivot element
add r1, r2, #1 @ l <- left + 1
mov r4, r6 @ r <- right
partition_loop:
ldr r3, [r0, r1, asl #2] @ r3 <- a[l]
cmp r3, r7 @ If a[l] <= pivot_element,
addle r1, r1, #1 @ ... increment l, and
ble partition_test @ ... continue to next iteration.
sub r4, r4, #1 @ Otherwise, decrement r,
ldr r8, [r0, r4, asl #2] @ ... and swap a[l] and a[r].
str r8, [r0, r1, asl #2]
str r3, [r0, r4, asl #2]
partition_test:
cmp r1, r4 @ If l < r,
blt partition_loop @ ... continue iterating.
partition_finish:
sub r1, r1, #1 @ Decrement l
ldr r3, [r0, r1, asl #2] @ Swap a[l] and pivot
str r3, [r0, r2, asl #2]
str r7, [r0, r1, asl #2]
bl qsort @ Call self recursively on left part,
@ with args a (r0), left (r2), r (r2),
@ also preserves r4 and r6
mov r2, r4
b qsort_tailcall_entry @ Tail-call self on right part,
@ with args a (r0), l (r2), right (r6)
任何人都可以帮助我理解为什么世界上它长期以来呈指数增长吗？我该怎么做才能解决它？
答案 0 :(得分：0)
我没有研究过您的逻辑，但已经为您的程序添加了一些可能对您有帮助的调试脚本。包装器是一个独立的程序。
/* qsort1.s */
@ ---- Added ----
.data
tstdat:
.word 9, 9, 9, 9, 9
array:
.word 3, 7, 8, 5, 2, 1, 9, 5, 4
len:
.word ((len - array) /4)
.balign 4
format:
.asciz " %2d %2d %2d %2d %2d %2d %2d %2d %2d | %2d %2d %2d\n"
.text
.global main
Print:
push {r0-v7, lr}
mrs v7, cpsr
push {v7, v8}
push {r2, r6, r7}
ldr r7, =array
ldm r7, {r1-r9}
push {r4-r9}
ldr r0, =format
bl printf
add sp, #36
pop {v7, v8}
msr cpsr_f, v7
pop {r0-v7, pc}
main:
ldr r0, =array
ldr r1, =len
ldr r1, [r1]
push {r3-r11, lr}
bl Print
bl qsort
bl Print
pop {r3-r11, pc}
@ ---------------------------
qsort: @ Takes three parameters:
@ a: Pointer to base of array a to be sorted (arrives in r0)
@ n: number of elements in the array (arrives in r1)
stmfd sp!, {r4, r6, lr} @ Save r4 and r6 for caller
mov r6, r1 @ r6 <- right
mov r2, #0 @ r2 <- left
qsort_tailcall_entry:
sub r7, r6, r2 @ If right - left <= 1 (already sorted),
@ bl Print @ <---- Added
cmp r7, #1
ldmlefd sp!, {r4, r6, pc} @ Return, restoring r4 and r6
ldr r7, [r0, r2, asl #2] @ r7 <- a[left], gets pivot element
add r1, r2, #1 @ l <- left + 1
mov r4, r6 @ r <- right
partition_loop:
ldr r3, [r0, r1, asl #2] @ r3 <- a[l]
cmp r3, r7 @ If a[l] <= pivot_element,
addle r1, r1, #1 @ ... increment l, and
ble partition_test @ ... continue to next iteration.
sub r4, r4, #1 @ Otherwise, decrement r,
ldr r8, [r0, r4, asl #2] @ ... and swap a[l] and a[r].
str r8, [r0, r1, asl #2]
str r3, [r0, r4, asl #2]
bl Print @ <---- Added
partition_test:
cmp r1, r4 @ If l < r,
blt partition_loop @ ... continue iterating.
partition_finish:
sub r1, r1, #1 @ Decrement l
ldr r3, [r0, r1, asl #2] @ Swap a[l] and pivot
str r3, [r0, r2, asl #2]
str r7, [r0, r1, asl #2]
bl qsort @ Call self recursively on left part,
@ with args a (r0), left (r2), r (r2),
@ also preserves r4 and r6
mov r2, r4
b qsort_tailcall_entry @ Tail-call self on right part,
@ with args a (r0), l (r2), right (r6)
这是输出的开始。左侧是要排序的数组，右侧是r2，r6和r7。此数组来自https://en.wikipedia.org/wiki/Quicksort（https://upload.wikimedia.org/wikipedia/commons/a/af/Quicksort-diagram.svg）。
pi@RPi:~/pgm $ mym qsort1
as -o qsort1.o qsort1.s
gcc -o qsort1 qsort1.o
./qsort1; echo $?
3 7 8 5 2 1 9 5 4 | 2126935836 66296 0 (before pgm)
3 4 8 5 2 1 9 5 7 | 0 9 3
3 5 8 5 2 1 9 4 7 | 0 9 3
3 9 8 5 2 1 5 4 7 | 0 9 3
3 1 8 5 2 9 5 4 7 | 0 9 3
3 1 2 5 8 9 5 4 7 | 0 9 3
...
( array to be sorted ) r2 r4 r7
答案 1 :(得分：0)
要修复quicksort以获得更长时间，修复方法是使用＆＃39; Linux qsort＆＃39;排序数字。
@ http://www.tutorialspoint.com/c_standard_library/c_function_qsort.htm
@
@ http://man7.org/linux/man-pages/man3/qsort.3.html
@
@ void qsort(void *base, size_t nmemb, size_t size,
@ int (*compar)(const void *, const void *));
@
@ qsort(r0 =array, r1 =numelements, r2 = 4 bytes,
@ r0=(r3 =cmpfunc){ r0=[r0] - r1=[r1] })
cmpfunc:
ldr r0, [r0]
ldr r1, [r1]
sub r0, r0, r1
mov pc, lr
qsort_setup:
ldr r0, =array
ldr r1, =numbytes
lsr r1, #2
mov r2, #4
ldr r3, =cmpfunc
bl qsort
使用随机数的完整演示程序。
/* qsort14.s */
.data
@ See /usr/include/arm-linux-gnueabihf/asm/unistd.h
@ See /usr/include/arm-linux-gnueabihf/bits/fcntl-linux.h
.equ create, 8
.equ Mode, 0644 @ -rw-r--r--
.equ open, 5
.equ Rd, 00
.equ Wr, 01
.equ RdWr, 02
.equ Apnd, 02000
.equ read, 3
.equ write, 4
.equ close, 6
.equ sync, 36
.equ exit, 1
.equ sfile, 187
.equ numbytes, (64 * 4) @ Has to be multiples
@ .equ numbytes, (128 * 4) @ of 8 times 4.
@ .equ numbytes, (512 * 4)
.balign 4
array: .skip numbytes
.balign 4
dir_file:
.asciz "/dev/urandom"
.balign 4
Open:
.word dir_file, RdWr | Apnd, open
.balign 4
Read:
.word array, numbytes, read
.balign 4
hex3ff:
.word 0x3ff
.balign 4
format:
.asciz " %4u %4u %4u %4u %4u %4u %4u %4u\n"
.balign 4
fmt:
.asciz "\n"
@ ---------------------------
.text
.global main
Prt_arr:
push {r0-r12, lr}
mrs r12, cpsr
push {r11, r12}
mov r0, #0xa
bl putchar
ldr r12, =numbytes
lsr r12, #5
mov r11, #0
endprt:
ldr r0, =array
add r0, r11
ldm r0, {r1-r8}
push {r4-r12}
ldr r0, =format
bl printf
pop {r4-r12}
add r11, #32
subs r12, #1
bne endprt
pop {r11, r12}
msr cpsr_f, r12
pop {r0-r12, lr}
mov pc, lr
@ ---- Program starts here ----
@ ---- Read random numbers ----
main:
push {r4-r12, lr}
ldr r3, =Open @ load address
ldm r3, {r0, r1, r7} @ load registers
svc #0 @ OS opens urandom file
mov r4, r0 @ save fd in r4
ldr r3, =Read @ load address
ldm r3, {r1, r2, r7} @ load registers
svc #0 @ OS reads urandom file
mov r0, r4 @ move fd in r0
mov r7, #close @ num for close
svc #0 @ OS closes urandom file
@ ---- Fix array so numbers are 999 or less ----
ldr r10, =array
ldr r1, =numbytes
sub r1, #4
ldr r2, =hex3ff
ldr r2, [r2]
fix:
ldr r0, [r10, r1]
and r0, r2
cmp r0, #1000
subge r0, #1000
lslge r0, r0, #5
str r0, [r10, r1]
subs r1, #4
bpl fix
@ ---- Print unsorted array ----
bl Prt_arr
b qsort_setup
@ http://www.tutorialspoint.com/c_standard_library/c_function_qsort.htm
@
@ http://man7.org/linux/man-pages/man3/qsort.3.html
@
@ void qsort(void *base, size_t nmemb, size_t size,
@ int (*compar)(const void *, const void *));
@
@ qsort(r0 =array, r1 =numelements, r2 = 4 bytes,
@ r0=(r3 =cmpfunc){ r0=[r0] - r1=[r1] })
cmpfunc:
ldr r0, [r0]
ldr r1, [r1]
sub r0, r0, r1
mov pc, lr
qsort_setup:
ldr r0, =array
ldr r1, =numbytes
lsr r1, #2
mov r2, #4
ldr r3, =cmpfunc
bl qsort
End:
bl Prt_arr
mov r0, #0xa
bl putchar
pop {r4-r12, lr}
bx lr
.end