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optimization will generate wrong result
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Topic: optimization will generate wrong result (Read 1125 times)
powerpcer
Full Member
Posts: 100
optimization will generate wrong result
«
on:
May 11, 2021, 06:26:08 pm »
for function below, if i change the optimization to -O2, the result will be wrong 11, the correct one is 18.
i test this code on win10 x64
Code: Pascal
[Select]
[+]
[-]
function
edit_distance_bit
(
str1
,
str2
:
string
)
:
integer
;
var
Peq
:
array
[
0
..
255
]
of
Uint64
;
Pv
,
Eq
,
Xv
,
Xh
,
Ph
,
Mh
,
Mv
,
ONE
:
Uint64
;
i
,
j
,
m
,
n
,
Score
:
integer
;
p1
,
p2
:
pbyte
;
s
:
string
;
begin
if
(
length
(
str1
)
< length
(
str2
)
)
then
begin
p1
:
=
@
str2
[
1
]
;
p2
:
=
@
str1
[
1
]
;
m
:
=
length
(
str2
)
;
n
:
=
length
(
str1
)
;
end
else
begin
p1
:
=
@
str1
[
1
]
;
p2
:
=
@
str2
[
1
]
;
m
:
=
length
(
str1
)
;
n
:
=
length
(
str2
)
;
end
;
ONE
:
=
1
;
fillbyte
(
Peq
,
0
,
sizeof
(
Peq
)
)
;
Mv
:
=
0
;
Score
:
=
m
;
for
i
:
=
0
to
m
do
begin
Peq
[
p1
[
i
]
]
:
=
Peq
[
p1
[
i
]
]
or
ONE
shl
i
;
Pv
:
=
Pv
or
(
ONE
shl
i
)
;
end
;
for
j
:
=
0
to
n
do
begin
Eq
:
=
Peq
[
p2
[
j
]
]
;
Xv
:
=
Eq
or
Mv
;
Xh
:
=
(
(
(
Eq
and
Pv
)
+
Pv
)
xor
Pv
)
or
Eq
;
Ph
:
=
Mv
or
(
not
(
Xh
or
Pv
)
)
;
Mh
:
=
Pv
and
Xh
;
if
(
Ph
and
(
ONE
shl
(
m
-
1
)
)
)
<>
0
then
inc
(
Score
)
else
if
(
Mh
and
(
ONE
shl
(
m
-
1
)
)
)
<>
0
then
dec
(
Score
)
;
Ph
:
=
Ph
shl
ONE
;
Pv
:
=
(
Mh
shl
ONE
)
or
(
not
(
Xv
or
Ph
)
)
;
Mv
:
=
Ph
and
Xv
;
end
;
result
:
=
Score
;
end
;
with testing code
Code: Pascal
[Select]
[+]
[-]
j
:
=
edit_distance_bit
(
'agtcaaaagtcagtcagtcagtcagtcacagtcagaaggcatccaaccga'
,
'ccgttagtcagaaacagtcagtcagtcagtcagtccagtcttaggcccgga'
)
;
Logged
AlexTP
Hero Member
Posts: 2365
Re: optimization will generate wrong result
«
Reply #1 on:
May 11, 2021, 06:31:05 pm »
FPC 3.2 fixes; Linux x64.
-O0: 14
-O1: 14
-O2: 16
Logged
CudaText editor
-
ATSynEdit
-
More from me
bytebites
Hero Member
Posts: 624
Re: optimization will generate wrong result
«
Reply #2 on:
May 11, 2021, 06:42:33 pm »
Code: Pascal
[Select]
[+]
[-]
fillbyte
(
Peq
,
0
,
sizeof
(
Peq
)
)
;
Your code is wrong. The second argument of fillchar is count, the last is value.
Code: Pascal
[Select]
[+]
[-]
Pv
:
=
Pv
or
(
ONE
shl
i
)
;
Pv is not initialised.
Logged
powerpcer
Full Member
Posts: 100
Re: optimization will generate wrong result
«
Reply #3 on:
May 12, 2021, 03:13:23 am »
thanks,
after fixed, -O3 optimize faster little, from 40ms to 30ms
«
Last Edit: May 12, 2021, 03:18:01 am by powerpcer
»
Logged
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optimization will generate wrong result
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