optimization will generate wrong result
lazarus / 62-General

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powerpcer · 2021-05-11 16:26

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][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   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][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i j:=edit_dis
tance_bit('agtcaaaagtcagtcagtcagtcagtcacagtcagaaggcatccaaccga','ccgtta
gtcagaaacagtcagtcagtcagtcagtccagtcttaggcccgga');

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AlexTP · 2021-05-11 16:31

FPC 3.2 fixes; Linux x64.

-O0: 14
-O1: 14
-O2: 16

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bytebites · 2021-05-11 16:42

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
fillbyte(Peq,0,sizeof(Peq));
Your code is wrong. The second argument of fillchar is count, the last
is value.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i Pv :=Pv or
(ONE shl i);
Pv is not initialised.

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powerpcer · 2021-05-12 01:13

thanks,
after fixed, -O3 optimize faster little, from 40ms to 30ms