Breaking or continue from nested loop
lazarus / 61-Beginners

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Flaze07 · 2018-06-08 14:09

I need to break or continue from nested loop, I found a thread on it
before, http://forum.lazarus.freepascal.org/index.php?topic=30867.0 it
suggest breaking into function or procedure. Well I am using the code
for https://www.codechef.com/problems/SUBINC and so I need it to be
fast. ( I used Dlang before pascal, and my code was too slow ), so is
using flag or goto better ? or maybe breaking it into function or
procedure don't have that much overhead ?

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Handoko · 2018-06-08 14:21

Please show us your code, we may able to help you optimize it.

Programmers usually avoid using goto nowadays, because improper use of
it can make the code hard to debug and maintain.

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Flaze07 · 2018-06-08 14:30

well...I am not that done with the code.
oh well, I am going to show two codes, Dlang and Pascal
https://www.codechef.com/viewsolution/18828694 ( this is the Dlang )
https://gist.github.com/Flaze07/2d544f82b2f06c5f91e6410e8b27e4ad (
this is Pascal, I managed to somewhat convert it, but it is still not
correct )

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Flaze07 · 2018-06-08 15:03

I managed to convert it good, but it turned out to be slower than
Dlang counterpart https://www.codechef.com/viewsolution/18831781 oh
well, time to try it out with good ol' C++, or maybe there's something
in the pascal version that is slowing the whole thing down ?

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marcov · 2018-06-08 15:10

This is a multi level exit (or, GOTO) problem. The code exists the
inner-for, but also aborts the outer-for body skipping the nascending
statement.

FPC has no multilevel exit except "exit' that exits a whole procedure.
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 procedure
doinner;begin  for inner ...      begin          if something then   
       exit        end;nAscending:=nAscending+1;end; begin  for
outer:=....          doinner;end;
Or you could try with goto.

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Flaze07 · 2018-06-08 15:14

well, in the end I used flag...not sure if that is good, goto seems
like a good approach too though, I don't know if I want to consider
using procedure as using just one function that I made seems to make
the Pascal program slower than Dlang's version of the same program

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marcov · 2018-06-08 15:22

Don't forget to flag it as inline, and configure the compiler (lazarus
menus or cmdline) to inline

As why it is slower, if you translate foreign concepts into a
different language, there is a chance that it is not the best option
for that language.

It might also be unrelated parts (like stdio being slower by default,
or memory management being more conservative, thus growing arrays in
small increments is slower).

Benchmarking is an art. Once we had a fairly major issue with a large
scale FPC user saying the code was slower than Kylix/Delphi. Turned
out to be that differences in the speed of random() used in the tests
that created the main difference, not the algorithm/codegeneration.
(FPC has a higher quality but slower random)

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Flaze07 · 2018-06-08 15:27

yeah, I suppose you are right, might try what you suggested. Also, I
am not that good with figuring out new ways of doing things, but then
again, I don't really expect the pascal code to be faster than the
Dlang code, I expect to be about as fast

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Thaddy · 2018-06-08 15:29

The procedural approach is achievable when using inlined functions
that return a boolean instead of a procedure. Depending on the boolean
return value you can do further breaks/continue on higher levels.
Another (or combined) approach is to use local procedures or functions
(with e.g. an assignable typed constant in the main block). You can
achieve the same effect.
But technically that is also flag.

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Flaze07 · 2018-06-08 15:37

ok, thank you for all the help, it's been helpful

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ASerge · 2018-06-09 12:17

Quote from: Flaze07 on June 08, 2018, 04:30:40 pmwell...I am not that
done with the code.
oh well, I am going to show two codes, Dlang and Pascal
https://www.codechef.com/viewsolution/18828694 ( this is the Dlang )
https://gist.github.com/Flaze07/2d544f82b2f06c5f91e6410e8b27e4ad (
this is Pascal, I managed to somewhat convert it, but it is still not
correct )
1. Code in Dlang  contains error:
Code: C  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i secondOuter
: for( int j = i + 1; j <= arrLength; ++j ); // must be < allLength2.
There is no need to copy each time to a separate array for
verification. It is better to do it on it, just pointing out from and
to.
3. In the main question I agree with Thaddy - it is better to use a
separate function, you can mark it as inline.
4. And most importantly: your solves the problem WRONG! Index j should
start from i, not from i +1.
Work sample:
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 program
Project1;{$APPTYPE CONSOLE}{$MODE OBJFPC} type  TArray = array of
Cardinal; function IsAscending(const A: TArray; AFrom, ATo: Integer):
Boolean;var  i: Integer;begin  for i := AFrom + 1 to ATo do    if A[i
- 1] > A[i] then      Exit(False);  Result := True;end; function
ReadArray(out A: TArray): Boolean;var  ArrLength, i: Integer;begin 
Readln(ArrLength);  if ArrLength <= 0 then    Exit(False); 
SetLength(A, ArrLength);  for i := Low(A) to High(A) do   
Read(A[i]);  Readln; // Skip end of line  Result :=
True;end; procedure DoTest;var  i, j: Integer;  Arr: TArray; 
CountOfAscendings: Integer;begin  if not ReadArray(Arr) then  begin  
Writeln('Bad array length');    Exit;  end;  CountOfAscendings := 0; 
for i := Low(Arr) to High(Arr) do  begin    for j := i to High(Arr)
do      if IsAscending(Arr, i, j) then        Inc(CountOfAscendings); 
end;  Writeln(CountOfAscendings);end; var  TestsCount: Cardinal;begin 
Readln(TestsCount);  while TestsCount > 0 do  begin    DoTest;   
Dec(TestsCount);  end;  Readln;end.

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Thaddy · 2018-06-09 12:24

@ASerge
It is always nice to see compilable examples.... compliments.