Time.curTime() bug

cmontiel · 12-20-2012 02:08 AM

Sometimes Time.curTime() gives negative values.

**Esenthel** · 12-22-2012 03:26 PM

Could you please give example of at which code location you can receive negative values?
(like, secondary/main thread? before/after InitPre?)
Can you attach sample code to reproduce the problem?
On what platform are you experiencing this issue? (do other platforms work ok?)

cmontiel · 12-22-2012 03:57 PM

Quote:Could you please give example of at which code location you can receive negative values? (like, secondary/main thread? before/after InitPre?)

Main thread , inside InitPre.

Quote:Can you attach sample code to reproduce the problem?

Code:

MainServer.cpp

#include "stdafx.h"

#include "Server.h"

#include "GameData.h"

void InitPre()

{

    AllocConsole();

    freopen("CONIN$","rb",stdin);

    freopen("CONOUT$","wb",stdout);

    freopen("CONOUT$","wb",stderr);

    App.name("Prison Survival Server");

    App.flag=APP_WORK_IN_BACKGROUND|APP_NO_PAUSE_ON_WINDOW_MOVE_SIZE|APP_NO_FX|​APP_MINIMIZABLE|APP_EXIT_IMMEDIATELY;

    DataPath("Data");

    server.Init();

    while(server.Update()){};

    server.Shutdown();

}

/******************************************************************************/

Bool Init(){return false;}

/******************************************************************************/

void Shut(){}

/******************************************************************************/

Bool Update(){return false;}

/******************************************************************************/

void Draw(){}

Code:

Server.cpp

Bool Server::Update()

{

    deltaTime = Time.curTime() - last_time; 

       //Here deltaTime is negative sometimes due to Time.curTime().

    last_time = Time.curTime();

    // Update Npcs.

    FREPA(ServerNpcs)

    {

        ServerNpcs[i].update();

    }

    // Update NetManager

    netmngr.update();

    return true;

}

Quote:On what platform are you experiencing this issue? (do other platforms work ok?)

Windows 7. I didn't check in other platforms.

**Esenthel** · 12-23-2012 02:07 PM

I've tested following code and could not reproduce the problem

Code:

Flt deltaTime, last_time;

Bool update()

{

   deltaTime = Time.curTime() - last_time; 

   //Here deltaTime is negative sometimes due to Time.curTime().

   if(deltaTime<0)

   {

      int z=0; // it never enters here

   }

   last_time = Time.curTime();

   return true;

}

void InitPre()

{

      while(update()){};

}

Is your last_time value not initialized to zero in constructor of the class?

cmontiel · 12-23-2012 07:01 PM

Yes, deltaTime = 0.f; , last_time = 0.f; in constructor.

I added :

if(deltaTime<0)
{
int z=0; // it never enters here
}

And a breakpoint at int z=0, compiler stops there with deltatime negative value with lots of decimals.

It occurs passed 4 or 5 minutes, sometimes passed 40 minutes. Totally random.

At moment I am using function clock() suggested by SkyKill

Code:

deltaTime = static_cast<double>(clock() - last_time) / CLOCKS_PER_SEC;

last_time = clock();

It seems works well.

**Esenthel** · 12-23-2012 07:35 PM

Time.curTime() most certainly does not have a bug
If you're experiencing this issue, it can be caused by numerical imprecisions, conversions between Dbl and Flt

try using this code:

Code:

Flt delta, last_time;

Bool update()

{

   Flt cur_time=Time.curTime(); // first copy to backup variable

   delta=cur_time-last_time;

   if(delta<0)

   {

      Exit(S+(Dbl)delta+"\n"+(Dbl)cur_time+"\n"+(Dbl)last_time);

   }

   last_time=cur_time; // use cur_time

   return true;

}

if this still won't work, then replace Flt with Dbl for time variables

cmontiel · 12-23-2012 10:57 PM

Quote:Flt cur_time=Time.curTime(); // first copy to backup variable

Solved! That's the key line. Strange because delta and last_time are floats and Time.curTime() returns float too.

**Esenthel** · 12-24-2012 10:53 AM

Cpu's work that way that returned value of a floating point function is always treated as Dbl until it's converted into a Flt variable.
This is because returned values of function are accessed from cpu fpu hw registers which are at least Dbl in precision.

Time.curTime() bug
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