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rubidium

(svn r17776) -Codechange: [SDL] make "update the video card"-process asynchronious. Profiling with gprof etc. hasn't shown us that DrawSurfaceToScreen takes a significant amount of CPU; only using TIC/TOC it became apparant that it was a heavy CPU-cycle user or that it was waiting for something.
The benefit of making this function asynchronious ranges from 2%-25% (real time) during fast forward on dual core/hyperthreading-enabled CPUs; 8bpp improvements are, in my test cases, significantly smaller than 32bpp improvements.
On single core non-hyperthreading-enabled CPUs the extra locking/scheduling costs up to 1% extra realtime in fast forward. You can use -v sdl:no_threads to disable threading and undo this loss.
During normal non-fast-forwarded games the benefit/costs are negligable except when the gameloop takes more than about 90% of the time of a tick.
Note that allegro's performance does not improve with this system, likely due to their way of getting data to the video card. It is not implemented for the OS X/Windows video backends, unless (ofcourse) SDL is used there.
Funny is that the performance of the 32bpp(-anim) blitter is, at least in some test cases, significantly faster (more than 10%) than the 8bpp(-optimized) blitter when looking at real time in fast forward on a dual core CPU; it was slower.
The idea comes from a paper/report by Idar Borlaug and Knut Imar Hagen.

/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file date_type.h Types related to the dates in OpenTTD. */

#ifndef DATE_TYPE_H
#define DATE_TYPE_H

/**
 * 1 day is 74 ticks; _date_fract used to be uint16 and incremented by 885. On
 *                    an overflow the new day begun and 65535 / 885 = 74.
 * 1 tick is approximately 30 ms.
 * 1 day is thus about 2 seconds (74 * 30 = 2220) on a machine that can run OpenTTD normally
 */
enum {
	DAY_TICKS = 74,          ///< ticks per day
	DAYS_IN_YEAR = 365,      ///< days per year
	DAYS_IN_LEAP_YEAR = 366, ///< sometimes, you need one day more...
};

/*
 * ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR and DAYS_TILL_ORIGINAL_BASE_YEAR are
 * primarily used for loading newgrf and savegame data and returning some
 * newgrf (callback) functions that were in the original (TTD) inherited
 * format, where '_date == 0' meant that it was 1920-01-01.
 */

/** The minimum starting year/base year of the original TTD */
#define ORIGINAL_BASE_YEAR 1920
/** The original ending year */
#define ORIGINAL_END_YEAR 2051
/** The maximum year of the original TTD */
#define ORIGINAL_MAX_YEAR 2090

/**
 * The offset in days from the '_date == 0' till
 * 'ConvertYMDToDate(ORIGINAL_BASE_YEAR, 0, 1)'
 */
#define DAYS_TILL_ORIGINAL_BASE_YEAR (DAYS_IN_YEAR * ORIGINAL_BASE_YEAR + ORIGINAL_BASE_YEAR / 4 - ORIGINAL_BASE_YEAR / 100 + ORIGINAL_BASE_YEAR / 400)

/* The absolute minimum & maximum years in OTTD */
#define MIN_YEAR 0
/* MAX_YEAR, nicely rounded value of the number of years that can
 * be encoded in a single 32 bits date, about 2^31 / 366 years. */
#define MAX_YEAR 5000000

typedef int32  Date;
typedef uint16 DateFract;

typedef int32  Year;
typedef uint8  Month;
typedef uint8  Day;

/**
 * Data structure to convert between Date and triplet (year, month, and day).
 * @see ConvertDateToYMD(), ConvertYMDToDate()
 */
struct YearMonthDay {
	Year  year;   ///< Year (0...)
	Month month;  ///< Month (0..11)
	Day   day;    ///< Day (1..31)
};

static const Year INVALID_YEAR = -1;
static const Date INVALID_DATE = -1;

#endif /* DATE_TYPE_H */