Archives/OpenTTD-patches
2
0
Fork 0
mirror of https://github.com/JGRennison/OpenTTD-patches.git synced 2024-11-16 00:12:51 +00:00
Code Issues Packages Projects Releases Wiki Activity

(svn r11454) -Fix: the CHANCE16 functions were biased; a 32768 in 65536 chance was really a 32769 in 65536 chance.

Browse Source
This commit is contained in:
rubidium 2007-11-17 23:16:41 +00:00
parent 76d9c20f01
commit ccf610e13c
2 changed files with 15 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/macros.h
View File

@ -476,7 +476,7 @@ template<typename T> static inline bool IS_INSIDE_1D(const T x, const int base,
* @param b The denominator of the fraction, must of course not be null * @param b The denominator of the fraction, must of course not be null
* @return True in (a/b) percent * @return True in (a/b) percent
*/ */
#define CHANCE16(a, b) ((uint16)Random() <= (uint16)((65536 * (a)) / (b))) #define CHANCE16(a, b) CHANCE16I(a, b, Random())
/** /**
* Flips a coin with a given probability and saves the randomize-number in a variable. * Flips a coin with a given probability and saves the randomize-number in a variable.
@ -484,18 +484,25 @@ template<typename T> static inline bool IS_INSIDE_1D(const T x, const int base,
* This macro uses the same parameters as the CHANCE16 marco. The third parameter * This macro uses the same parameters as the CHANCE16 marco. The third parameter
* must be a variable the randomize-number from Random() is saved in. * must be a variable the randomize-number from Random() is saved in.
* *
* The low 16 bits of r will already be used and can therefor not be passed to
* CHANCE16I. One can only send the high 16 bits to CHANCE16I.
*
* @param a The numerator of the fraction, see CHANCE16 * @param a The numerator of the fraction, see CHANCE16
* @param b The denominator of the fraction, see CHANCE16 * @param b The denominator of the fraction, see CHANCE16
* @param r The variable to save the randomize-number from Random() * @param r The variable to save the randomize-number from Random()
* @return True in (a/b) percent * @return True in (a/b) percent
*/ */
#define CHANCE16R(a, b, r) ((uint16)(r = Random()) <= (uint16)((65536 * (a)) / (b))) #define CHANCE16R(a, b, r) CHANCE16I(a, b, r = Random())
/** /**
* Checks if a given randomize-number is below a given probability. * Checks if a given randomize-number is below a given probability.
* *
* This macro is used to check if the given probability by the fraction of (a/b) * This macro is used to check if the given probability by the fraction of (a/b)
* is greater than the given randomize-number v. * is greater than low 16 bits of the given randomize-number v.
*
* Do not use this function twice on the same random 16 bits as it will yield
* the same result. One can use a random number for two calls to CHANCE16I,
* where one call sends the low 16 bits and the other the high 16 bits.
* *
* @param a The numerator of the fraction, see CHANCE16 * @param a The numerator of the fraction, see CHANCE16
* @param b The denominator of the fraction, see CHANCE16 * @param b The denominator of the fraction, see CHANCE16
@ -504,7 +511,7 @@ template<typename T> static inline bool IS_INSIDE_1D(const T x, const int base,
*/ */
static inline bool CHANCE16I(const uint a, const uint b, const uint32 r) static inline bool CHANCE16I(const uint a, const uint b, const uint32 r)
{ {
return (uint16)r <= (uint16)((65536 * a) / b); return (uint16)r < (uint16)((65536 * a) / b);
} }

10
src/town_cmd.cpp
View File

@ -731,16 +731,14 @@ no_slope:
* maybe terraform some. */ * maybe terraform some. */
desired_slope = (dir == DIAGDIR_NW || dir == DIAGDIR_SE) ? SLOPE_NW : SLOPE_NE; desired_slope = (dir == DIAGDIR_NW || dir == DIAGDIR_SE) ? SLOPE_NW : SLOPE_NE;
if (desired_slope != cur_slope && ComplementSlope(desired_slope) != cur_slope) { if (desired_slope != cur_slope && ComplementSlope(desired_slope) != cur_slope) {
uint32 r = Random(); if (CHANCE16(1, 8)) {
if (CHANCE16I(1, 8, r)) {
CommandCost res = CMD_ERROR; CommandCost res = CMD_ERROR;
if (!_generating_world && CHANCE16I(1, 10, r >> 4)) { if (!_generating_world && CHANCE16(1, 10)) {
/* Note: Do not replace " ^ 0xF" with ComplementSlope(). The slope might be steep. */ /* Note: Do not replace " ^ 0xF" with ComplementSlope(). The slope might be steep. */
res = DoCommand(tile, CHANCE16I(1, 16, r >> 8) ? cur_slope : cur_slope ^ 0xF, 0, res = DoCommand(tile, CHANCE16(1, 16) ? cur_slope : cur_slope ^ 0xF, 0,
DC_EXEC | DC_AUTO | DC_NO_WATER, CMD_TERRAFORM_LAND); DC_EXEC | DC_AUTO | DC_NO_WATER, CMD_TERRAFORM_LAND);
} }
if (CmdFailed(res) && CHANCE16I(1, 3, r >> 16)) { if (CmdFailed(res) && CHANCE16(1, 3)) {
/* We can consider building on the slope, though. */ /* We can consider building on the slope, though. */
goto no_slope; goto no_slope;
} }