empire/empserver
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

build: Fix inexact calculation of required materials

Browse source 
sector_can_build() computes mat[i] * (effic / 100.0).  The division is
inexact.  The result gets randomly rounded, so errors are vanishingly
unlikely to screw up material consumption.

However, we require the amount rounded up to be present since commit
1227d2c.  Errors *can* screw that up.  Fix by avoiding inexact
computation for that part.

We should probably review rounding of inexact values in general.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
This commit is contained in:
Markus Armbruster 2015-03-08 14:06:02 +01:00
parent c869c868e2
commit bfea5a2cf4
1 changed files with 9 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

17
src/lib/commands/buil.c
View file

@ -28,7 +28,7 @@
* *
* Known contributors to this file: * Known contributors to this file:
* Steve McClure, 1998-2000 * Steve McClure, 1998-2000
* Markus Armbruster, 2004-2014 * Markus Armbruster, 2004-2015
*/ */
#include <config.h> #include <config.h>
@ -652,8 +652,8 @@ static int
sector_can_build(struct sctstr *sp, short mat[], int work, sector_can_build(struct sctstr *sp, short mat[], int work,
int effic, char *what) int effic, char *what)
{ {
int i, avail, ret; int i, avail, ret, req;
double needed; double used;
if (player->god) if (player->god)
return 1; /* Deity builds ex nihilo */ return 1; /* Deity builds ex nihilo */
@ -674,14 +674,15 @@ sector_can_build(struct sctstr *sp, short mat[], int work,
ret = 1; ret = 1;
for (i = I_NONE + 1; i <= I_MAX; i++) { for (i = I_NONE + 1; i <= I_MAX; i++) {
needed = mat[i] * (effic / 100.0); used = mat[i] * effic;
if (sp->sct_item[i] < needed) { req = (used + 99) / 100;
pr("Not enough %s in %s (need %g more)\n", if (sp->sct_item[i] < req) {
pr("Not enough %s in %s (need %d more)\n",
ichr[i].i_name, xyas(sp->sct_x, sp->sct_y, player->cnum), ichr[i].i_name, xyas(sp->sct_x, sp->sct_y, player->cnum),
ceil(needed - sp->sct_item[i])); req - sp->sct_item[i]);
ret = 0; ret = 0;
} }
mat[i] = roundavg(needed); mat[i] = roundavg(used / 100.0);
} }
return ret; return ret;