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adopt github pull request #286 - rndmonst()

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Eliminate the cache that was supporting rndmonst() and pick a random
monster in a single pass through mons[] via "weighted reservoir
sampling", a term I'm not familiar with.

It had a couple of bugs:  if the first monster examined happened to
be given a weighting of 0, rn2() would divide by 0.  I didn't try
to figure out how to trigger that.  But the second one was easy to
trigger:  if all eligible monsters were extinct or genocided, it
would issue a warning even though the situation isn't impossible.

Aside from fixing those, the rest is mostly as-is.  I included a bit
of formatting in decl.c, moved some declarations to not require C99,
and changed a couple of macros to not hide and duplicate a call to
level_difficulty().

Fixes #286
This commit is contained in:
PatR
2020-02-22 17:40:55 -08:00
parent 5d4b9784ac
commit cbdda9dc9d
10 changed files with 70 additions and 99 deletions
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1
doc/fixes37.0
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@@ -199,6 +199,7 @@ correct the Guidebook descriptions for msdos video_width and video_height to
state that they work with video:vesa; the video:vga setting that was
described there forces the 640x480x16 mode where video_width and
video_height don't operate (github #294)
redo rndmonst() to operate in a single pass (github pull request #286)
Code Cleanup and Reorganization

12
include/decl.h
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@@ -886,18 +886,19 @@ struct instance_globals {
boolean chosen_symset_end;
int symset_which_set;
/* SAVESIZE, BONESSIZE, LOCKNAMESIZE are defined in "fnamesiz.h" */
char SAVEF[SAVESIZE]; /* holds relative path of save file from playground */
char SAVEF[SAVESIZE]; /* relative path of save file from playground */
#ifdef MICRO
char SAVEP[SAVESIZE]; /* holds path of directory for save file */
#endif
char bones[BONESSIZE];
char lock[LOCKNAMESIZE];
/* hack.c */
anything tmp_anything;
int wc; /* current weight_cap(); valid after call to inv_weight() */
/* insight.c */
/* invent.c */
int lastinvnr; /* 0 ... 51 (never saved&restored) */
unsigned sortlootmode; /* set by sortloot() for use by sortloot_cmp();
@@ -905,7 +906,7 @@ struct instance_globals {
char *invbuf;
unsigned invbufsiz;
/* for perm_invent when operating on a partial inventory display, so that
the persistent one doesn't get shrunk during filtering for item selection
persistent one doesn't get shrunk during filtering for item selection
then regrown to full inventory, possibly being resized in the process */
winid cached_pickinv_win;
/* query objlist callback: return TRUE if obj type matches "this_type" */
@@ -916,15 +917,10 @@ struct instance_globals {
/* light.c */
light_source *light_base;
/* lock.c */
struct xlock_s xlock;
/* makemon.c */
struct {
int choice_count;
char mchoices[SPECIAL_PM]; /* value range is 0..127 */
} rndmonst_state;
/* mhitm.c */
boolean vis;

1
include/extern.h
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@@ -1216,7 +1216,6 @@ E void FDECL(dealloc_mextra, (struct monst *));
E struct monst *FDECL(makemon, (struct permonst *, int, int, int));
E boolean FDECL(create_critters, (int, struct permonst *, BOOLEAN_P));
E struct permonst *NDECL(rndmonst);
E void FDECL(reset_rndmonst, (int));
E struct permonst *FDECL(mkclass, (CHAR_P, int));
E struct permonst *FDECL(mkclass_aligned, (CHAR_P, int, ALIGNTYP_P));
E int FDECL(mkclass_poly, (int));

9
include/monst.h
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@@ -201,4 +201,13 @@ struct monst {
#define is_obj_mappear(mon,otyp) (M_AP_TYPE(mon) == M_AP_OBJECT \
&& (mon)->mappearance == (otyp))
/* Get the maximum difficulty monsters that can currently be generated,
given the current level difficulty and the hero's level. */
#define monmax_difficulty(levdif) (((levdif) + u.ulevel) / 2)
#define monmin_difficulty(levdif) ((levdif) / 6)
/* Macros for whether a type of monster is too strong for a specific level. */
#define montoostrong(monindx, lev) (mons[monindx].difficulty > lev)
#define montooweak(monindx, lev) (mons[monindx].difficulty < lev)
#endif /* MONST_H */

2
src/decl.c
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@@ -464,8 +464,6 @@ const struct instance_globals g_init = {
UNDEFINED_VALUES,
/* makemon.c */
{ -1, /* choice_count */
{ 0 } }, /* mchoices */
/* mhitm.c */
UNDEFINED_VALUE, /* vis */

1
src/do.c
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@@ -1453,7 +1453,6 @@ boolean at_stairs, falling, portal;
|| dunlev(&u.uz) < dunlev_reached(&u.uz))
dunlev_reached(&u.uz) = dunlev(&u.uz);
}
reset_rndmonst(NON_PM); /* u.uz change affects monster generation */
/* set default level change destination areas */
/* the special level code may override these */

2
src/exper.c
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@@ -215,7 +215,6 @@ const char *drainer; /* cause of death, if drain should be fatal */
pline("%s level %d.", Goodbye(), u.ulevel--);
/* remove intrinsic abilities */
adjabil(u.ulevel + 1, u.ulevel);
reset_rndmonst(NON_PM); /* new monster selection */
} else {
if (drainer) {
g.killer.format = KILLED_BY;
@@ -315,7 +314,6 @@ boolean incr; /* true iff via incremental experience growth */
if (u.ulevelmax < u.ulevel)
u.ulevelmax = u.ulevel;
adjabil(u.ulevel - 1, u.ulevel); /* give new intrinsics */
reset_rndmonst(NON_PM); /* new monster selection */
}
g.context.botl = TRUE;
}

138
src/makemon.c
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@@ -27,8 +27,6 @@ static boolean FDECL(makemon_rnd_goodpos, (struct monst *,
#define m_initsgrp(mtmp, x, y, mmf) m_initgrp(mtmp, x, y, 3, mmf)
#define m_initlgrp(mtmp, x, y, mmf) m_initgrp(mtmp, x, y, 10, mmf)
#define toostrong(monindx, lev) (mons[monindx].difficulty > lev)
#define tooweak(monindx, lev) (mons[monindx].difficulty < lev)
boolean
is_home_elemental(ptr)
@@ -945,7 +943,6 @@ boolean ghostly;
makeplural(mons[mndx].mname));
}
g.mvitals[mndx].mvflags |= G_EXTINCT;
reset_rndmonst(mndx);
}
return result;
}
@@ -1517,98 +1514,75 @@ struct permonst *
rndmonst()
{
register struct permonst *ptr;
register int mndx, ct;
register int mndx;
int weight, totalweight, selected_mndx, zlevel, minmlev, maxmlev;
boolean elemlevel, upper;
if (u.uz.dnum == quest_dnum && rn2(7) && (ptr = qt_montype()) != 0)
return ptr;
if (g.rndmonst_state.choice_count < 0) { /* need to recalculate */
int zlevel, minmlev, maxmlev;
boolean elemlevel;
boolean upper;
zlevel = level_difficulty();
minmlev = monmin_difficulty(zlevel);
maxmlev = monmax_difficulty(zlevel);
upper = Is_rogue_level(&u.uz); /* prefer uppercase only on rogue level */
elemlevel = In_endgame(&u.uz) && !Is_astralevel(&u.uz); /* elmntl plane */
g.rndmonst_state.choice_count = 0;
/* look for first common monster */
for (mndx = LOW_PM; mndx < SPECIAL_PM; mndx++) {
if (!uncommon(mndx))
break;
g.rndmonst_state.mchoices[mndx] = 0;
}
if (mndx == SPECIAL_PM) {
/* evidently they've all been exterminated */
debugpline0("rndmonst: no common mons!");
return (struct permonst *) 0;
} /* else `mndx' now ready for use below */
zlevel = level_difficulty();
/* determine the level of the weakest monster to make. */
minmlev = zlevel / 6;
/* determine the level of the strongest monster to make. */
maxmlev = (zlevel + u.ulevel) / 2;
upper = Is_rogue_level(&u.uz);
elemlevel = In_endgame(&u.uz) && !Is_astralevel(&u.uz);
/* amount processed so far */
totalweight = 0;
selected_mndx = NON_PM;
for (mndx = LOW_PM; mndx < SPECIAL_PM; ++mndx) {
ptr = &mons[mndx];
if (montooweak(mndx, minmlev) || montoostrong(mndx, maxmlev))
continue;
if (upper && !isupper((uchar) def_monsyms[(int) ptr->mlet].sym))
continue;
if (elemlevel && wrong_elem_type(ptr))
continue;
if (uncommon(mndx))
continue;
if (Inhell && (ptr->geno & G_NOHELL))
continue;
/*
* Find out how many monsters exist in the range we have selected.
* Weighted reservoir sampling: select ptr with a
* (ptr weight)/(total of all weights so far including ptr's)
* probability. For example, if the previous total is 10, and
* this is now looking at acid blobs with a frequency of 2, it
* has a 2/12 chance of abandoning ptr's previous value in favor
* of acid blobs, and 10/12 chance of keeping whatever it was.
*
* This does not bias results towards either the earlier or the
* later monsters: the smaller pool and better odds from being
* earlier are exactly canceled out by having more monsters to
* potentially steal its spot.
*/
for ( ; mndx < SPECIAL_PM; mndx++) { /* (`mndx' initialized above) */
ptr = &mons[mndx];
g.rndmonst_state.mchoices[mndx] = 0;
if (tooweak(mndx, minmlev) || toostrong(mndx, maxmlev))
continue;
if (upper && !isupper((uchar) def_monsyms[(int) ptr->mlet].sym))
continue;
if (elemlevel && wrong_elem_type(ptr))
continue;
if (uncommon(mndx))
continue;
if (Inhell && (ptr->geno & G_NOHELL))
continue;
ct = (int) (ptr->geno & G_FREQ) + align_shift(ptr);
if (ct < 0 || ct > 127)
panic("rndmonst: bad count [#%d: %d]", mndx, ct);
g.rndmonst_state.choice_count += ct;
g.rndmonst_state.mchoices[mndx] = (char) ct;
weight = (int) (ptr->geno & G_FREQ) + align_shift(ptr);
if (weight < 0 || weight > 127) {
impossible("bad weight in rndmonst for mndx %d", mndx);
weight = 0;
}
/* was unconditional, but if weight==0, rn2() < 0 will always fail;
also need to avoid rn2(0) if totalweight is still 0 so far */
if (weight > 0) {
totalweight += weight; /* totalweight now guaranteed to be > 0 */
if (rn2(totalweight) < weight)
selected_mndx = mndx;
}
/*
* Possible modification: if choice_count is "too low",
* expand minmlev..maxmlev range and try again.
*/
} /* choice_count+mchoices[] recalc */
if (g.rndmonst_state.choice_count <= 0) {
/* maybe no common mons left, or all are too weak or too strong */
debugpline1("rndmonst: choice_count=%d", g.rndmonst_state.choice_count);
return (struct permonst *) 0;
}
/*
* Now, select a monster at random.
* Possible modification: if totalweight is "too low" or nothing
* viable was picked, expand minmlev..maxmlev range and try again.
*/
ct = rnd(g.rndmonst_state.choice_count);
for (mndx = LOW_PM; mndx < SPECIAL_PM; mndx++)
if ((ct -= (int) g.rndmonst_state.mchoices[mndx]) <= 0)
break;
if (mndx == SPECIAL_PM || uncommon(mndx)) { /* shouldn't happen */
impossible("rndmonst: bad `mndx' [#%d]", mndx);
if (selected_mndx == NON_PM || uncommon(selected_mndx)) {
/* maybe no common monsters left, or all are too weak or too strong */
if (selected_mndx != NON_PM)
debugpline1("rndmonst returning Null [uncommon 'mndx'=#%d]",
selected_mndx);
return (struct permonst *) 0;
}
return &mons[mndx];
}
/* called when you change level (experience or dungeon depth) or when
monster species can no longer be created (genocide or extinction) */
void
reset_rndmonst(mndx)
int mndx; /* particular species that can no longer be created */
{
/* cached selection info is out of date */
if (mndx == NON_PM) {
g.rndmonst_state.choice_count = -1; /* full recalc needed */
} else if (mndx < SPECIAL_PM) {
g.rndmonst_state.choice_count -= g.rndmonst_state.mchoices[mndx];
g.rndmonst_state.mchoices[mndx] = 0;
} /* note: safe to ignore extinction of unique monsters */
return &mons[selected_mndx];
}
/* decide whether it's ok to generate a candidate monster by mkclass() */
@@ -1687,7 +1661,7 @@ aligntyp atyp;
(or lower) difficulty as preceding candidate (non-zero
'num' implies last > first so mons[last-1] is safe);
sometimes accept it even if high difficulty */
if (num && toostrong(last, maxmlev)
if (num && montoostrong(last, maxmlev)
&& mons[last].difficulty > mons[last - 1].difficulty
&& rn2(2))
break;

1
src/polyself.c
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@@ -299,7 +299,6 @@ newman()
change_sex();
adjabil(oldlvl, (int) u.ulevel);
reset_rndmonst(NON_PM); /* new monster generation criteria */
/* random experience points for the new experience level */
u.uexp = rndexp(FALSE);

2
src/read.c
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@@ -2107,7 +2107,6 @@ do_class_genocide()
* have G_GENOD or !G_GENO.
*/
g.mvitals[i].mvflags |= (G_GENOD | G_NOCORPSE);
reset_rndmonst(i);
kill_genocided_monsters();
update_inventory(); /* eggs & tins */
pline("Wiped out all %s.", nam);
@@ -2324,7 +2323,6 @@ int how;
} else if (ptr == g.youmonst.data) {
rehumanize();
}
reset_rndmonst(mndx);
kill_genocided_monsters();
update_inventory(); /* in case identified eggs were affected */
} else {