Commit e6cdd70df867f06 made the grid_dot structures for a grid no
longer be elements of the same array. But I didn't notice that
grid_edge_bydots_cmpfn was doing pointer subtraction on them on the
assumption that they were.
Fixed by comparing the dots' new index fields, which should correspond
exactly to their previous positions in the single array, so the
behaviour should be just what it was before the change.
The new generator works on the same 'combinatorial coordinates' system
as the more recently written Hats and Spectre generators.
When I came up with that technique for the Hats tiling, I was already
tempted to rewrite the Penrose generator on the same principle,
because it has a lot of advantages over the previous technique of
picking a randomly selected patch out of the subdivision of a huge
starting tile. It generates the exact limiting distribution of
possible tiling patches rather than an approximation based on how big
a tile you subdivided; it doesn't use any overly large integers or
overly precise floating point to suffer overflow or significance loss,
because it never has to even _think_ about the coordinates of any
point not in the actual output area.
But I resisted the temptation to throw out our existing Penrose
generator and move to the shiny new algorithm, for just one reason:
backwards compatibility. There's no sensible way to translate existing
Loopy game IDs into the new notation, so they would stop working,
unless we kept the old generator around as well to interpret the
previous system. And although _random seeds_ aren't guaranteed to
generate the same result from one build of Puzzles to the next, I do
try to keep existing descriptive game IDs working.
So if we had to keep the old generator around anyway, it didn't seem
worth writing a new one...
... at least, until we discovered that the old generator has a latent
bug. The function that decides whether each tile is within the target
area, and hence whether to make it part of the output grid, is based
on floating-point calculation of the tile's vertices. So a change in
FP rounding behaviour between two platforms could cause them to
interpret the same grid description differently, invalidating a Loopy
game on that grid. This is _unlikely_, as long as everyone uses IEEE
754 double, but the C standard doesn't actually guarantee that.
We found this out when I started investigating a slight distortion in
large instances of Penrose Loopy. For example, the Loopy random seed
"40x40t11#12345", as of just before this commit, generates a game
description beginning with the Penrose grid string "G-4944,5110,108",
in which you can see a star shape of five darts a few tiles down the
left edge, where two of the radii of the star don't properly line up
with edges in the surrounding shell of kites that they should be
collinear with. This turns out to be due to FP error: not because
_double precision_ ran out, but because the definitions of COS54,
SIN54, COS18 and SIN18 in penrose.c were specified to only 7 digits of
precision. And when you expand a patch of tiling that large, you end
up with integer combinations of those numbers with coefficients about
7 digits long, mostly cancelling out to leave a much smaller output
value, and the inaccuracies in those constants start to be noticeable.
But having noticed that, it then became clear that these badly
computed values were also critical to _correctness_ of the grid. So
they can't be fixed without invalidating old game IDs. _And_ then we
realised that this also means existing platforms might disagree on a
game ID's validity.
So if we have to break compatibility anyway, we should go all the way,
and instead of fixing the old system, introduce the shiny new system
that gets all of this right. Therefore, the new penrose.c uses the
more reliable combinatorial-coordinates system which doesn't deal in
integers that large in the first place. Also, there's no longer any
floating point at all in the calculation of tile vertex coordinates:
the combinations of 1 and sqrt(5) are computed exactly by the
n_times_root_k function. So now a large Penrose grid should never have
obvious failures of alignment like that.
The old system is kept for backwards compatibility. It's not fully
reliable, because that bug hasn't been fixed - but any Penrose Loopy
game ID that was working before on _some_ platform should still work
on that one. However, new Penrose Loopy game IDs are based on
combinatorial coordinates, computed in exact arithmetic, and should be
properly stable.
The new code looks suspiciously like the Spectre code (though
considerably simpler - the Penrose coordinate maps are easy enough
that I just hand-typed them rather than having an elaborate auxiliary
data-generation tool). That's because they were similar enough in
concept to make it possible to clone and hack. But there are enough
divergences that it didn't seem like a good idea to try to merge them
again afterwards - in particular, the fact that output Penrose tiles
are generated by merging two triangular metatiles while Spectres are
subdivisions of their metatiles.
I wanted these in order to try to check whether all the faces of a
grid were being traversed in the right orientation. That turned out
not to be the cause of my problem, but it's still useful information
to put in diagnostics.
Previously, the 'faces', 'edges' and 'dots' arrays in a grid structure
were arrays of actual grid_face, grid_edge and grid_dot structures,
physically containing all the data about the grid. But they also
referred to each other by pointers, which meant that they were hard to
realloc larger (you'd have to go through and rewrite all the pointers
whenever the base of an array moved). And _that_ meant that every grid
type had to figure out a reasonably good upper bound on the number of
all those things it was going to need, so that it could allocate those
arrays the right size to begin with, and not have to grow them
painfully later.
For some grid types - particularly the new aperiodic ones - that was
actually a painful part of the job. So I think enough is enough:
counting up how much memory you're going to need before using it is a
mug's game, and we should instead realloc on the fly.
So now g->faces, g->edges and g->dots have an extra level of
indirection. Instead of being arrays of actual structs, they're arrays
of pointers, and each struct in them is individually allocated. Once a
grid_face has been allocated, it never moves again, even if the array
of pointers changes size.
The old code had a common idiom of recovering the array index of a
particular element by subtracting it from the array base, e.g. writing
'f - g->faces' or 'e - g->edges'. To make that lookup remain possible,
I've added an 'index' field to each sub-structure, which is
initialised at the point where we decide what array index it will live
at.
This should involve no functional change, but the code that previously
had to figure out max_faces and max_dots up front for each grid type
is now completely gone, and nobody has to solve those problems in
advance any more.
This uses a tile shape very similar to the hat, but the tiling
_structure_ is totally changed so that there aren't any reflected
copies of the tile.
I'm not sure how much difference this makes to gameplay: the two
tilings are very similar for Loopy purposes. But the code was fun to
write, and I think the Spectre shape is noticeably prettier, so I'm
adding this to the collection anyway.
The test programs also generate a pile of SVG images used in the
companion article on my website.
This is preparing to separate out the auxiliary functionality, and
perhaps leave space for making more of it in future.
The previous name 'edsf' was too vague: the 'e' stood for 'extended',
and didn't say anything about _how_ it was extended. It's now called a
'flip dsf', since it tracks whether elements in the same class are
flipped relative to each other. More importantly, clients that are
going to use the flip tracking must say so when they allocate the dsf.
And Keen's need to track the minimal element of an equivalence class
is going to become a non-default feature, so there needs to be a new
kind of dsf that specially tracks those, and Keen will have to call it.
While I'm here, I've renamed the three dsf creation functions so that
they start with 'dsf_' like all the rest of the dsf API.
In this commit, 'DSF' is simply a typedef for 'int', so that the new
declaration form 'DSF *' translates to the same type 'int *' that dsfs
have always had. So all we're doing here is mechanically changing type
declarations throughout the code.
This fixes a build failure introduced by commit 2e48ce132e011e8
yesterday.
When I saw that commit I expected the most likely problem would be in
the NestedVM build, which is currently the thing with the most most
out-of-date C implementation. And indeed the NestedVM toolchain
doesn't have <tgmath.h> - but much more surprisingly, our _Windows_
builds failed too, with a compile error inside <tgmath.h> itself!
I haven't looked closely into the problem yet. Our Windows builds are
done with clang, which comes with its own <tgmath.h> superseding the
standard Windows one. So you'd _hope_ that clang could make sense of
its own header! But perhaps the problem is that this is an unusual
compile mode and hasn't been tested.
My fix is to simply add a cmake check for <tgmath.h> - which doesn't
just check the file's existence, it actually tries compiling a file
that #includes it, so it will detect 'file exists but is mysteriously
broken' just as easily as 'not there at all'. So this makes the builds
start working again, precisely on Ben's theory of opportunistically
using <tgmath.h> where possible and falling back to <math.h>
otherwise.
It looks ugly, though! I'm half tempted to make a new header file
whose job is to include a standard set of system headers, just so that
that nasty #ifdef doesn't have to sit at the top of almost all the
source files. But for the moment this at least gets the build working
again.
C89 provided only double-precision mathematical functions (sin() etc),
and so despite using single-precision elsewhere, those are what Puzzles
has traditionally used. C99 introduced single-precision equivalents
(sinf() etc), and I hope it's been long enough that we can safely use
them. Maybe they'll even be faster.
Rather than directly use the single-precision functions, though, we use
the magic macros from <tgmath.h> that automatically choose the precision
of mathematical functions based on their arguments. This has the
advantage that we only need to change which header we include, and thus
that we can switch back again if some platform has trouble with the new
header.
The big mathematical news this month is that a polygon has been
discovered that will tile the plane but only aperiodically. Penrose
tiles achieve this with two tile types; it's been an open question for
decades whether you could do it with only one tile. Now someone has
announced the discovery of such a thing, so _obviously_ this
mathematically exciting tiling ought to be one of the Loopy grid
options!
The polygon, named a 'hat' by its discoverers, consists of the union
of eight cells of the 'Kites' periodic tiling that Loopy already
implements. So all the vertex coordinates of the whole tiling are
vertices of the Kites grid, which makes handling the coordinates in an
exact manner a lot easier than Penrose tilings.
What's _harder_ than Penrose tilings is that, although this tiling can
be generated by a vaguely similar system of recursive expansion, the
expansion is geometrically distorting, which means you can't easily
figure out which tiles can be discarded early to save CPU. Instead
I've come up with a completely different system for generating a patch
of tiling, by using a hierarchical coordinate system to track a
location within many levels of the expansion process without ever
simulating the process as a whole. I'm really quite pleased with that
technique, and am tempted to try switching the Penrose generator over
to it too - except that we'd have to keep the old generator around to
stop old game ids being invalidated, and also, I think it would be
slightly trickier without an underlying fixed grid and without
overlaps in the tile expansion system.
However, before coming up with that, I got most of the way through
implementing the more obvious system of actually doing the expansions.
The result worked, but was very slow (because I changed approach
rather than try to implement tree-pruning under distortion). But the
code was reusable for two other useful purposes: it generated the
lookup tables needed for the production code, and it also generated a
lot of useful diagrams. So I've committed it anyway as a supporting
program, in a new 'aux' source subdirectory, and in aux/doc is a
writeup of the coordinate system's concepts, with all those diagrams.
(That's the kind of thing I'd normally put in a huge comment at the
top of the file, but doing all those diagrams in ASCII art would be
beyond miserable.)
From a gameplay perspective: the hat polygon has 13 edges, but one of
them has a vertex of the Kites tiling in the middle, and sometimes two
other tile boundaries meet at that vertex. I've chosen to represent
every hat as having degree 14 for Loopy purposes, because if you only
included that extra vertex when it was needed, then people would be
forever having to check whether this was a 13-hat or a 14-hat and it
would be nightmarish to play.
Even so, there's a lot of clicking involved to turn all those fiddly
individual edges on or off. This grid is noticeably nicer to play in
'autofollow' mode, by setting LOOPY_AUTOFOLLOW in the environment to
either 'fixed' or 'adaptive'. I'm tempted to make 'fixed' the default,
except that I think it would confuse players of ordinary square Loopy!
Every grid shape has its own limit, so this involved adding a new
interface between loopy.c and grid.c. The limits are based on ensuring
that the co-ordinate system of the grid doesn't overflow INT_MAX and
neither do the lengths of the face and dot arrays.
Though now I come to look at it I think the actual limits of grid.c are
much lower. Hmm.
A grid based on dodecagons with square symmetry. In between dodecagons
there are 4 triangles around 1 square, which resembles a compass rose.
https://en.wikipedia.org/wiki/3-4-3-12_tiling
A Floret grid of height h usually alternates columns of h hexagonal
florets with columns of h-1. An exception is when h=1, in which case
alternating columns of 1 and 0 florets would leave the grid
disconnected. So in that situation all columns have 1 floret in them,
and the starting y-coordinate oscillates to make the grid tile
sensibly.
However, that special case wasn't taken account of when calculating
the grid height. As a result the anomalous extra florets in the
height-1 tiling fell off the bottom of the puzzle window.
This is the main bulk of this boolification work, but although it's
making the largest actual change, it should also be the least
disruptive to anyone interacting with this code base downstream of me,
because it doesn't modify any interface between modules: all the
inter-module APIs were updated one by one in the previous commits.
This just cleans up the code within each individual source file to use
bool in place of int where I think that makes things clearer.
This commit removes the old #defines of TRUE and FALSE from puzzles.h,
and does a mechanical search-and-replace throughout the code to
replace them with the C99 standard lowercase spellings.
Regular hexagons and equilateral triangles in strict alternation, with
two of each interleaved around each vertex.
https://en.wikipedia.org/wiki/Trihexagonal_tiling
Thanks to Michael Quevillon for the patch.
Officially known as the '3-4-6-12 tiling', according to, e.g.,
https://en.wikipedia.org/wiki/3-4-6-12_tiling .
Thanks to Michael Quevillon for contributing this patch (and for
choosing a less hard-to-remember name for the tiling :-).
My Mac has just upgraded itself to include a version of clang which
warns if you use abs() on a floating-point value, or fabs() on an
integer. Fixed the two occurrences that came up in this build (and
which were actual build failures, because of -Werror), one in each
direction.
I think both were benign. The potentially dangerous one was using abs
in place of fabs in grid_find_incentre(), because that could actually
lose precision, but I think that function had plenty of precision to
spare (grid point separation being of the order of tens of pixels) so
nothing should have gone seriously wrong with the old code.
happening was that at the point of calling grid_make_consistent, the
grid had no faces or vertices, probably because grid_trim_vigorously
had removed them all, causing grid_make_consistent to try to allocate
a negative amount of memory and die in snewn.
Fixed by detecting this case in new_desc_penrose and retrying until
generation is successful. (It wasn't happening 100% of the time, just
_most_ of the time.) The same verification step is also used in
validate_desc_penrose in case a user manages to manually construct a
set of parameters leading to this failure mode.
[originally from svn r9840]
puzzle backend function which ought to have it, and propagate those
consts through to per-puzzle subroutines as needed.
I've recently had to do that to a few specific parameters which were
being misused by particular puzzles (r9657, r9830), which suggests
that it's probably a good idea to do the whole lot pre-emptively
before the next such problem shows up.
[originally from svn r9832]
[r9657 == 3b250baa02a7332510685948bf17576c397b8ceb]
[r9830 == 0b93de904a98f119b1a95d3a53029f1ed4bfb9b3]
meaning to revisit for a while. The new version generates more nicely
symmetric grids (best at even heights, but still improved even at odd
heights), and avoids any 'ears' on the grid (triangles at the corners
connected to only one other triangle, which tend to be boringly easy
places to start solving).
I've reused the grid-description-string mechanism invented for the
Penrose tilings as a versioning mechanism for the triangular grids, so
that old game descriptions should still be valid, and new triangular-
grid game descriptions begin with an "0_" prefix to indicate that they
are based on the new-style construction.
[originally from svn r9824]
4-vector representation, rather than mucking about with sines and
cosines after grid generation. _Should_ make no difference in the
generated grids (there's a theoretical risk of an unlucky rounding
error just about managing to push some point in or out of bounds, but
I think it's vanishingly small), but simplifies the coordinate-
flattening procedure, and in particular increases its chance of
getting vertical lines actually vertical.
(Prior to this change, the game ID
10x10t12:G2554,-31,108_a3b12h0a212a3d102b2a23a2e3b01b0a2c2a0c0 was
generating a not-quite-vertical edge at top left, in the Java port but
not on Linux; I suspect differences in sin and cos as the cause of the
discrepancy. With the rotation done like this, the points'
x-coordinates are now computed without reference to their
y-coordinates.)
[originally from svn r9168]
additions of missing 'static' and explicit 'void' in parameter lists,
plus one or two other things like explicitly casting chars in variadic
argument lists to int and using DBL_MAX if HUGE_VAL isn't available.
[originally from svn r9166]
to add two kinds of Penrose tiling to the grid types supported by
Loopy.
This has involved a certain amount of infrastructure work, because of
course the whole point of Penrose tilings is that they don't have to
be the same every time: so now grid.c has grown the capacity to
describe its grids as strings, and reconstitute them from those string
descriptions. Hence a Penrose Loopy game description consists of a
string identifying a particular piece of Penrose tiling, followed by
the normal Loopy clue encoding.
All the existing grid types decline to provide a grid description
string, so their Loopy game descriptions have not changed encoding.
[originally from svn r9159]
part that converts from abstract grid coordinates into screen
coordinates. This should speed up window-resizing by eliminating
pointless reiteration of the complicated part of the algorithm: now
when a game_drawstate is renewed, only the conversion into screen
coordinates has to be redone.
[originally from svn r9157]
overly complicated algorithm that uses it to home in on the grid edge
closest to a mouse click. That algorithm is being stressed beyond its
limit by the new grid type, and it's unnecessary anyway given that no
sensibly sized puzzle grid is going to be big enough to make it
prohibitively expensive just to do the trivial approach of iterating
over all edges and finding the closest of the eligible ones.
[originally from svn r9108]
on Windows at all?! Fix some departures from the C standard, mostly
declaring variables after a statement has already been issued in the
same block. MSVC is picky about this where gcc is forgiving, and TBH
I'd change the latter given the choice.
[originally from svn r8166]
Lambrou. Now capable of handling triangular and hexagonal grids as
well as square ones, and then a number of semiregular plane tilings
and duals of semiregular ones. In fact, most of the solver code
supports an _arbitrary_ planar graph (well, provided both the graph
and its dual have no self-edges), so it could easily be extended
further with only a little more effort.
[originally from svn r8162]
