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[diderot] Diff of /branches/vis12-cl/TODO
 [diderot] / branches / vis12-cl / TODO

# Diff of /branches/vis12-cl/TODO

revision 1115, Thu May 5 04:42:18 2011 UTC revision 1301, Thu Jun 9 23:58:40 2011 UTC
# Line 1  Line 1
1  NOTE: GLK's approximate ranking of 5 most important tagged with  NOTE: GLK's approximate ranking of 8 most important tagged with
2  [GLK:1], [GLK:2], ...  [GLK:1], [GLK:2], ...
3
4  ==============================  ========================
5  other SHORT TERM =============  (including needed for LIC)  SHORT TERM ============= (*needed* for streamlines & tractography)
6  ==============================  ========================
7
8  [GLK:1] Add sequence types (needed for evals & evecs)  Remove CL from compiler
9
10    [GLK:3] Add sequence types (needed for evals & evecs)
11      syntax      syntax
12          types: ty '{' INT '}'          types: ty '{' INT '}'
13          value construction: '{' e1 ',' … ',' en '}'          value construction: '{' e1 ',' … ',' en '}'
14          indexing: e '{' e '}'          indexing: e '{' e '}'
15
16  IL support for higher-order tensor values (matrices, etc).  [GLK:4] evals & evecs for symmetric tensor[2,2] and
17      tensor construction [DONE]  tensor[3,3] (requires sequences)
tensor indexing [DONE]
tensor slicing
verify that hessians work correctly [DONE]

Use ∇⊗ etc. syntax
syntax [DONE]
typechecking
IL and codegen
18
19  test/uninit.diderot:  ability to emit/track/record variables into dynamically re-sized
20  documents need for better compiler error messages when output variables  runtime buffer
are not initialized; the current messages are very cryptic

determinant ("det") for tensor[3,3]

expand trace in mid to low translation

value-numbering optimization
21
22  Add type aliases for color types  tensor fields: convolution on general tensor images
rgb = real{3}
rgba = real{4}
23
24  ==============================  ========================
25  MEDIUM TERM ================== (including needed for streamlines & tractography)  SHORT-ISH TERM ========= (to make using Diderot less annoying to
26  ==============================  ========================  program in, and slow to execute)
27
28    value-numbering optimization [DONE]
29
30    Allow ".ddro" file extensions in addition to ".diderot"
31
32    Be able to output values of type tensor[2,2] and tensor[3,3];
33    (currently only scalars & vectors).  Want to add some regression tests
34    based on this and currently can't
35
36    [GLK:1] Add a clamp function, which takes three arguments; either
37    three scalars:
38      clamp(lo, hi, x)  = max(lo, min(hi, x))
39    or three vectors of the same size:
40      clamp(lo, hi, [x,y])  = [max(lo[0], min(hi[0], x)),
41                               max(lo[1], min(hi[1], y))]
42    This would be useful in many current Diderot programs.
43    One question: clamp(x, lo, hi) is the argument order used in OpenCL
44    and other places, but clamp(lo, hi, x) is much more consistent with
45    lerp(lo, hi, x), hence GLK's preference
46    [DONE]
47
48    [GLK:2] Proper handling of stabilize method
49
50    allow "*" to represent "modulate": per-component multiplication of
51    vectors, and vectors only (not tensors of order 2 or higher).  Once
52    sequences are implemented this should be removed: the operation is not
53    invariant WRT basis so it is not a legit vector computation.
54
55  [GLK:1] evals & evecs for symmetric tensor[3,3] (requires sequences)  implicit type promotion of integers to reals where reals are
56    required (e.g. not exponentiation "^")
57
58  [GLK:2] Save Diderot output to nrrd, instead of "mip.txt"  [GLK:5] Save Diderot output to nrrd, instead of "mip.txt"
59    For grid of strands, save to similarly-shaped array    For grid of strands, save to similarly-shaped array
60    For list of strands, save to long 1-D (or 2-D for non-scalar output) list    For list of strands, save to long 1-D (or 2-D for non-scalar output) list
61    For ragged things (like tractography output), will need to save both    For ragged things (like tractography output), will need to save both
62      complete list of values, as well as list of start indices and lengths      complete list of values, as well as list of start indices and lengths
63      to index into complete list      to index into complete list
64
65  [GLK:3] Use of Teem's "hest" command-line parser for getting  [GLK:6] Use of Teem's "hest" command-line parser for getting
66  any input variables that are not defined in the source file  any "input" variables that are not defined in the source file.
67
68  [GLK:4] ability to declare a field in such a way so that probe  [GLK:7] ability to declare a field so that probe positions are
69  positions are *always* clamped to the support of "inside";  *always* "inside"; with various ways of mapping the known image values
70  there are many cases where this is the sensible behavior.  to non-existant index locations.  One possible syntax emphasizes that
71  (could also have "repeat" declaration, to mimic GL_REPEAT texturing)  there is a index mapping function that logically precedes convolution:
72      F = bspln3 ⊛ (img ◦ clamp)
73      F = bspln3 ⊛ (img ◦ repeat)
74      F = bspln3 ⊛ (img ◦ mirror)
75    where "◦" or "∘" is used to indicate function composition
76
77    Level of differentiability in field type should be statement about how
78    much differentiation the program *needs*, rather than what the kernel
79    *provides*.  The needed differentiability can be less than or equal to
80    the provided differentiability.
81
82  extend norm (|exp|) to all tensor types [DONE for vectors and matrices]  Use ∇⊗ etc. syntax
83        syntax [DONE]
84  ability to emit/track/record variables into dynamically re-sized      typechecking
85  runtime buffer      IL and codegen

Want: allow X *= Y, X /= Y, X += Y, X -= Y to mean what they do in C,
provided that X*Y, X/Y, X+Y, X-Y are already supported.
Nearly every Diderot program would be simplified by this.

Want: non-trivial field expressions & functions:
field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
to get a scalar field of vector length, or
field#2(2)[] F = Fimg ⊛ bspln3;
field#0(2)[] Gmag = |∇F|;
to get a scalar field of gradient magnitude, or
field#2(2)[] F = Fimg ⊛ bspln3;
field#0(2)[] Gmsq = ∇F•∇F;
to get a scalar field of squared gradient magnitude, which is simpler
to differentiate.  However, there is value in having these, even if
the differentiation of them is not supported (hence the indication
of "field#0" for these above)

Want: ability to apply "normalize" to a field itself, e.g.
field#0(2)[2] V = normalize(Vimg ⊛ ctmr);
so that V(x) = normalize((Vimg ⊛ ctmr)(x)).
Having this would simplify expression of standard LIC method, and
would also help express other vector field expressions that arise
in vector field feature exraction.
86
87  tensor fields: convolution on general tensor images  Add type aliases for color types
88        rgb = real{3}
89        rgba = real{4}
90
91  ==============================  ==============================
92  other MEDIUM TERM ============ (needed for particles)  MEDIUM TERM ================== (*needed* for particles)
93  ==============================  ==============================
94
[GLK:5] run-time death of strands; test/iso2d.diderot provides
great initial test for "die" command.

95  run-time birth of strands  run-time birth of strands
96
97  "initially" supports lists  "initially" supports lists
98
99  "initially" supports lists of positions output from  "initially" supports lists of positions output from different
100  different initalization Diderot program  initalization Diderot program (or output from the same program;
101    e.g. using output of iso2d.diderot for one isovalue to seed the input
102    to another invocation of the same program)
103
104    Communication between strands: they have to be able to learn each
105    other's state (at the previous iteration).  Early version of this can
106    have the network of neighbors be completely static (for running one
107    strand/pixel image computations).  Later version with strands moving
108    through the domain will require some spatial data structure to
109    optimize discovery of neighbors.
110
111    ============================
112    MEDIUM-ISH TERM ============ (to make Diderot more useful/effective)
113    ============================
114
115  spatial data structure that permits strands' queries of neighbors  Python/ctypes interface to run-time
116
117  proper handling of stabilize method  support for Python interop and GUI
118
119  test/vr-kcomp2.diderot: Add support for code like  Allow integer exponentiation ("^2") to apply to square matrices,
120    to represent repeated matrix multiplication
121
122          (F1 if x else F2)@pos  Alow X *= Y, X /= Y, X += Y, X -= Y to mean what they do in C,
123    provided that X*Y, X/Y, X+Y, X-Y are already supported.
124    Nearly every Diderot program would be simplified by this.
125    [DONE]
126
127  This will require duplication of the continuation of the conditional  Put small 1-D and 2-D fields, when reconstructed specifically by tent
128  (but we should only duplicate over the live-range of the result of the  and when differentiation is not needed, into faster texture buffers.
129  conditional.  test/illust-vr.diderot is good example of program that uses multiple
130    such 1-D fields basically as lookup-table-based function evaluation
131
132    expand trace in mid to low translation [DONE]
133
134    extend norm (|exp|) to all tensor types [DONE for vectors and matrices]
135
136    determinant ("det") for tensor[3,3]
137
138  add ":" for tensor dot product (contracts out two indices  add ":" for tensor dot product (contracts out two indices
139  instead of one like •), valid for all pairs of tensors with  instead of one like •), valid for all pairs of tensors with
140  at least two indices  at least two indices
141
142  ==============================  test/uninit.diderot:
143  other MEDIUM TERM ============  documents need for better compiler error messages when output variables
144  ==============================  are not initialized; the current messages are very cryptic
145
146  want: warnings when "D" (reserved for differentiation) is declared as  want: warnings when "D" (reserved for differentiation) is declared as
147  a variable name (get confusing error messages now)  a variable name (get confusing error messages now)
148
support for Python interop and GUI

Python/ctypes interface to run-time

==============================
LONG TERM ====================
149  ==============================  ==============================
150    LONG TERM ==================== (make Diderot more interesting/attractive from
151    ==============================  a research standpoint)
152
153    IL support for higher-order tensor values (matrices, etc).
154        tensor construction [DONE]
155        tensor indexing [DONE]
156        tensor slicing
157        verify that hessians work correctly [DONE]
158
159  Better handling of variables that determines the scope of a variable  Better handling of variables that determines the scope of a variable
160  based on its actual use, instead of where the user defined it.  So,  based on its actual use, instead of where the user defined it.  So,
# Line 140  Line 162
162  scope.  Also prune out useless variables, which should include field  scope.  Also prune out useless variables, which should include field
163  variables after the translation to mid-il.  variables after the translation to mid-il.
164
165    test/vr-kcomp2.diderot: Add support for code like
166            (F1 if x else F2)@pos
167    This will require duplication of the continuation of the conditional
168    (but we should only duplicate over the live-range of the result of the
169    conditional.
170
171    [GLK:8] Want: non-trivial field expressions & functions.
172    scalar fields from scalar fields F and G:
173      field#0(2)[] X = (sin(F) + 1.0)/2;
174      field#0(2)[] X = F*G;
175    scalar field of vector field magnitude:
177      field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
178    field of normalized vectors (for LIC and vector field feature extraction)
179      field#2(2)[2] F = ...
180      field#0(2)[2] V = normalize(F);
181    scalar field of gradient magnitude (for edge detection))
182      field#2(2)[] F = Fimg ⊛ bspln3;
183      field#0(2)[] Gmag = |∇F|;
184    scalar field of squared gradient magnitude (simpler to differentiate):
185      field#2(2)[] F = Fimg ⊛ bspln3;
186      field#0(2)[] Gmsq = ∇F•∇F;
187    There is value in having these, even if the differentiation of them is
188    not supported (hence the indication of "field#0" for these above)
189
190    Introduce region types (syntax region(d), where d is the dimension of the
191    region.  One useful operator would be
192            dom : field#k(d)[s] -> region(d)
193    Then the inside test could be written as
194            pos ∈ dom(F)
195    We could further extend this approach to allow geometric definitions of
196    regions.  It might also be useful to do inside tests in world space,
198
199  co- vs contra- index distinction  co- vs contra- index distinction
200
201  some indication of tensor symmetry  Permit field composition:
202      field#2(3)[3] warp = bspln3 ⊛ warpData;
203      field#2(3)[] F = bspln3 ⊛ img;
204      field#2(3)[] Fwarp = F ◦ warp;
205    So Fwarp(x) = F(warp(X)).  Chain rule can be used for differentation.
206    This will be instrumental for expressing non-rigid registration
207    methods (but those will require co-vs-contra index distinction)
208
209    Allow the convolution to be specified either as a single 1D kernel
210    (as we have it now):
211      field#2(3)[] F = bspln3 ⊛ img;
212    or, as a tensor product of kernels, one for each axis, e.g.
213      field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
214    This is especially important for things like time-varying fields
215    and the use of scale-space in field visualization: one axis of the
216    must be convolved with a different kernel during probing.
217    What is very unclear is how, in such cases, we should notate the
218    gradient, when we only want to differentiate with respect to some
219    subset of the axes.  One ambitious idea would be:
220      field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D time-varying field
221      field#0(2)[] F = lambda([x,y], Ft([x,y,42.0]))     // restriction to time=42.0
223
224    Tensors of order 3 (e.g. gradients of diffusion tensor fields, or
225    hessians of vector fields) and order 4 (e.g. Hessians of diffusion
226    tensor fields).
227
228    representation of tensor symmetry
229  (have to identify the group of index permutations that are symmetries)  (have to identify the group of index permutations that are symmetries)
230
231  dot works on all tensors  dot works on all tensors
232
233  outer works on all tensors  outer works on all tensors
234
235    Help for debugging Diderot programs: need to be able to uniquely
236    identify strands, and for particular strands that are known to behave
237    badly, do something like printf or other logging of their computations
239
240    Permit writing dimensionally general code: Have some statement of the
241    dimension of the world "W" (or have it be learned from one particular
242    field of interest), and then able to write "vec" instead of
243    "vec2/vec3", and perhaps "tensor[W,W]" instead of
244    "tensor[2,2]/tensor[3,3]"
245
246    Traits: all things things that have boilerplate code (especially
247    volume rendering) should be expressed in terms of the unique
248    computational core.  Different kinds of streamline/tractography
249    computation will be another example, as well as particle systems.
250
251  Einstein summation notation  Einstein summation notation
252
253  "tensor comprehension" (like list comprehension)  "tensor comprehension" (like list comprehension)
254
255    Fields coming from different sources of data:
256    * triangular or tetrahedral meshes over 2D or 3D domains (of the
257      source produced by finite-element codes; these will come with their
258      own specialized kinds of reconstruction kernels, called "basis
259      functions" in this context)
260    * Large point clouds, with some radial basis function around each point,
261      which will be tuned by parameters of the point (at least one parameter
262      giving some notion of radius)
263
264  ======================  ======================
265  BUGS =================  BUGS =================
266  ======================  ======================
267
test/bug-usevar.diderot:
looks like varialble scoping bug is still present in some cases?

test/bug-matrix.diderot:
3x3 matrix subtraction is broken

// HEY (BUG?) shouldn't it be a type error to load this 2-D array of
// 2-vectors into a 2-D *scalar* field?  Instead, get:
//   uncaught exception Fail [Fail: Error in compiling lic.diderot]
//     raised at driver/main.sml:31.39-31.76