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[diderot] Diff of /branches/pure-cfg/TODO
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Diff of /branches/pure-cfg/TODO

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revision 1046, Mon May 2 11:54:09 2011 UTC revision 1350, Wed Jun 15 16:54:21 2011 UTC
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1  NOTE: GLK's approximate ranking of 5 most imporant 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  SHORT TERM =============  (for curvature-based VR)  SHORT TERM ============= (*needed* for streamlines & tractography)
6  ========================  ========================
7    
8  IL support for higher-order tensor values (matrices, etc).  Remove CL from compiler
     tensor construction [DONE]  
     tensor indexing [DONE]  
     tensor slicing  
     verify that hessians work correctly [DONE]  
   
 Use ∇⊗ etc. syntax  
     syntax [DONE]  
     typechecking  
     IL and codegen  
9    
10  Add sequence types  [GLK:2] 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  ==============================  [GLK:3] evals & evecs for symmetric tensor[2,2] and
17  other SHORT TERM =============  (including needed for LIC)  tensor[3,3] (requires sequences)
 ==============================  
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  
21    
22  determinant ("det") for tensor[3,3]  tensor fields: convolution on general tensor images
23    
24  extend norm (|exp|) to all tensor types [DONE for vectors and matrices]  ========================
25    SHORT-ISH TERM ========= (to make using Diderot less annoying to
26    ========================  program in, and slow to execute)
27    
28  expand trace in mid to low translation  value-numbering optimization [DONE]
29    
30  value-numbering optimization  Allow ".ddro" file extensions in addition to ".diderot"
31    
32  Add type aliases for color types  Be able to output values of type tensor[2,2] and tensor[3,3];
33      rgb = real{3}  (currently only scalars & vectors).  Want to add some regression tests
34      rgba = real{4}  based on this and currently can't
35    
36  ==============================  [GLK:1] Proper handling of stabilize method
37  MEDIUM TERM ================== (including needed for streamlines & tractography)  
38  ==============================  allow "*" to represent "modulate": per-component multiplication of
39    vectors, and vectors only (not tensors of order 2 or higher).  Once
40    sequences are implemented this should be removed: the operation is not
41    invariant WRT basis so it is not a legit vector computation.
42    
43  [GLK:2] evals & evecs for symmetric tensor[3,3] (requires sequences)  implicit type promotion of integers to reals where reals are
44    required (e.g. not exponentiation "^")
45    
46  [GLK:3] Save Diderot output to nrrd, instead of "mip.txt"  [GLK:4] Save Diderot output to nrrd, instead of "mip.txt"
47    For grid of strands, save to similarly-shaped array    For grid of strands, save to similarly-shaped array
48    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
49    For ragged things (like tractography output), will need to save both    For ragged things (like tractography output), will need to save both
50      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
51      to index into complete list      to index into complete list
52    
53  [GLK:4] Use of Teem's "hest" command-line parser for getting  [GLK:5] Use of Teem's "hest" command-line parser for getting
54  any input variables that are not defined in the source file  any "input" variables that are not defined in the source file.
   
 [GLK:5] ability to declare a field in such a way so that probe  
 positions are *always* clamped to the support of "inside";  
 there are many cases where this is the sensible behavior.  
 (More generally, we could also have "repeat" declaration,  
 copying action of GL_REPEAT in texturing)  
   
 ability to emit/track/record variables into dynamically re-sized  
 runtime buffer  
55    
56  Want: allow X *= Y, X /= Y, X += Y, X -= Y to mean what they do in C,  [GLK:6] ability to declare a field so that probe positions are
57  provided that X*Y, X/Y, X+Y, X-Y are already supported.  *always* "inside"; with various ways of mapping the known image values
58  Nearly every Diderot program would be simplified by this.  to non-existant index locations.  One possible syntax emphasizes that
59    there is a index mapping function that logically precedes convolution:
60      F = bspln3 ⊛ (img ◦ clamp)
61      F = bspln3 ⊛ (img ◦ repeat)
62      F = bspln3 ⊛ (img ◦ mirror)
63    where "◦" or "∘" is used to indicate function composition
64    
65    Level of differentiability in field type should be statement about how
66    much differentiation the program *needs*, rather than what the kernel
67    *provides*.  The needed differentiability can be less than or equal to
68    the provided differentiability.
69    
70  Want: non-trivial field expressions & functions:  Use ∇⊗ etc. syntax
71    image(2)[2] Vimg = load(...);      syntax [DONE]
72    field#0(2)[] Vlen = |Vimg ⊛ bspln3|;      typechecking
73  to get a scalar field of vector length, or      IL and codegen
   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.  
74    
75  tensor fields: convolution on general tensor images  Add type aliases for color types
76        rgb = real{3}
77        rgba = real{4}
78    
79  ==============================  ==============================
80  other MEDIUM TERM ============ (needed for particles)  MEDIUM TERM ================== (*needed* for particles)
81  ==============================  ==============================
82    
83  run-time birth and death of strands  run-time birth of strands
84    
85  "initially" supports lists  "initially" supports lists
86    
87  "initially" supports lists of positions output from  "initially" supports lists of positions output from different
88  different initalization Diderot program  initalization Diderot program (or output from the same program;
89    e.g. using output of iso2d.diderot for one isovalue to seed the input
90    to another invocation of the same program)
91    
92    Communication between strands: they have to be able to learn each
93    other's state (at the previous iteration).  Early version of this can
94    have the network of neighbors be completely static (for running one
95    strand/pixel image computations).  Later version with strands moving
96    through the domain will require some spatial data structure to
97    optimize discovery of neighbors.
98    
99    ============================
100    MEDIUM-ISH TERM ============ (to make Diderot more useful/effective)
101    ============================
102    
103  spatial data structure that permits strands' queries of neighbors  Python/ctypes interface to run-time
104    
105  proper handling of stabilize method  support for Python interop and GUI
106    
107  test/vr-kcomp2.diderot: Add support for code like  Allow integer exponentiation ("^2") to apply to square matrices,
108    to represent repeated matrix multiplication
109    
110          (F1 if x else F2)@pos  Put small 1-D and 2-D fields, when reconstructed specifically by tent
111    and when differentiation is not needed, into faster texture buffers.
112    test/illust-vr.diderot is good example of program that uses multiple
113    such 1-D fields basically as lookup-table-based function evaluation
114    
115  This will require duplication of the continuation of the conditional  expand trace in mid to low translation [DONE]
 (but we should only duplicate over the live-range of the result of the  
 conditional.  
116    
117  ==============================  extend norm (|exp|) to all tensor types [DONE for vectors and matrices]
118  other MEDIUM TERM ============  
119  ==============================  determinant ("det") for tensor[3,3]
120    
121    add ":" for tensor dot product (contracts out two indices
122    instead of one like •), valid for all pairs of tensors with
123    at least two indices
124    
125    test/uninit.diderot:
126    documents need for better compiler error messages when output variables
127    are not initialized; the current messages are very cryptic
128    
129  want: warnings when "D" (reserved for differentiation) is declared as  want: warnings when "D" (reserved for differentiation) is declared as
130  a variable name (get confusing error messages now)  a variable name (get confusing error messages now)
131    
 support for Python interop and GUI  
   
 ==============================  
 LONG TERM ====================  
132  ==============================  ==============================
133    LONG TERM ==================== (make Diderot more interesting/attractive from
134    ==============================  a research standpoint)
135    
136    IL support for higher-order tensor values (matrices, etc).
137        tensor construction [DONE]
138        tensor indexing [DONE]
139        tensor slicing
140        verify that hessians work correctly [DONE]
141    
142  Better handling of variables that determines the scope of a variable  Better handling of variables that determines the scope of a variable
143  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 136  Line 145 
145  scope.  Also prune out useless variables, which should include field  scope.  Also prune out useless variables, which should include field
146  variables after the translation to mid-il.  variables after the translation to mid-il.
147    
148    test/vr-kcomp2.diderot: Add support for code like
149            (F1 if x else F2)@pos
150    This will require duplication of the continuation of the conditional
151    (but we should only duplicate over the live-range of the result of the
152    conditional.
153    
154    [GLK:7] Want: non-trivial field expressions & functions.
155    scalar fields from scalar fields F and G:
156      field#0(2)[] X = (sin(F) + 1.0)/2;
157      field#0(2)[] X = F*G;
158    scalar field of vector field magnitude:
159      image(2)[2] Vimg = load(...);
160      field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
161    field of normalized vectors (for LIC and vector field feature extraction)
162      field#2(2)[2] F = ...
163      field#0(2)[2] V = normalize(F);
164    scalar field of gradient magnitude (for edge detection))
165      field#2(2)[] F = Fimg ⊛ bspln3;
166      field#0(2)[] Gmag = |∇F|;
167    scalar field of squared gradient magnitude (simpler to differentiate):
168      field#2(2)[] F = Fimg ⊛ bspln3;
169      field#0(2)[] Gmsq = ∇F•∇F;
170    There is value in having these, even if the differentiation of them is
171    not supported (hence the indication of "field#0" for these above)
172    
173    Introduce region types (syntax region(d), where d is the dimension of the
174    region.  One useful operator would be
175            dom : field#k(d)[s] -> region(d)
176    Then the inside test could be written as
177            pos ∈ dom(F)
178    We could further extend this approach to allow geometric definitions of
179    regions.  It might also be useful to do inside tests in world space,
180    instead of image space.
181    
182  co- vs contra- index distinction  co- vs contra- index distinction
183    
184  add ":" for tensor dot product (contracts out two indices  Permit field composition:
185  instead of one like •), valid for all pairs of tensors with    field#2(3)[3] warp = bspln3 ⊛ warpData;
186  at least two indices    field#2(3)[] F = bspln3 ⊛ img;
187      field#2(3)[] Fwarp = F ◦ warp;
188    So Fwarp(x) = F(warp(X)).  Chain rule can be used for differentation.
189    This will be instrumental for expressing non-rigid registration
190    methods (but those will require co-vs-contra index distinction)
191    
192    Allow the convolution to be specified either as a single 1D kernel
193    (as we have it now):
194      field#2(3)[] F = bspln3 ⊛ img;
195    or, as a tensor product of kernels, one for each axis, e.g.
196      field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
197    This is especially important for things like time-varying fields
198    and the use of scale-space in field visualization: one axis of the
199    must be convolved with a different kernel during probing.
200    What is very unclear is how, in such cases, we should notate the
201    gradient, when we only want to differentiate with respect to some
202    subset of the axes.  One ambitious idea would be:
203      field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D time-varying field
204      field#0(2)[] F = lambda([x,y], Ft([x,y,42.0]))     // restriction to time=42.0
205      vec2 grad = ∇F([x,y]);                             // 2D gradient
206    
207    Tensors of order 3 (e.g. gradients of diffusion tensor fields, or
208    hessians of vector fields) and order 4 (e.g. Hessians of diffusion
209    tensor fields).
210    
211  some indication of tensor symmetry  representation of tensor symmetry
212  (have to identify the group of index permutations that are symmetries)  (have to identify the group of index permutations that are symmetries)
213    
214  dot works on all tensors  dot works on all tensors
215    
216  outer works on all tensors  outer works on all tensors
217    
218    Help for debugging Diderot programs: need to be able to uniquely
219    identify strands, and for particular strands that are known to behave
220    badly, do something like printf or other logging of their computations
221    and updates.
222    
223    Permit writing dimensionally general code: Have some statement of the
224    dimension of the world "W" (or have it be learned from one particular
225    field of interest), and then able to write "vec" instead of
226    "vec2/vec3", and perhaps "tensor[W,W]" instead of
227    "tensor[2,2]/tensor[3,3]"
228    
229    Traits: all things things that have boilerplate code (especially
230    volume rendering) should be expressed in terms of the unique
231    computational core.  Different kinds of streamline/tractography
232    computation will be another example, as well as particle systems.
233    
234  Einstein summation notation  Einstein summation notation
235    
236  "tensor comprehension" (like list comprehension)  "tensor comprehension" (like list comprehension)
237    
238  Python/ctypes interface to run-time  Fields coming from different sources of data:
239    * triangular or tetrahedral meshes over 2D or 3D domains (of the
240      source produced by finite-element codes; these will come with their
241      own specialized kinds of reconstruction kernels, called "basis
242      functions" in this context)
243    * Large point clouds, with some radial basis function around each point,
244      which will be tuned by parameters of the point (at least one parameter
245      giving some notion of radius)
246    
247  ======================  ======================
248  BUGS =================  BUGS =================
249  ======================  ======================
250    
 [GLK:1] test/fields.diderot:  
 documents various bugs/questions associated with simple field expressions  
 (negation, addition, scalar multiplication)  
   
 test/read2vecs.diderot:  
 // 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  
 image(2)[] Vimg = load("../data/vorttest.nrrd");  
   
251  test/zslice2.diderot:  test/zslice2.diderot:
252  // HEY (bug) bspln5 leads to problems ...  // HEY (bug) bspln5 leads to problems ...
253  //  uncaught exception Size [size]  //  uncaught exception Size [size]
254  //    raised at c-target/c-target.sml:47.15-47.19  //    raised at c-target/c-target.sml:47.15-47.19
255  //field#4(3)[] F = img ⊛ bspln5;  //field#4(3)[] F = img ⊛ bspln5;
256    

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