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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 781, Thu Apr 7 23:07:09 2011 UTC revision 1350, Wed Jun 15 16:54:21 2011 UTC
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1    NOTE: GLK's approximate ranking of 8 most important tagged with
2    [GLK:1], [GLK:2], ...
3    
4  ========================  ========================
5  SHORT TERM =============  (for curvature-based VR)  SHORT TERM ============= (*needed* for streamlines & tractography)
6  ========================  ========================
7    
8  Outer products  Remove CL from compiler
     syntax [DONE]  
     typechecking  
     IL and codegen  
9    
10  Add M dot v, v dot M, and M dot N  [GLK:2] Add sequence types (needed for evals & evecs)
11        syntax
12            types: ty '{' INT '}'
13            value construction: '{' e1 ',' … ',' en '}'
14            indexing: e '{' e '}'
15    
16    [GLK:3] evals & evecs for symmetric tensor[2,2] and
17    tensor[3,3] (requires sequences)
18    
19    ability to emit/track/record variables into dynamically re-sized
20    runtime buffer
21    
22  Identity matrix [DONE up to code generation]  tensor fields: convolution on general tensor images
23    
24  trace [DONE]  ========================
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  extend norm (|exp|) to all tensor types  Allow ".ddro" file extensions in addition to ".diderot"
31    
32  extend normalize to all tensor types  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] Proper handling of stabilize method
37    
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    implicit type promotion of integers to reals where reals are
44    required (e.g. not exponentiation "^")
45    
46    [GLK:4] Save Diderot output to nrrd, instead of "mip.txt"
47      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
49      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
51        to index into complete list
52    
53    [GLK:5] Use of Teem's "hest" command-line parser for getting
54    any "input" variables that are not defined in the source file.
55    
56    [GLK:6] ability to declare a field so that probe positions are
57    *always* "inside"; with various ways of mapping the known image values
58    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  Use ∇⊗ etc syntax  Use ∇⊗ etc. syntax
71      syntax [DONE]      syntax [DONE]
72      typechecking      typechecking
73      IL and codegen      IL and codegen
74    
 Add sequence types  
     syntax  
         types: ty '{' INT '}'  
         value construction: '{' e1 ',' … ',' en '}'  
         indexing: e '{' e '}'  
   
 IL support for higher-order tensor values (matrices, etc).  
     tensor construction  
     tensor indexing and slicing  
     verify that hessians work correctly  
   
75  Add type aliases for color types  Add type aliases for color types
76      rgb = real{3}      rgb = real{3}
77      rgba = real{4}      rgba = real{4}
78    
 stabilize {} code block  
   
 DONE:  
   Infix dot product and cross product  
   lerp on scalars and vectors  
   
79  ==============================  ==============================
80  other SHORT TERM =============  (needed for LIC)  MEDIUM TERM ================== (*needed* for particles)
81  ==============================  ==============================
82    
83  vector fields: convolution on vector images  run-time birth of strands
84    
85  ==============================  "initially" supports lists
 MEDIUM TERM ================== (needed for streamlines & tractography)  
 ==============================  
86    
87  ability to emit/track/record variables into dynamically re-sized  "initially" supports lists of positions output from different
88  runtime buffer  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  evals & evecs for symmetric tensor[3,3]  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  tensor fields: convolution on general tensor images  ============================
100    MEDIUM-ISH TERM ============ (to make Diderot more useful/effective)
101    ============================
102    
103  ==============================  Python/ctypes interface to run-time
 other MEDIUM TERM ============ (needed for particles)  
 ==============================  
104    
105  run-time birth and death of strands  support for Python interop and GUI
106    
107  "initially" supports lists  Allow integer exponentiation ("^2") to apply to square matrices,
108    to represent repeated matrix multiplication
109    
110  "initially" supports lists of positions output from  Put small 1-D and 2-D fields, when reconstructed specifically by tent
111  different initalization Diderot program  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  spatial data structure that permits strands' queries of neighbors  expand trace in mid to low translation [DONE]
116    
117    extend norm (|exp|) to all tensor types [DONE for vectors and matrices]
118    
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
130    a variable name (get confusing error messages now)
131    
132  ==============================  ==============================
133  LONG TERM ====================  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
143    based on its actual use, instead of where the user defined it.  So,
144    for example, we should lift strand-invariant variables to global
145    scope.  Also prune out useless variables, which should include field
146    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  some indication of tensor symmetry  Permit field composition:
185      field#2(3)[3] warp = bspln3 ⊛ warpData;
186      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    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    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 =================
249    ======================
250    
251    test/zslice2.diderot:
252    // HEY (bug) bspln5 leads to problems ...
253    //  uncaught exception Size [size]
254    //    raised at c-target/c-target.sml:47.15-47.19
255    //field#4(3)[] F = img ⊛ bspln5;
256    

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