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

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revision 1156, Sun May 8 21:20:52 2011 UTC revision 1295, Thu Jun 9 06:42:54 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  SHORT TERM ============= (*needed* for streamlines & tractography)  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  [GLK:1] evals & evecs for symmetric tensor[3,3] (requires sequences)  
16    [GLK:4] 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  ability to emit/track/record variables into dynamically re-sized
20  runtime buffer  runtime buffer
# Line 18  Line 22 
22  tensor fields: convolution on general tensor images  tensor fields: convolution on general tensor images
23    
24  ========================  ========================
25  SHORT-ISH TERM ========= (to make using Diderot less annoying/slow)  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  value-numbering optimization  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  proper handling of stabilize method  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 so that probe positions are  [GLK:7] ability to declare a field so that probe positions are
69  *always* "inside"; with various ways of mapping the known image values  *always* "inside"; with various ways of mapping the known image values
70  to non-existant index locations.  One possible syntax emphasizes that  to non-existant index locations.  One possible syntax emphasizes that
71  there is a index mapping function that logically precedes convolution:  there is a index mapping function that logically precedes convolution:
72    F = bspln3 ⊛ (img  clamp)    F = bspln3 ⊛ (img ◦ clamp)
73    F = bspln3 ⊛ (img ◦ repeat)    F = bspln3 ⊛ (img ◦ repeat)
74    F = bspln3 ⊛ (img ◦ mirror)    F = bspln3 ⊛ (img ◦ mirror)
75  where "◦" or "∘" is used to indicate function composition  where "◦" or "∘" is used to indicate function composition
76    
 Use ∇⊗ etc. syntax  
     syntax [DONE]  
     typechecking  
     IL and codegen  
   
 Add a clamp function, which takes three arguments; either three scalars:  
   clamp(x, minval, maxval)  = max(minval, min(maxval, x))  
 or three vectors of the same size:  
   clamp([x,y], minvec, maxvec)  = [max(minvec[0], min(maxvec[0], x)),  
                                    max(minvec[1], min(maxvec[1], y))]  
 This would be useful in many current Diderot programs.  
 One question: clamp(x, minval, maxval) is the argument order  
 used in OpenCL and other places, but clamp(minval, maxval, x)  
 would be more consistent with lerp(minout, maxout, x).  
   
77  Level of differentiability in field type should be statement about how  Level of differentiability in field type should be statement about how
78  much differentiation the program *needs*, rather than what the kernel  much differentiation the program *needs*, rather than what the kernel
79  *provides*.  The needed differentiability can be less than or equal to  *provides*.  The needed differentiability can be less than or equal to
80  the provided differentiability.  the provided differentiability.
81    
82    Use ∇⊗ etc. syntax
83        syntax [DONE]
84        typechecking
85        IL and codegen
86    
87  Add type aliases for color types  Add type aliases for color types
88      rgb = real{3}      rgb = real{3}
89      rgba = real{4}      rgba = real{4}
# Line 76  Line 96 
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  Communication between strands: they have to be able to learn each
105  other's state (at the previous iteration).  Early version of this can  other's state (at the previous iteration).  Early version of this can
# Line 94  Line 116 
116    
117  support for Python interop and GUI  support for Python interop and GUI
118    
119    Allow integer exponentiation ("^2") to apply to square matrices,
120    to represent repeated matrix multiplication
121    
122  Alow X *= Y, X /= Y, X += Y, X -= Y to mean what they do in C,  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.  provided that X*Y, X/Y, X+Y, X-Y are already supported.
124  Nearly every Diderot program would be simplified by this.  Nearly every Diderot program would be simplified by this.
# Line 142  Line 167 
167  (but we should only duplicate over the live-range of the result of the  (but we should only duplicate over the live-range of the result of the
168  conditional.  conditional.
169    
170  [GLK:5] Want: non-trivial field expressions & functions:  [GLK:8] Want: non-trivial field expressions & functions.
171    scalar fields from scalar fields F and G:
172      field#0(2)[] X = (sin(F) + 1.0)/2;
173      field#0(2)[] X = F*G;
174    scalar field of vector field magnitude:
175    image(2)[2] Vimg = load(...);    image(2)[2] Vimg = load(...);
176    field#0(2)[] Vlen = |Vimg ⊛ bspln3|;    field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
177  to get a scalar field of vector length, or  field of normalized vectors (for LIC and vector field feature extraction)
178      field#2(2)[2] F = ...
179      field#0(2)[2] V = normalize(F);
180    scalar field of gradient magnitude (for edge detection))
181    field#2(2)[] F = Fimg ⊛ bspln3;    field#2(2)[] F = Fimg ⊛ bspln3;
182    field#0(2)[] Gmag = |∇F|;    field#0(2)[] Gmag = |∇F|;
183  to get a scalar field of gradient magnitude, or  scalar field of squared gradient magnitude (simpler to differentiate):
184    field#2(2)[] F = Fimg ⊛ bspln3;    field#2(2)[] F = Fimg ⊛ bspln3;
185    field#0(2)[] Gmsq = ∇F•∇F;    field#0(2)[] Gmsq = ∇F•∇F;
186  to get a scalar field of squared gradient magnitude, which is simpler  There is value in having these, even if the differentiation of them is
187  to differentiate.  However, there is value in having these, even if  not supported (hence the indication of "field#0" for these above)
 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.  
188    
189  Permit fields composition, especially for warping images by a  Introduce region types (syntax region(d), where d is the dimension of the
190  smooth field of deformation vectors  region.  One useful operator would be
191            dom : field#k(d)[s] -> region(d)
192    Then the inside test could be written as
193            pos ∈ dom(F)
194    We could further extend this approach to allow geometric definitions of
195    regions.  It might also be useful to do inside tests in world space,
196    instead of image space.
197    
198    co- vs contra- index distinction
199    
200    Permit field composition:
201    field#2(3)[3] warp = bspln3 ⊛ warpData;    field#2(3)[3] warp = bspln3 ⊛ warpData;
202    field#2(3)[] F = bspln3 ⊛ img;    field#2(3)[] F = bspln3 ⊛ img;
203    field#2(3)[] Fwarp = F ◦ warp;    field#2(3)[] Fwarp = F ◦ warp;
204  So Fwarp(x) = F(warp(X)).  Chain rule can be used for differentation  So Fwarp(x) = F(warp(X)).  Chain rule can be used for differentation.
205    This will be instrumental for expressing non-rigid registration
206    methods (but those will require co-vs-contra index distinction)
207    
208  Allow the convolution to be specified either as a single 1D kernel  Allow the convolution to be specified either as a single 1D kernel
209  (as we have it now):  (as we have it now):
210    field#2(3)[] F = bspln3 ⊛ img;    field#2(3)[] F = bspln3 ⊛ img;
211  or, as a tensor product of kernels, one for each axis, e.g.  or, as a tensor product of kernels, one for each axis, e.g.
212    field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;    field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
213  This is especially important for things like time-varying data, or  This is especially important for things like time-varying fields
214  other multi-dimensional fields where one axis of the domain is very  and the use of scale-space in field visualization: one axis of the
215  different from the rest.  What is very unclear is how, in such cases,  must be convolved with a different kernel during probing.
216  we should notate the gradient, when we only want to differentiate with  What is very unclear is how, in such cases, we should notate the
217  respect to some of the axes.  gradient, when we only want to differentiate with respect to some
218    subset of the axes.  One ambitious idea would be:
219      field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D time-varying field
220      field#0(2)[] F = lambda([x,y], Ft([x,y,42.0]))     // restriction to time=42.0
221      vec2 grad = ∇F([x,y]);                             // 2D gradient
222    
223    Tensors of order 3 (e.g. gradients of diffusion tensor fields, or
224    hessians of vector fields) and order 4 (e.g. Hessians of diffusion
225    tensor fields).
226    
227  co- vs contra- index distinction  representation of tensor symmetry
   
 some indication of tensor symmetry  
228  (have to identify the group of index permutations that are symmetries)  (have to identify the group of index permutations that are symmetries)
229    
230  dot works on all tensors  dot works on all tensors
231    
232  outer works on all tensors  outer works on all tensors
233    
234    Help for debugging Diderot programs: need to be able to uniquely
235    identify strands, and for particular strands that are known to behave
236    badly, do something like printf or other logging of their computations
237    and updates.
238    
239    Permit writing dimensionally general code: Have some statement of the
240    dimension of the world "W" (or have it be learned from one particular
241    field of interest), and then able to write "vec" instead of
242    "vec2/vec3", and perhaps "tensor[W,W]" instead of
243    "tensor[2,2]/tensor[3,3]"
244    
245    Traits: all things things that have boilerplate code (especially
246    volume rendering) should be expressed in terms of the unique
247    computational core.  Different kinds of streamline/tractography
248    computation will be another example, as well as particle systems.
249    
250  Einstein summation notation  Einstein summation notation
251    
252  "tensor comprehension" (like list comprehension)  "tensor comprehension" (like list comprehension)
253    
254    Fields coming from different sources of data:
255    * triangular or tetrahedral meshes over 2D or 3D domains (of the
256      source produced by finite-element codes; these will come with their
257      own specialized kinds of reconstruction kernels, called "basis
258      functions" in this context)
259    * Large point clouds, with some radial basis function around each point,
260      which will be tuned by parameters of the point (at least one parameter
261      giving some notion of radius)
262    
263  ======================  ======================
264  BUGS =================  BUGS =================
265  ======================  ======================

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