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[diderot] Diff of /branches/charisee/TODO
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Diff of /branches/charisee/TODO

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revision 1156, Sun May 8 21:20:52 2011 UTC revision 1257, Tue May 24 18:47:46 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    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    
47    [GLK:2] Proper handling of stabilize method
48    
49  value-numbering optimization  allow "*" to represent "modulate": per-component multiplication of
50    vectors, and vectors only (not tensors of order 2 or higher).  Once
51    sequences are implemented this should be removed: the operation is not
52    invariant WRT basis so it is not a legit vector computation.
53    
54  proper handling of stabilize method  implicit type promotion of integers to reals where reals are
55    required (e.g. not exponentiation "^")
56    
57  [GLK:2] Save Diderot output to nrrd, instead of "mip.txt"  [GLK:5] Save Diderot output to nrrd, instead of "mip.txt"
58    For grid of strands, save to similarly-shaped array    For grid of strands, save to similarly-shaped array
59    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
60    For ragged things (like tractography output), will need to save both    For ragged things (like tractography output), will need to save both
61      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
62      to index into complete list      to index into complete list
63    
64  [GLK:3] Use of Teem's "hest" command-line parser for getting  [GLK:6] Use of Teem's "hest" command-line parser for getting
65  any input variables that are not defined in the source file  any "input" variables that are not defined in the source file.
66    
67  [GLK:4] ability to declare a field so that probe positions are  [GLK:7] ability to declare a field so that probe positions are
68  *always* "inside"; with various ways of mapping the known image values  *always* "inside"; with various ways of mapping the known image values
69  to non-existant index locations.  One possible syntax emphasizes that  to non-existant index locations.  One possible syntax emphasizes that
70  there is a index mapping function that logically precedes convolution:  there is a index mapping function that logically precedes convolution:
71    F = bspln3 ⊛ (img  clamp)    F = bspln3 ⊛ (img ◦ clamp)
72    F = bspln3 ⊛ (img ◦ repeat)    F = bspln3 ⊛ (img ◦ repeat)
73    F = bspln3 ⊛ (img ◦ mirror)    F = bspln3 ⊛ (img ◦ mirror)
74  where "◦" or "∘" is used to indicate function composition  where "◦" or "∘" is used to indicate function composition
75    
 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).  
   
76  Level of differentiability in field type should be statement about how  Level of differentiability in field type should be statement about how
77  much differentiation the program *needs*, rather than what the kernel  much differentiation the program *needs*, rather than what the kernel
78  *provides*.  The needed differentiability can be less than or equal to  *provides*.  The needed differentiability can be less than or equal to
79  the provided differentiability.  the provided differentiability.
80    
81    Use ∇⊗ etc. syntax
82        syntax [DONE]
83        typechecking
84        IL and codegen
85    
86  Add type aliases for color types  Add type aliases for color types
87      rgb = real{3}      rgb = real{3}
88      rgba = real{4}      rgba = real{4}
# Line 76  Line 95 
95    
96  "initially" supports lists  "initially" supports lists
97    
98  "initially" supports lists of positions output from  "initially" supports lists of positions output from different
99  different initalization Diderot program  initalization Diderot program (or output from the same program;
100    e.g. using output of iso2d.diderot for one isovalue to seed the input
101    to another invocation of the same program)
102    
103  Communication between strands: they have to be able to learn each  Communication between strands: they have to be able to learn each
104  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 115 
115    
116  support for Python interop and GUI  support for Python interop and GUI
117    
118    Allow integer exponentiation ("^2") to apply to square matrices,
119    to represent repeated matrix multiplication
120    
121  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,
122  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.
123  Nearly every Diderot program would be simplified by this.  Nearly every Diderot program would be simplified by this.
# Line 142  Line 166 
166  (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
167  conditional.  conditional.
168    
169  [GLK:5] Want: non-trivial field expressions & functions:  [GLK:8] Want: non-trivial field expressions & functions.
170    scalar fields from scalar fields F and G:
171      field#0(2)[] X = (sin(F) + 1.0)/2;
172      field#0(2)[] X = F*G;
173    scalar field of vector field magnitude:
174    image(2)[2] Vimg = load(...);    image(2)[2] Vimg = load(...);
175    field#0(2)[] Vlen = |Vimg ⊛ bspln3|;    field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
176  to get a scalar field of vector length, or  field of normalized vectors (for LIC and vector field feature extraction)
177      field#2(2)[2] F = ...
178      field#0(2)[2] V = normalize(F);
179    scalar field of gradient magnitude (for edge detection))
180    field#2(2)[] F = Fimg ⊛ bspln3;    field#2(2)[] F = Fimg ⊛ bspln3;
181    field#0(2)[] Gmag = |∇F|;    field#0(2)[] Gmag = |∇F|;
182  to get a scalar field of gradient magnitude, or  scalar field of squared gradient magnitude (simpler to differentiate):
183    field#2(2)[] F = Fimg ⊛ bspln3;    field#2(2)[] F = Fimg ⊛ bspln3;
184    field#0(2)[] Gmsq = ∇F•∇F;    field#0(2)[] Gmsq = ∇F•∇F;
185  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
186  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.  
187    
188  Permit fields composition, especially for warping images by a  Introduce region types (syntax region(d), where d is the dimension of the
189  smooth field of deformation vectors  region.  One useful operator would be
190            dom : field#k(d)[s] -> region(d)
191    Then the inside test could be written as
192            pos ∈ dom(F)
193    We could further extend this approach to allow geometric definitions of
194    regions.  It might also be useful to do inside tests in world space,
195    instead of image space.
196    
197    co- vs contra- index distinction
198    
199    Permit field composition:
200    field#2(3)[3] warp = bspln3 ⊛ warpData;    field#2(3)[3] warp = bspln3 ⊛ warpData;
201    field#2(3)[] F = bspln3 ⊛ img;    field#2(3)[] F = bspln3 ⊛ img;
202    field#2(3)[] Fwarp = F ◦ warp;    field#2(3)[] Fwarp = F ◦ warp;
203  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.
204    This will be instrumental for expressing non-rigid registration
205    methods (but those will require co-vs-contra index distinction)
206    
207  Allow the convolution to be specified either as a single 1D kernel  Allow the convolution to be specified either as a single 1D kernel
208  (as we have it now):  (as we have it now):
209    field#2(3)[] F = bspln3 ⊛ img;    field#2(3)[] F = bspln3 ⊛ img;
210  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.
211    field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;    field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
212  This is especially important for things like time-varying data, or  This is especially important for things like time-varying fields
213  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
214  different from the rest.  What is very unclear is how, in such cases,  must be convolved with a different kernel during probing.
215  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
216  respect to some of the axes.  gradient, when we only want to differentiate with respect to some
217    subset of the axes.  One ambitious idea would be:
218      field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D time-varying field
219      field#0(2)[] F = lambda([x,y], Ft([x,y,42.0]))     // restriction to time=42.0
220      vec2 grad = ∇F([x,y]);                             // 2D gradient
221    
222    Tensors of order 3 (e.g. gradients of diffusion tensor fields, or
223    hessians of vector fields) and order 4 (e.g. Hessians of diffusion
224    tensor fields).
225    
226  co- vs contra- index distinction  representation of tensor symmetry
   
 some indication of tensor symmetry  
227  (have to identify the group of index permutations that are symmetries)  (have to identify the group of index permutations that are symmetries)
228    
229  dot works on all tensors  dot works on all tensors
230    
231  outer works on all tensors  outer works on all tensors
232    
233    Help for debugging Diderot programs: need to be able to uniquely
234    identify strands, and for particular strands that are known to behave
235    badly, do something like printf or other logging of their computations
236    and updates.
237    
238    Permit writing dimensionally general code: Have some statement of the
239    dimension of the world "W" (or have it be learned from one particular
240    field of interest), and then able to write "vec" instead of
241    "vec2/vec3", and perhaps "tensor[W,W]" instead of
242    "tensor[2,2]/tensor[3,3]"
243    
244    Traits: all things things that have boilerplate code (especially
245    volume rendering) should be expressed in terms of the unique
246    computational core.  Different kinds of streamline/tractography
247    computation will be another example, as well as particle systems.
248    
249  Einstein summation notation  Einstein summation notation
250    
251  "tensor comprehension" (like list comprehension)  "tensor comprehension" (like list comprehension)
252    
253    Fields coming from different sources of data:
254    * triangular or tetrahedral meshes over 2D or 3D domains (of the
255      source produced by finite-element codes; these will come with their
256      own specialized kinds of reconstruction kernels, called "basis
257      functions" in this context)
258    * Large point clouds, with some radial basis function around each point,
259      which will be tuned by parameters of the point (at least one parameter
260      giving some notion of radius)
261    
262  ======================  ======================
263  BUGS =================  BUGS =================
264  ======================  ======================

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