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[diderot] Diff of /branches/vis12-cl/TODO
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revision 1133, Thu May 5 18:57:15 2011 UTC revision 1246, Wed May 18 21:27:33 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  ==============================  ========================
   
 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).  
7    
8  Level of differentiability in field type should be statement about how  [GLK:3] Add sequence types (needed for evals & evecs)
 much differentiation the program *needs*, rather than what the kernel  
 *provides*.  The needed differentiability can be less than or equal to  
 the provided differentiability.  
   
 [GLK:1] Add sequence types (needed for evals & evecs)  
9      syntax      syntax
10          types: ty '{' INT '}'          types: ty '{' INT '}'
11          value construction: '{' e1 ',' … ',' en '}'          value construction: '{' e1 ',' … ',' en '}'
12          indexing: e '{' e '}'          indexing: e '{' e '}'
13    
14  IL support for higher-order tensor values (matrices, etc).  [GLK:4] evals & evecs for symmetric tensor[2,2] and
15      tensor construction [DONE]  tensor[3,3] (requires sequences)
     tensor indexing [DONE]  
     tensor slicing  
     verify that hessians work correctly [DONE]  
16    
17  Use ∇⊗ etc. syntax  ability to emit/track/record variables into dynamically re-sized
18      syntax [DONE]  runtime buffer
     typechecking  
     IL and codegen  
19    
20  test/uninit.diderot:  tensor fields: convolution on general tensor images
 documents need for better compiler error messages when output variables  
 are not initialized; the current messages are very cryptic  
21    
22  determinant ("det") for tensor[3,3]  ========================
23    SHORT-ISH TERM ========= (to make using Diderot less annoying to
24    ========================  program in, and slow to execute)
25    
26  expand trace in mid to low translation  value-numbering optimization [DONE]
27    
28  value-numbering optimization  Allow ".ddro" file extensions in addition to ".diderot"
29    
30  Add type aliases for color types  Be able to output values of type tensor[2,2] and tensor[3,3];
31      rgb = real{3}  (currently only scalars & vectors).  Want to add some regression tests
32      rgba = real{4}  based on this and currently can't
33    
34  ==============================  [GLK:1] Add a clamp function, which takes three arguments; either
35  MEDIUM TERM ================== (including needed for streamlines & tractography)  three scalars:
36  ==============================    clamp(lo, hi, x)  = max(lo, min(hi, x))
37    or three vectors of the same size:
38      clamp(lo, hi, [x,y])  = [max(lo[0], min(hi[0], x)),
39                               max(lo[1], min(hi[1], y))]
40    This would be useful in many current Diderot programs.
41    One question: clamp(x, lo, hi) is the argument order used in OpenCL
42    and other places, but clamp(lo, hi, x) is much more consistent with
43    lerp(lo, hi, x), hence GLK's preference
44    
45  [GLK:1] evals & evecs for symmetric tensor[3,3] (requires sequences)  [GLK:2] Proper handling of stabilize method
46    
47  [GLK:2] Save Diderot output to nrrd, instead of "mip.txt"  allow "*" to represent "modulate": per-component multiplication of
48    vectors, and vectors only (not tensors of order 2 or higher).  Once
49    sequences are implemented this should be removed: the operation is not
50    invariant WRT basis so it is not a legit vector computation.
51    
52    implicit type promotion of integers to reals where reals are
53    required (e.g. not exponentiation "^")
54    
55    [GLK:5] Save Diderot output to nrrd, instead of "mip.txt"
56    For grid of strands, save to similarly-shaped array    For grid of strands, save to similarly-shaped array
57    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
58    For ragged things (like tractography output), will need to save both    For ragged things (like tractography output), will need to save both
59      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
60      to index into complete list      to index into complete list
61    
62  [GLK:3] Use of Teem's "hest" command-line parser for getting  [GLK:6] Use of Teem's "hest" command-line parser for getting
63  any input variables that are not defined in the source file  any "input" variables that are not defined in the source file.
64    
65  [GLK:4] ability to declare a field so that probe positions are  [GLK:7] ability to declare a field so that probe positions are
66  *always* "inside"; with various ways of mapping the known image values  *always* "inside"; with various ways of mapping the known image values
67  to non-existant index locations.  One possible syntax emphasizes that  to non-existant index locations.  One possible syntax emphasizes that
68  there is a index mapping function that logically precedes convolution:  there is a index mapping function that logically precedes convolution:
# Line 76  Line 71 
71    F = bspln3 ⊛ (img ◦ mirror)    F = bspln3 ⊛ (img ◦ mirror)
72  where "◦" or "∘" is used to indicate function composition  where "◦" or "∘" is used to indicate function composition
73    
74  extend norm (|exp|) to all tensor types [DONE for vectors and matrices]  Level of differentiability in field type should be statement about how
75    much differentiation the program *needs*, rather than what the kernel
76  ability to emit/track/record variables into dynamically re-sized  *provides*.  The needed differentiability can be less than or equal to
77  runtime buffer  the provided differentiability.
   
 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.  
78    
79  Want: non-trivial field expressions & functions:  Use ∇⊗ etc. syntax
80    image(2)[2] Vimg = load(...);      syntax [DONE]
81    field#0(2)[] Vlen = |Vimg ⊛ bspln3|;      typechecking
82  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.  
83    
84  tensor fields: convolution on general tensor images  Add type aliases for color types
85        rgb = real{3}
86        rgba = real{4}
87    
88  ==============================  ==============================
89  other MEDIUM TERM ============ (needed for particles)  MEDIUM TERM ================== (*needed* for particles)
90  ==============================  ==============================
91    
 Put small 1-D and 2-D fields, when reconstructed specifically by tent  
 and when differentiation is not needed, into faster texture buffers.  
 test/illust-vr.diderot is good example of program that uses multiple  
 such 1-D fields basically as lookup-table-based function evaluation  
   
92  run-time birth of strands  run-time birth of strands
93    
94  "initially" supports lists  "initially" supports lists
# Line 124  Line 96 
96  "initially" supports lists of positions output from  "initially" supports lists of positions output from
97  different initalization Diderot program  different initalization Diderot program
98    
99  spatial data structure that permits strands' queries of neighbors  Communication between strands: they have to be able to learn each
100    other's state (at the previous iteration).  Early version of this can
101    have the network of neighbors be completely static (for running one
102    strand/pixel image computations).  Later version with strands moving
103    through the domain will require some spatial data structure to
104    optimize discovery of neighbors.
105    
106    ============================
107    MEDIUM-ISH TERM ============ (to make Diderot more useful/effective)
108    ============================
109    
110  proper handling of stabilize method  Python/ctypes interface to run-time
111    
112  test/vr-kcomp2.diderot: Add support for code like  support for Python interop and GUI
113    
114          (F1 if x else F2)@pos  Allow integer exponentiation ("^2") to apply to square matrices,
115    to represent repeated matrix multiplication
116    
117  This will require duplication of the continuation of the conditional  Alow X *= Y, X /= Y, X += Y, X -= Y to mean what they do in C,
118  (but we should only duplicate over the live-range of the result of the  provided that X*Y, X/Y, X+Y, X-Y are already supported.
119  conditional.  Nearly every Diderot program would be simplified by this.
120    
121    Put small 1-D and 2-D fields, when reconstructed specifically by tent
122    and when differentiation is not needed, into faster texture buffers.
123    test/illust-vr.diderot is good example of program that uses multiple
124    such 1-D fields basically as lookup-table-based function evaluation
125    
126    expand trace in mid to low translation
127    
128    extend norm (|exp|) to all tensor types [DONE for vectors and matrices]
129    
130    determinant ("det") for tensor[3,3]
131    
132  add ":" for tensor dot product (contracts out two indices  add ":" for tensor dot product (contracts out two indices
133  instead of one like •), valid for all pairs of tensors with  instead of one like •), valid for all pairs of tensors with
134  at least two indices  at least two indices
135    
136  ==============================  test/uninit.diderot:
137  other MEDIUM TERM ============  documents need for better compiler error messages when output variables
138  ==============================  are not initialized; the current messages are very cryptic
139    
140  want: warnings when "D" (reserved for differentiation) is declared as  want: warnings when "D" (reserved for differentiation) is declared as
141  a variable name (get confusing error messages now)  a variable name (get confusing error messages now)
142    
 support for Python interop and GUI  
   
 Python/ctypes interface to run-time  
   
 ==============================  
 LONG TERM ====================  
143  ==============================  ==============================
144    LONG TERM ==================== (make Diderot more interesting/attractive from
145    ==============================  a research standpoint)
146    
147    IL support for higher-order tensor values (matrices, etc).
148        tensor construction [DONE]
149        tensor indexing [DONE]
150        tensor slicing
151        verify that hessians work correctly [DONE]
152    
153  Better handling of variables that determines the scope of a variable  Better handling of variables that determines the scope of a variable
154  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 161  Line 156 
156  scope.  Also prune out useless variables, which should include field  scope.  Also prune out useless variables, which should include field
157  variables after the translation to mid-il.  variables after the translation to mid-il.
158    
159    test/vr-kcomp2.diderot: Add support for code like
160            (F1 if x else F2)@pos
161    This will require duplication of the continuation of the conditional
162    (but we should only duplicate over the live-range of the result of the
163    conditional.
164    
165    [GLK:8] Want: non-trivial field expressions & functions.
166    scalar fields from scalar fields F and G:
167      field#0(2)[] X = (sin(F) + 1.0)/2;
168      field#0(2)[] X = F*G;
169    scalar field of vector field magnitude:
170      image(2)[2] Vimg = load(...);
171      field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
172    field of normalized vectors (for LIC and vector field feature extraction)
173      field#2(2)[2] F = ...
174      field#0(2)[2] V = normalize(F);
175    scalar field of gradient magnitude (for edge detection))
176      field#2(2)[] F = Fimg ⊛ bspln3;
177      field#0(2)[] Gmag = |∇F|;
178    scalar field of squared gradient magnitude (simpler to differentiate):
179      field#2(2)[] F = Fimg ⊛ bspln3;
180      field#0(2)[] Gmsq = ∇F•∇F;
181    There is value in having these, even if the differentiation of them is
182    not supported (hence the indication of "field#0" for these above)
183    
184    Introduce region types (syntax region(d), where d is the dimension of the
185    region.  One useful operator would be
186            dom : field#k(d)[s] -> region(d)
187    Then the inside test could be written as
188            pos ∈ dom(F)
189    We could further extend this approach to allow geometric definitions of
190    regions.  It might also be useful to do inside tests in world space,
191    instead of image space.
192    
193  co- vs contra- index distinction  co- vs contra- index distinction
194    
195  some indication of tensor symmetry  Permit field composition:
196      field#2(3)[3] warp = bspln3 ⊛ warpData;
197      field#2(3)[] F = bspln3 ⊛ img;
198      field#2(3)[] Fwarp = F ◦ warp;
199    So Fwarp(x) = F(warp(X)).  Chain rule can be used for differentation.
200    This will be instrumental for expressing non-rigid registration
201    methods (but those will require co-vs-contra index distinction)
202    
203    Allow the convolution to be specified either as a single 1D kernel
204    (as we have it now):
205      field#2(3)[] F = bspln3 ⊛ img;
206    or, as a tensor product of kernels, one for each axis, e.g.
207      field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
208    This is especially important for things like time-varying fields
209    and the use of scale-space in field visualization: one axis of the
210    must be convolved with a different kernel during probing.
211    What is very unclear is how, in such cases, we should notate the
212    gradient, when we only want to differentiate with respect to some
213    subset of the axes.  One ambitious idea would be:
214      field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D time-varying field
215      field#0(2)[] F = lambda([x,y], Ft([x,y,42.0]))     // restriction to time=42.0
216      vec2 grad = ∇F([x,y]);                             // 2D gradient
217    
218    Tensors of order 3 (e.g. gradients of diffusion tensor fields, or
219    hessians of vector fields) and order 4 (e.g. Hessians of diffusion
220    tensor fields).
221    
222    representation of tensor symmetry
223  (have to identify the group of index permutations that are symmetries)  (have to identify the group of index permutations that are symmetries)
224    
225  dot works on all tensors  dot works on all tensors
226    
227  outer works on all tensors  outer works on all tensors
228    
229    Help for debugging Diderot programs: need to be able to uniquely
230    identify strands, and for particular strands that are known to behave
231    badly, do something like printf or other logging of their computations
232    and updates.
233    
234    Permit writing dimensionally general code: Have some statement of the
235    dimension of the world "W" (or have it be learned from one particular
236    field of interest), and then able to write "vec" instead of
237    "vec2/vec3", and perhaps "tensor[W,W]" instead of
238    "tensor[2,2]/tensor[3,3]"
239    
240    Traits: all things things that have boilerplate code (especially
241    volume rendering) should be expressed in terms of the unique
242    computational core.  Different kinds of streamline/tractography
243    computation will be another example, as well as particle systems.
244    
245  Einstein summation notation  Einstein summation notation
246    
247  "tensor comprehension" (like list comprehension)  "tensor comprehension" (like list comprehension)
248    
249    Fields coming from different sources of data:
250    * triangular or tetrahedral meshes over 2D or 3D domains (of the
251      source produced by finite-element codes; these will come with their
252      own specialized kinds of reconstruction kernels, called "basis
253      functions" in this context)
254    * Large point clouds, with some radial basis function around each point,
255      which will be tuned by parameters of the point (at least one parameter
256      giving some notion of radius)
257    
258  ======================  ======================
259  BUGS =================  BUGS =================
260  ======================  ======================
261    
 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");  
   
262  test/zslice2.diderot:  test/zslice2.diderot:
263  // HEY (bug) bspln5 leads to problems ...  // HEY (bug) bspln5 leads to problems ...
264  //  uncaught exception Size [size]  //  uncaught exception Size [size]

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