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[diderot] Diff of /branches/vis12-cl/TODO
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revision 1121, Thu May 5 08:22:35 2011 UTC revision 1254, Mon May 23 19:40:55 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    
 [GLK:5] run-time death of strands; test/iso2d.diderot provides  
 great initial test for "die" command.  
   
 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
95    
96  "initially" supports lists of positions output from  "initially" supports lists of positions output from different
97  different initalization Diderot program  initalization Diderot program (or output from the same program;
98    e.g. using output of iso2d.diderot for one isovalue to seed the input
99    to another invocation of the same program)
100    
101    Communication between strands: they have to be able to learn each
102    other's state (at the previous iteration).  Early version of this can
103    have the network of neighbors be completely static (for running one
104    strand/pixel image computations).  Later version with strands moving
105    through the domain will require some spatial data structure to
106    optimize discovery of neighbors.
107    
108    ============================
109    MEDIUM-ISH TERM ============ (to make Diderot more useful/effective)
110    ============================
111    
112  spatial data structure that permits strands' queries of neighbors  Python/ctypes interface to run-time
113    
114  proper handling of stabilize method  support for Python interop and GUI
115    
116  test/vr-kcomp2.diderot: Add support for code like  Allow integer exponentiation ("^2") to apply to square matrices,
117    to represent repeated matrix multiplication
118    
119          (F1 if x else F2)@pos  Alow X *= Y, X /= Y, X += Y, X -= Y to mean what they do in C,
120    provided that X*Y, X/Y, X+Y, X-Y are already supported.
121    Nearly every Diderot program would be simplified by this.
122    
123  This will require duplication of the continuation of the conditional  Put small 1-D and 2-D fields, when reconstructed specifically by tent
124  (but we should only duplicate over the live-range of the result of the  and when differentiation is not needed, into faster texture buffers.
125  conditional.  test/illust-vr.diderot is good example of program that uses multiple
126    such 1-D fields basically as lookup-table-based function evaluation
127    
128    expand trace in mid to low translation
129    
130    extend norm (|exp|) to all tensor types [DONE for vectors and matrices]
131    
132    determinant ("det") for tensor[3,3]
133    
134  add ":" for tensor dot product (contracts out two indices  add ":" for tensor dot product (contracts out two indices
135  instead of one like •), valid for all pairs of tensors with  instead of one like •), valid for all pairs of tensors with
136  at least two indices  at least two indices
137    
138  ==============================  test/uninit.diderot:
139  other MEDIUM TERM ============  documents need for better compiler error messages when output variables
140  ==============================  are not initialized; the current messages are very cryptic
141    
142  want: warnings when "D" (reserved for differentiation) is declared as  want: warnings when "D" (reserved for differentiation) is declared as
143  a variable name (get confusing error messages now)  a variable name (get confusing error messages now)
144    
 support for Python interop and GUI  
   
 Python/ctypes interface to run-time  
   
 ==============================  
 LONG TERM ====================  
145  ==============================  ==============================
146    LONG TERM ==================== (make Diderot more interesting/attractive from
147    ==============================  a research standpoint)
148    
149    IL support for higher-order tensor values (matrices, etc).
150        tensor construction [DONE]
151        tensor indexing [DONE]
152        tensor slicing
153        verify that hessians work correctly [DONE]
154    
155  Better handling of variables that determines the scope of a variable  Better handling of variables that determines the scope of a variable
156  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 164  Line 158 
158  scope.  Also prune out useless variables, which should include field  scope.  Also prune out useless variables, which should include field
159  variables after the translation to mid-il.  variables after the translation to mid-il.
160    
161    test/vr-kcomp2.diderot: Add support for code like
162            (F1 if x else F2)@pos
163    This will require duplication of the continuation of the conditional
164    (but we should only duplicate over the live-range of the result of the
165    conditional.
166    
167    [GLK:8] Want: non-trivial field expressions & functions.
168    scalar fields from scalar fields F and G:
169      field#0(2)[] X = (sin(F) + 1.0)/2;
170      field#0(2)[] X = F*G;
171    scalar field of vector field magnitude:
172      image(2)[2] Vimg = load(...);
173      field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
174    field of normalized vectors (for LIC and vector field feature extraction)
175      field#2(2)[2] F = ...
176      field#0(2)[2] V = normalize(F);
177    scalar field of gradient magnitude (for edge detection))
178      field#2(2)[] F = Fimg ⊛ bspln3;
179      field#0(2)[] Gmag = |∇F|;
180    scalar field of squared gradient magnitude (simpler to differentiate):
181      field#2(2)[] F = Fimg ⊛ bspln3;
182      field#0(2)[] Gmsq = ∇F•∇F;
183    There is value in having these, even if the differentiation of them is
184    not supported (hence the indication of "field#0" for these above)
185    
186    Introduce region types (syntax region(d), where d is the dimension of the
187    region.  One useful operator would be
188            dom : field#k(d)[s] -> region(d)
189    Then the inside test could be written as
190            pos ∈ dom(F)
191    We could further extend this approach to allow geometric definitions of
192    regions.  It might also be useful to do inside tests in world space,
193    instead of image space.
194    
195  co- vs contra- index distinction  co- vs contra- index distinction
196    
197  some indication of tensor symmetry  Permit field composition:
198      field#2(3)[3] warp = bspln3 ⊛ warpData;
199      field#2(3)[] F = bspln3 ⊛ img;
200      field#2(3)[] Fwarp = F ◦ warp;
201    So Fwarp(x) = F(warp(X)).  Chain rule can be used for differentation.
202    This will be instrumental for expressing non-rigid registration
203    methods (but those will require co-vs-contra index distinction)
204    
205    Allow the convolution to be specified either as a single 1D kernel
206    (as we have it now):
207      field#2(3)[] F = bspln3 ⊛ img;
208    or, as a tensor product of kernels, one for each axis, e.g.
209      field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
210    This is especially important for things like time-varying fields
211    and the use of scale-space in field visualization: one axis of the
212    must be convolved with a different kernel during probing.
213    What is very unclear is how, in such cases, we should notate the
214    gradient, when we only want to differentiate with respect to some
215    subset of the axes.  One ambitious idea would be:
216      field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D time-varying field
217      field#0(2)[] F = lambda([x,y], Ft([x,y,42.0]))     // restriction to time=42.0
218      vec2 grad = ∇F([x,y]);                             // 2D gradient
219    
220    Tensors of order 3 (e.g. gradients of diffusion tensor fields, or
221    hessians of vector fields) and order 4 (e.g. Hessians of diffusion
222    tensor fields).
223    
224    representation of tensor symmetry
225  (have to identify the group of index permutations that are symmetries)  (have to identify the group of index permutations that are symmetries)
226    
227  dot works on all tensors  dot works on all tensors
228    
229  outer works on all tensors  outer works on all tensors
230    
231    Help for debugging Diderot programs: need to be able to uniquely
232    identify strands, and for particular strands that are known to behave
233    badly, do something like printf or other logging of their computations
234    and updates.
235    
236    Permit writing dimensionally general code: Have some statement of the
237    dimension of the world "W" (or have it be learned from one particular
238    field of interest), and then able to write "vec" instead of
239    "vec2/vec3", and perhaps "tensor[W,W]" instead of
240    "tensor[2,2]/tensor[3,3]"
241    
242    Traits: all things things that have boilerplate code (especially
243    volume rendering) should be expressed in terms of the unique
244    computational core.  Different kinds of streamline/tractography
245    computation will be another example, as well as particle systems.
246    
247  Einstein summation notation  Einstein summation notation
248    
249  "tensor comprehension" (like list comprehension)  "tensor comprehension" (like list comprehension)
250    
251    Fields coming from different sources of data:
252    * triangular or tetrahedral meshes over 2D or 3D domains (of the
253      source produced by finite-element codes; these will come with their
254      own specialized kinds of reconstruction kernels, called "basis
255      functions" in this context)
256    * Large point clouds, with some radial basis function around each point,
257      which will be tuned by parameters of the point (at least one parameter
258      giving some notion of radius)
259    
260  ======================  ======================
261  BUGS =================  BUGS =================
262  ======================  ======================
263    
 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");  
   
264  test/zslice2.diderot:  test/zslice2.diderot:
265  // HEY (bug) bspln5 leads to problems ...  // HEY (bug) bspln5 leads to problems ...
266  //  uncaught exception Size [size]  //  uncaught exception Size [size]

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