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revision 1121, Thu May 5 08:22:35 2011 UTC revision 1442, Sun Jul 10 08:09:50 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  ==============================  ========================
7    
8  Add a clamp function, which takes three arguments; either three scalars:  [GLK:2] Add sequence types (needed for evals & evecs)
   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).  
   
 Level of differentiability in field type should be statement about how  
 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:3] 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 output buffer
     typechecking  
     IL and codegen  
19    
20  test/uninit.diderot:  [GLK:4] tensor fields from tensor images: Initially need at least
21  documents need for better compiler error messages when output variables  convolution on tensor[2,2] and tensor[3,3] (the same component-wise
22  are not initialized; the current messages are very cryptic  convolution as for vectors).
23    
24  determinant ("det") for tensor[3,3]  ========================
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  Allow ".ddro" file extensions in addition to ".diderot"
29    
30  value-numbering optimization  Be able to output values of type tensor[2,2] and tensor[3,3];
31    (currently only scalars & vectors).  Want to add some regression tests
32    based on this and currently can't
33    
34  Add type aliases for color types  [GLK:1] Proper handling of stabilize method
     rgb = real{3}  
     rgba = real{4}  
35    
36  ==============================  Convolution on general tensor images (order > 2)
 MEDIUM TERM ================== (including needed for streamlines & tractography)  
 ==============================  
37    
38  [GLK:1] evals & evecs for symmetric tensor[3,3] (requires sequences)  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  [GLK:2] Save Diderot output to nrrd, instead of "mip.txt"  implicit type promotion of integers to reals where reals are
44    required (e.g. not exponentiation "^")
45    
46    [Nick working on this] Save Diderot output to nrrd, instead of "mip.txt"
47    For grid of strands, save to similarly-shaped array    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    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    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      complete list of values, as well as list of start indices and lengths
51      to index into complete list      to index into complete list
52    
53  [GLK:3] Use of Teem's "hest" command-line parser for getting  [GLK:6] ability to declare a field so that probe positions are
 any input variables that are not defined in the source file  
   
 [GLK:4] ability to declare a field so that probe positions are  
54  *always* "inside"; with various ways of mapping the known image values  *always* "inside"; with various ways of mapping the known image values
55  to non-existant index locations.  One possible syntax emphasizes that  to non-existant index locations.  One possible syntax emphasizes that
56  there is a index mapping function that logically precedes convolution:  there is a index mapping function that logically precedes convolution:
# Line 76  Line 59 
59    F = bspln3 ⊛ (img ◦ mirror)    F = bspln3 ⊛ (img ◦ mirror)
60  where "◦" or "∘" is used to indicate function composition  where "◦" or "∘" is used to indicate function composition
61    
62  extend norm (|exp|) to all tensor types [DONE for vectors and matrices]  Level of differentiability in field type should be statement about how
63    much differentiation the program *needs*, rather than what the kernel
64  ability to emit/track/record variables into dynamically re-sized  *provides*.  The needed differentiability can be less than or equal to
65  runtime buffer  the provided differentiability.
66    
67  Want: allow X *= Y, X /= Y, X += Y, X -= Y to mean what they do in C,  Use ∇⊗ etc. syntax
68  provided that X*Y, X/Y, X+Y, X-Y are already supported.      syntax [DONE]
69  Nearly every Diderot program would be simplified by this.      typechecking
70        IL and codegen
71    
72  Want: non-trivial field expressions & functions:  Add type aliases for color types
73    image(2)[2] Vimg = load(...);      rgb = real{3}
74    field#0(2)[] Vlen = |Vimg ⊛ bspln3|;      rgba = real{4}
 to get a scalar field of vector length, or  
   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.  
75    
76  tensor fields: convolution on general tensor images  Revisit how images are created within the language.
77    The "load" operator should probably go away, and its strangs
78    that strings are there only as a way to refer to nrrd filenames
79    
80  ==============================  ==============================
81  other MEDIUM TERM ============ (needed for particles)  MEDIUM TERM ================== (*needed* for particles)
82  ==============================  ==============================
83    
84  [GLK:5] run-time death of strands; test/iso2d.diderot provides  [Lamont working on this] run-time birth of strands
 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  
   
 run-time birth of strands  
85    
86  "initially" supports lists  "initially" supports lists
87    
88  "initially" supports lists of positions output from  "initially" supports lists of positions output from different
89  different initalization Diderot program  initalization Diderot program (or output from the same program;
90    e.g. using output of iso2d.diderot for one isovalue to seed the input
91    to another invocation of the same program)
92    
93    [Lamont working on this] Communication between strands: they have to
94    be able to learn each other's state (at the previous iteration).
95    Early version of this can have the network of neighbors be completely
96    static (for running one strand/pixel image computations).  Later
97    version with strands moving through the domain will require some
98    spatial data structure to optimize discovery of neighbors.
99    
100    ============================
101    MEDIUM-ISH TERM ============ (to make Diderot more useful/effective)
102    ============================
103    
104    [GLK:5] Want code-generation working for tensors of order three.
105    Order three matters for edge detection in scalar fields (to get
106    second derivatives of gradient magnitude), second derivatives
107    of vector fields (for some feature extraction), and first
108    derivatives of diffusion tensor fields.
109    
110  spatial data structure that permits strands' queries of neighbors  Python/ctypes interface to run-time
111    
112  proper handling of stabilize method  support for Python interop and GUI
113    
114  test/vr-kcomp2.diderot: Add support for code like  Allow integer exponentiation ("^2") to apply to square matrices,
115    to represent repeated matrix multiplication
116    
117          (F1 if x else F2)@pos  Put small 1-D and 2-D fields, when reconstructed specifically by tent
118    and when differentiation is not needed, into faster texture buffers.
119    test/illust-vr.diderot is good example of program that uses multiple
120    such 1-D fields basically as lookup-table-based function evaluation
121    
122  This will require duplication of the continuation of the conditional  extend norm (|exp|) to all tensor types [DONE for vectors and matrices]
123  (but we should only duplicate over the live-range of the result of the  
124  conditional.  determinant ("det") for tensor[3,3]
125    
126  add ":" for tensor dot product (contracts out two indices  add ":" for tensor dot product (contracts out two indices
127  instead of one like •), valid for all pairs of tensors with  instead of one like •), valid for all pairs of tensors with
128  at least two indices  at least two indices
129    
130  ==============================  test/uninit.diderot:
131  other MEDIUM TERM ============  documents need for better compiler error messages when output variables
132  ==============================  are not initialized; the current messages are very cryptic
133    
134  want: warnings when "D" (reserved for differentiation) is declared as  want: warnings when "D" (reserved for differentiation) is declared as
135  a variable name (get confusing error messages now)  a variable name (get confusing error messages now)
136    
 support for Python interop and GUI  
   
 Python/ctypes interface to run-time  
   
 ==============================  
 LONG TERM ====================  
137  ==============================  ==============================
138    LONG TERM ==================== (make Diderot more interesting/attractive from
139    ==============================  a research standpoint)
140    
141    IL support for higher-order tensor values (matrices, etc).
142        tensor construction [DONE]
143        tensor indexing [DONE]
144        tensor slicing
145    
146  Better handling of variables that determines the scope of a variable  Better handling of variables that determines the scope of a variable
147  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 149 
149  scope.  Also prune out useless variables, which should include field  scope.  Also prune out useless variables, which should include field
150  variables after the translation to mid-il.  variables after the translation to mid-il.
151    
152    test/vr-kcomp2.diderot: Add support for code like
153            (F1 if x else F2)@pos
154    This will require duplication of the continuation of the conditional
155    (but we should only duplicate over the live-range of the result of the
156    conditional.
157    
158    [GLK:7] Want: non-trivial field expressions & functions.
159    scalar fields from scalar fields F and G:
160      field#0(2)[] X = (sin(F) + 1.0)/2;
161      field#0(2)[] X = F*G;
162    scalar field of vector field magnitude:
163      image(2)[2] Vimg = load(...);
164      field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
165    field of normalized vectors (for LIC and vector field feature extraction)
166      field#2(2)[2] F = ...
167      field#0(2)[2] V = normalize(F);
168    scalar field of gradient magnitude (for edge detection))
169      field#2(2)[] F = Fimg ⊛ bspln3;
170      field#0(2)[] Gmag = |∇F|;
171    scalar field of squared gradient magnitude (simpler to differentiate):
172      field#2(2)[] F = Fimg ⊛ bspln3;
173      field#0(2)[] Gmsq = ∇F•∇F;
174    There is value in having these, even if the differentiation of them is
175    not supported (hence the indication of "field#0" for these above)
176    
177    Introduce region types (syntax region(d), where d is the dimension of the
178    region.  One useful operator would be
179            dom : field#k(d)[s] -> region(d)
180    Then the inside test could be written as
181            pos ∈ dom(F)
182    We could further extend this approach to allow geometric definitions of
183    regions.  It might also be useful to do inside tests in world space,
184    instead of image space.
185    
186  co- vs contra- index distinction  co- vs contra- index distinction
187    
188  some indication of tensor symmetry  Permit field composition:
189      field#2(3)[3] warp = bspln3 ⊛ warpData;
190      field#2(3)[] F = bspln3 ⊛ img;
191      field#2(3)[] Fwarp = F ◦ warp;
192    So Fwarp(x) = F(warp(X)).  Chain rule can be used for differentation.
193    This will be instrumental for expressing non-rigid registration
194    methods (but those will require co-vs-contra index distinction)
195    
196    Allow the convolution to be specified either as a single 1D kernel
197    (as we have it now):
198      field#2(3)[] F = bspln3 ⊛ img;
199    or, as a tensor product of kernels, one for each axis, e.g.
200      field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
201    This is especially important for things like time-varying fields
202    and the use of scale-space in field visualization: one axis of the
203    must be convolved with a different kernel during probing.
204    What is very unclear is how, in such cases, we should notate the
205    gradient, when we only want to differentiate with respect to some
206    subset of the axes.  One ambitious idea would be:
207      field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D time-varying field
208      field#0(2)[] F = lambda([x,y], Ft([x,y,42.0]))     // restriction to time=42.0
209      vec2 grad = ∇F([x,y]);                             // 2D gradient
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 =================  BUGS =================
249  ======================  ======================
250    
 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");  
   
251  test/zslice2.diderot:  test/zslice2.diderot:
252  // HEY (bug) bspln5 leads to problems ...  // HEY (bug) bspln5 leads to problems ...
253  //  uncaught exception Size [size]  //  uncaught exception Size [size]
254  //    raised at c-target/c-target.sml:47.15-47.19  //    raised at c-target/c-target.sml:47.15-47.19
255  //field#4(3)[] F = img ⊛ bspln5;  //field#4(3)[] F = img ⊛ bspln5;
256    

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