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:2] 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:3] evals & evecs for symmetric tensor[2,2] and 
17 

tensor[3,3] (requires sequences) 
18 


19 
ability to emit/track/record variables into dynamically resized 
ability to emit/track/record variables into dynamically resized 
20 
runtime buffer 
runtime buffer 
22 
tensor fields: convolution on general tensor images 
tensor fields: convolution on general tensor images 
23 


24 
======================== 
======================== 
25 
SHORTISH TERM ========= (to make using Diderot less annoying/slow) 
SHORTISH TERM ========= (to make using Diderot less annoying to 
26 
======================== 
======================== program in, and slow to execute) 
27 


28 

valuenumbering 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] Proper handling of stabilize method 
37 


38 
valuenumbering optimization 
allow "*" to represent "modulate": percomponent 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 
proper handling of stabilize method 
implicit type promotion of integers to reals where reals are 
44 

required (e.g. not exponentiation "^") 
45 


46 
[GLK:2] Save Diderot output to nrrd, instead of "mip.txt" 
[GLK:4] Save Diderot output to nrrd, instead of "mip.txt" 
47 
For grid of strands, save to similarlyshaped array 
For grid of strands, save to similarlyshaped array 
48 
For list of strands, save to long 1D (or 2D for nonscalar output) list 
For list of strands, save to long 1D (or 2D for nonscalar 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" commandline parser for getting 
[GLK:5] Use of Teem's "hest" commandline parser for getting 
54 
any input variables that are not defined in the source file 
any "input" variables that are not defined in the source file. 
55 


56 
[GLK:4] ability to declare a field so that probe positions are 
[GLK:6] ability to declare a field so that probe positions are 
57 
*always* "inside"; with various ways of mapping the known image values 
*always* "inside"; with various ways of mapping the known image values 
58 
to nonexistant index locations. One possible syntax emphasizes that 
to nonexistant index locations. One possible syntax emphasizes that 
59 
there is a index mapping function that logically precedes convolution: 
there is a index mapping function that logically precedes convolution: 
60 
F = bspln3 ⊛ (img clamp) 
F = bspln3 ⊛ (img ◦ clamp) 
61 
F = bspln3 ⊛ (img ◦ repeat) 
F = bspln3 ⊛ (img ◦ repeat) 
62 
F = bspln3 ⊛ (img ◦ mirror) 
F = bspln3 ⊛ (img ◦ mirror) 
63 
where "◦" or "∘" is used to indicate function composition 
where "◦" or "∘" is used to indicate function composition 
64 



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). 




65 
Level of differentiability in field type should be statement about how 
Level of differentiability in field type should be statement about how 
66 
much differentiation the program *needs*, rather than what the kernel 
much differentiation the program *needs*, rather than what the kernel 
67 
*provides*. The needed differentiability can be less than or equal to 
*provides*. The needed differentiability can be less than or equal to 
68 
the provided differentiability. 
the provided differentiability. 
69 


70 

Use ∇⊗ etc. syntax 
71 

syntax [DONE] 
72 

typechecking 
73 

IL and codegen 
74 


75 
Add type aliases for color types 
Add type aliases for color types 
76 
rgb = real{3} 
rgb = real{3} 
77 
rgba = real{4} 
rgba = real{4} 
84 


85 
"initially" supports lists 
"initially" supports lists 
86 


87 
"initially" supports lists of positions output from 
"initially" supports lists of positions output from different 
88 
different initalization Diderot program 
initalization Diderot program (or output from the same program; 
89 

e.g. using output of iso2d.diderot for one isovalue to seed the input 
90 

to another invocation of the same program) 
91 


92 
Communication between strands: they have to be able to learn each 
Communication between strands: they have to be able to learn each 
93 
other's state (at the previous iteration). Early version of this can 
other's state (at the previous iteration). Early version of this can 
104 


105 
support for Python interop and GUI 
support for Python interop and GUI 
106 


107 
Alow X *= Y, X /= Y, X += Y, X = Y to mean what they do in C, 
Allow integer exponentiation ("^2") to apply to square matrices, 
108 
provided that X*Y, X/Y, X+Y, XY are already supported. 
to represent repeated matrix multiplication 

Nearly every Diderot program would be simplified by this. 

109 


110 
Put small 1D and 2D fields, when reconstructed specifically by tent 
Put small 1D and 2D fields, when reconstructed specifically by tent 
111 
and when differentiation is not needed, into faster texture buffers. 
and when differentiation is not needed, into faster texture buffers. 
112 
test/illustvr.diderot is good example of program that uses multiple 
test/illustvr.diderot is good example of program that uses multiple 
113 
such 1D fields basically as lookuptablebased function evaluation 
such 1D fields basically as lookuptablebased function evaluation 
114 


115 
expand trace in mid to low translation 
expand trace in mid to low translation [DONE] 
116 


117 
extend norm (exp) to all tensor types [DONE for vectors and matrices] 
extend norm (exp) to all tensor types [DONE for vectors and matrices] 
118 


151 
(but we should only duplicate over the liverange of the result of the 
(but we should only duplicate over the liverange of the result of the 
152 
conditional. 
conditional. 
153 


154 
[GLK:5] Want: nontrivial field expressions & functions: 
[GLK:7] Want: nontrivial field expressions & functions. 
155 

scalar fields from scalar fields F and G: 
156 

field#0(2)[] X = (sin(F) + 1.0)/2; 
157 

field#0(2)[] X = F*G; 
158 

scalar field of vector field magnitude: 
159 
image(2)[2] Vimg = load(...); 
image(2)[2] Vimg = load(...); 
160 
field#0(2)[] Vlen = Vimg ⊛ bspln3; 
field#0(2)[] Vlen = Vimg ⊛ bspln3; 
161 
to get a scalar field of vector length, or 
field of normalized vectors (for LIC and vector field feature extraction) 
162 

field#2(2)[2] F = ... 
163 

field#0(2)[2] V = normalize(F); 
164 

scalar field of gradient magnitude (for edge detection)) 
165 
field#2(2)[] F = Fimg ⊛ bspln3; 
field#2(2)[] F = Fimg ⊛ bspln3; 
166 
field#0(2)[] Gmag = ∇F; 
field#0(2)[] Gmag = ∇F; 
167 
to get a scalar field of gradient magnitude, or 
scalar field of squared gradient magnitude (simpler to differentiate): 
168 
field#2(2)[] F = Fimg ⊛ bspln3; 
field#2(2)[] F = Fimg ⊛ bspln3; 
169 
field#0(2)[] Gmsq = ∇F•∇F; 
field#0(2)[] Gmsq = ∇F•∇F; 
170 
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 
171 
to differentiate. However, there is value in having these, even if 
not supported (hence the indication of "field#0" for these above) 
172 
the differentiation of them is not supported (hence the indication 

173 
of "field#0" for these above) 
Introduce region types (syntax region(d), where d is the dimension of the 
174 

region. One useful operator would be 
175 
Want: ability to apply "normalize" to a field itself, e.g. 
dom : field#k(d)[s] > region(d) 
176 
field#0(2)[2] V = normalize(Vimg ⊛ ctmr); 
Then the inside test could be written as 
177 
so that V(x) = normalize((Vimg ⊛ ctmr)(x)). 
pos ∈ dom(F) 
178 
Having this would simplify expression of standard LIC method, and 
We could further extend this approach to allow geometric definitions of 
179 
would also help express other vector field expressions that arise 
regions. It might also be useful to do inside tests in world space, 
180 
in vector field feature exraction. 
instead of image space. 
181 


182 
Permit fields composition, especially for warping images by a 
co vs contra index distinction 
183 
smooth field of deformation vectors 

184 

Permit field composition: 
185 
field#2(3)[3] warp = bspln3 ⊛ warpData; 
field#2(3)[3] warp = bspln3 ⊛ warpData; 
186 
field#2(3)[] F = bspln3 ⊛ img; 
field#2(3)[] F = bspln3 ⊛ img; 
187 
field#2(3)[] Fwarp = F ◦ warp; 
field#2(3)[] Fwarp = F ◦ warp; 
188 
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. 
189 

This will be instrumental for expressing nonrigid registration 
190 

methods (but those will require covscontra index distinction) 
191 


192 
Allow the convolution to be specified either as a single 1D kernel 
Allow the convolution to be specified either as a single 1D kernel 
193 
(as we have it now): 
(as we have it now): 
194 
field#2(3)[] F = bspln3 ⊛ img; 
field#2(3)[] F = bspln3 ⊛ img; 
195 
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. 
196 
field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; 
field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; 
197 
This is especially important for things like timevarying data, or 
This is especially important for things like timevarying fields 
198 
other multidimensional fields where one axis of the domain is very 
and the use of scalespace in field visualization: one axis of the 
199 
different from the rest. What is very unclear is how, in such cases, 
must be convolved with a different kernel during probing. 
200 
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 
201 
respect to some of the axes. 
gradient, when we only want to differentiate with respect to some 
202 

subset of the axes. One ambitious idea would be: 
203 
co vs contra index distinction 
field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D timevarying field 
204 

field#0(2)[] F = lambda([x,y], Ft([x,y,42.0])) // restriction to time=42.0 
205 

vec2 grad = ∇F([x,y]); // 2D gradient 
206 


207 

Tensors of order 3 (e.g. gradients of diffusion tensor fields, or 
208 

hessians of vector fields) and order 4 (e.g. Hessians of diffusion 
209 

tensor fields). 
210 


211 
some indication of tensor symmetry 
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 finiteelement 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 
====================== 
====================== 
253 
// uncaught exception Size [size] 
// uncaught exception Size [size] 
254 
// raised at ctarget/ctarget.sml:47.1547.19 
// raised at ctarget/ctarget.sml:47.1547.19 
255 
//field#4(3)[] F = img ⊛ bspln5; 
//field#4(3)[] F = img ⊛ bspln5; 
256 

