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 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 
valuenumbering optimization 
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 

[DONE] 
47 


48 

[GLK:2] Proper handling of stabilize method 
49 


50 

allow "*" to represent "modulate": percomponent multiplication of 
51 

vectors, and vectors only (not tensors of order 2 or higher). Once 
52 

sequences are implemented this should be removed: the operation is not 
53 

invariant WRT basis so it is not a legit vector computation. 
54 


55 
proper handling of stabilize method 
implicit type promotion of integers to reals where reals are 
56 

required (e.g. not exponentiation "^") 
57 


58 
[GLK:2] Save Diderot output to nrrd, instead of "mip.txt" 
[GLK:5] Save Diderot output to nrrd, instead of "mip.txt" 
59 
For grid of strands, save to similarlyshaped array 
For grid of strands, save to similarlyshaped array 
60 
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 
61 
For ragged things (like tractography output), will need to save both 
For ragged things (like tractography output), will need to save both 
62 
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 
63 
to index into complete list 
to index into complete list 
64 


65 
[GLK:3] Use of Teem's "hest" commandline parser for getting 
[GLK:6] Use of Teem's "hest" commandline parser for getting 
66 
any input variables that are not defined in the source file 
any "input" variables that are not defined in the source file. 
67 


68 
[GLK:4] ability to declare a field so that probe positions are 
[GLK:7] ability to declare a field so that probe positions are 
69 
*always* "inside"; with various ways of mapping the known image values 
*always* "inside"; with various ways of mapping the known image values 
70 
to nonexistant index locations. One possible syntax emphasizes that 
to nonexistant index locations. One possible syntax emphasizes that 
71 
there is a index mapping function that logically precedes convolution: 
there is a index mapping function that logically precedes convolution: 
72 
F = bspln3 ⊛ (img clamp) 
F = bspln3 ⊛ (img ◦ clamp) 
73 
F = bspln3 ⊛ (img ◦ repeat) 
F = bspln3 ⊛ (img ◦ repeat) 
74 
F = bspln3 ⊛ (img ◦ mirror) 
F = bspln3 ⊛ (img ◦ mirror) 
75 
where "◦" or "∘" is used to indicate function composition 
where "◦" or "∘" is used to indicate function composition 
76 



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). 




77 
Level of differentiability in field type should be statement about how 
Level of differentiability in field type should be statement about how 
78 
much differentiation the program *needs*, rather than what the kernel 
much differentiation the program *needs*, rather than what the kernel 
79 
*provides*. The needed differentiability can be less than or equal to 
*provides*. The needed differentiability can be less than or equal to 
80 
the provided differentiability. 
the provided differentiability. 
81 


82 

Use ∇⊗ etc. syntax 
83 

syntax [DONE] 
84 

typechecking 
85 

IL and codegen 
86 


87 
Add type aliases for color types 
Add type aliases for color types 
88 
rgb = real{3} 
rgb = real{3} 
89 
rgba = real{4} 
rgba = real{4} 
96 


97 
"initially" supports lists 
"initially" supports lists 
98 


99 
"initially" supports lists of positions output from 
"initially" supports lists of positions output from different 
100 
different initalization Diderot program 
initalization Diderot program (or output from the same program; 
101 

e.g. using output of iso2d.diderot for one isovalue to seed the input 
102 

to another invocation of the same program) 
103 


104 
Communication between strands: they have to be able to learn each 
Communication between strands: they have to be able to learn each 
105 
other's state (at the previous iteration). Early version of this can 
other's state (at the previous iteration). Early version of this can 
116 


117 
support for Python interop and GUI 
support for Python interop and GUI 
118 


119 

Allow integer exponentiation ("^2") to apply to square matrices, 
120 

to represent repeated matrix multiplication 
121 


122 
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, 
123 
provided that X*Y, X/Y, X+Y, XY are already supported. 
provided that X*Y, X/Y, X+Y, XY are already supported. 
124 
Nearly every Diderot program would be simplified by this. 
Nearly every Diderot program would be simplified by this. 
167 
(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 
168 
conditional. 
conditional. 
169 


170 
[GLK:5] Want: nontrivial field expressions & functions: 
[GLK:8] Want: nontrivial field expressions & functions. 
171 

scalar fields from scalar fields F and G: 
172 

field#0(2)[] X = (sin(F) + 1.0)/2; 
173 

field#0(2)[] X = F*G; 
174 

scalar field of vector field magnitude: 
175 
image(2)[2] Vimg = load(...); 
image(2)[2] Vimg = load(...); 
176 
field#0(2)[] Vlen = Vimg ⊛ bspln3; 
field#0(2)[] Vlen = Vimg ⊛ bspln3; 
177 
to get a scalar field of vector length, or 
field of normalized vectors (for LIC and vector field feature extraction) 
178 

field#2(2)[2] F = ... 
179 

field#0(2)[2] V = normalize(F); 
180 

scalar field of gradient magnitude (for edge detection)) 
181 
field#2(2)[] F = Fimg ⊛ bspln3; 
field#2(2)[] F = Fimg ⊛ bspln3; 
182 
field#0(2)[] Gmag = ∇F; 
field#0(2)[] Gmag = ∇F; 
183 
to get a scalar field of gradient magnitude, or 
scalar field of squared gradient magnitude (simpler to differentiate): 
184 
field#2(2)[] F = Fimg ⊛ bspln3; 
field#2(2)[] F = Fimg ⊛ bspln3; 
185 
field#0(2)[] Gmsq = ∇F•∇F; 
field#0(2)[] Gmsq = ∇F•∇F; 
186 
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 
187 
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. 

188 


189 
Permit fields composition, especially for warping images by a 
Introduce region types (syntax region(d), where d is the dimension of the 
190 
smooth field of deformation vectors 
region. One useful operator would be 
191 

dom : field#k(d)[s] > region(d) 
192 

Then the inside test could be written as 
193 

pos ∈ dom(F) 
194 

We could further extend this approach to allow geometric definitions of 
195 

regions. It might also be useful to do inside tests in world space, 
196 

instead of image space. 
197 


198 

co vs contra index distinction 
199 


200 

Permit field composition: 
201 
field#2(3)[3] warp = bspln3 ⊛ warpData; 
field#2(3)[3] warp = bspln3 ⊛ warpData; 
202 
field#2(3)[] F = bspln3 ⊛ img; 
field#2(3)[] F = bspln3 ⊛ img; 
203 
field#2(3)[] Fwarp = F ◦ warp; 
field#2(3)[] Fwarp = F ◦ warp; 
204 
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. 
205 

This will be instrumental for expressing nonrigid registration 
206 

methods (but those will require covscontra index distinction) 
207 


208 
Allow the convolution to be specified either as a single 1D kernel 
Allow the convolution to be specified either as a single 1D kernel 
209 
(as we have it now): 
(as we have it now): 
210 
field#2(3)[] F = bspln3 ⊛ img; 
field#2(3)[] F = bspln3 ⊛ img; 
211 
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. 
212 
field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; 
field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; 
213 
This is especially important for things like timevarying data, or 
This is especially important for things like timevarying fields 
214 
other multidimensional fields where one axis of the domain is very 
and the use of scalespace in field visualization: one axis of the 
215 
different from the rest. What is very unclear is how, in such cases, 
must be convolved with a different kernel during probing. 
216 
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 
217 
respect to some of the axes. 
gradient, when we only want to differentiate with respect to some 
218 

subset of the axes. One ambitious idea would be: 
219 

field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D timevarying field 
220 

field#0(2)[] F = lambda([x,y], Ft([x,y,42.0])) // restriction to time=42.0 
221 

vec2 grad = ∇F([x,y]); // 2D gradient 
222 


223 

Tensors of order 3 (e.g. gradients of diffusion tensor fields, or 
224 

hessians of vector fields) and order 4 (e.g. Hessians of diffusion 
225 

tensor fields). 
226 


227 
co vs contra index distinction 
representation of tensor symmetry 




some indication of tensor symmetry 

228 
(have to identify the group of index permutations that are symmetries) 
(have to identify the group of index permutations that are symmetries) 
229 


230 
dot works on all tensors 
dot works on all tensors 
231 


232 
outer works on all tensors 
outer works on all tensors 
233 


234 

Help for debugging Diderot programs: need to be able to uniquely 
235 

identify strands, and for particular strands that are known to behave 
236 

badly, do something like printf or other logging of their computations 
237 

and updates. 
238 


239 

Permit writing dimensionally general code: Have some statement of the 
240 

dimension of the world "W" (or have it be learned from one particular 
241 

field of interest), and then able to write "vec" instead of 
242 

"vec2/vec3", and perhaps "tensor[W,W]" instead of 
243 

"tensor[2,2]/tensor[3,3]" 
244 


245 

Traits: all things things that have boilerplate code (especially 
246 

volume rendering) should be expressed in terms of the unique 
247 

computational core. Different kinds of streamline/tractography 
248 

computation will be another example, as well as particle systems. 
249 


250 
Einstein summation notation 
Einstein summation notation 
251 


252 
"tensor comprehension" (like list comprehension) 
"tensor comprehension" (like list comprehension) 
253 


254 

Fields coming from different sources of data: 
255 

* triangular or tetrahedral meshes over 2D or 3D domains (of the 
256 

source produced by finiteelement codes; these will come with their 
257 

own specialized kinds of reconstruction kernels, called "basis 
258 

functions" in this context) 
259 

* Large point clouds, with some radial basis function around each point, 
260 

which will be tuned by parameters of the point (at least one parameter 
261 

giving some notion of radius) 
262 


263 
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264 
BUGS ================= 
BUGS ================= 
265 
====================== 
====================== 