Annotation of /trunk/TODO

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Revision 1167 - (view) (download)

1 :	glk	1162	NOTE: GLK's approximate ranking of 8 most important tagged with
2 :	jhr	1115	[GLK:1], [GLK:2], ...
3 :
4 :	glk	1156	========================
5 :			SHORT TERM ============= (*needed* for streamlines & tractography)
6 :			========================
7 :	jhr	1115
8 :	glk	1162	[GLK:3] Add sequence types (needed for evals & evecs)
9 :	jhr	1115	syntax
10 :			types: ty '{' INT '}'
11 :			value construction: '{' e1 ',' … ',' en '}'
12 :			indexing: e '{' e '}'
13 :
14 :	glk	1162	[GLK:4] evals & evecs for symmetric tensor[2,2] and
15 :			tensor[3,3] (requires sequences)
16 :
17 :	glk	1156	ability to emit/track/record variables into dynamically re-sized
18 :			runtime buffer
19 :	jhr	1115
20 :	glk	1156	tensor fields: convolution on general tensor images
21 :	jhr	1115
22 :	glk	1156	========================
23 :	glk	1162	SHORT-ISH TERM ========= (to make using Diderot less annoying to
24 :			======================== program in, and slow to execute)
25 :	jhr	1115
26 :	jhr	1165	value-numbering optimization [DONE, but needs more testing]
27 :	jhr	1115
28 :	glk	1167	Allow ".ddro" file extensions in addition to ".diderot"
29 :
30 :			Be able to output values of type tensor[2,2] and tensor[3,3]
31 :			(currently only scalars & vectors)
32 :
33 :	glk	1162	[GLK:1] Add a clamp function, which takes three arguments; either
34 :			three scalars:
35 :			clamp(lo, hi, x) = max(lo, min(hi, x))
36 :			or three vectors of the same size:
37 :			clamp(lo, hi, [x,y]) = [max(lo[0], min(hi[0], x)),
38 :			max(lo[1], min(hi[1], y))]
39 :			This would be useful in many current Diderot programs.
40 :			One question: clamp(x, lo, hi) is the argument order used in OpenCL
41 :			and other places, but clamp(lo, hi, x) is much more consistent with
42 :			lerp(lo, hi, x), hence GLK's preference
43 :	jhr	1115
44 :	glk	1162	[GLK:2] Proper handling of stabilize method
45 :
46 :			allow "*" to represent "modulate": per-component multiplication of
47 :			vectors, and vectors only (not tensors of order 2 or higher). Once
48 :			sequences are implemented this should be removed: the operation is not
49 :			invariant WRT basis so it is not a legit vector computation.
50 :
51 :			implicit type promotion of integers to reals where reals are
52 :			required (e.g. not exponentiation "^")
53 :
54 :			[GLK:5] Save Diderot output to nrrd, instead of "mip.txt"
55 :	jhr	1115	For grid of strands, save to similarly-shaped array
56 :			For list of strands, save to long 1-D (or 2-D for non-scalar output) list
57 :			For ragged things (like tractography output), will need to save both
58 :			complete list of values, as well as list of start indices and lengths
59 :			to index into complete list
60 :
61 :	glk	1162	[GLK:6] Use of Teem's "hest" command-line parser for getting
62 :	jhr	1115	any input variables that are not defined in the source file
63 :
64 :	glk	1162	[GLK:7] ability to declare a field so that probe positions are
65 :	glk	1120	*always* "inside"; with various ways of mapping the known image values
66 :			to non-existant index locations. One possible syntax emphasizes that
67 :			there is a index mapping function that logically precedes convolution:
68 :	glk	1162	F = bspln3 ⊛ (img ◦ clamp)
69 :	glk	1120	F = bspln3 ⊛ (img ◦ repeat)
70 :			F = bspln3 ⊛ (img ◦ mirror)
71 :			where "◦" or "∘" is used to indicate function composition
72 :	jhr	1115
73 :	glk	1162	Level of differentiability in field type should be statement about how
74 :			much differentiation the program *needs*, rather than what the kernel
75 :			*provides*. The needed differentiability can be less than or equal to
76 :			the provided differentiability.
77 :
78 :	glk	1156	Use ∇⊗ etc. syntax
79 :			syntax [DONE]
80 :			typechecking
81 :			IL and codegen
82 :	jhr	1115
83 :	glk	1156	Add type aliases for color types
84 :			rgb = real{3}
85 :			rgba = real{4}
86 :	jhr	1115
87 :			==============================
88 :	glk	1156	MEDIUM TERM ================== (*needed* for particles)
89 :	jhr	1115	==============================
90 :
91 :			run-time birth of strands
92 :
93 :			"initially" supports lists
94 :
95 :			"initially" supports lists of positions output from
96 :			different initalization Diderot program
97 :
98 :	glk	1156	Communication between strands: they have to be able to learn each
99 :			other's state (at the previous iteration). Early version of this can
100 :			have the network of neighbors be completely static (for running one
101 :			strand/pixel image computations). Later version with strands moving
102 :			through the domain will require some spatial data structure to
103 :			optimize discovery of neighbors.
104 :	jhr	1115
105 :	glk	1156	============================
106 :			MEDIUM-ISH TERM ============ (to make Diderot more useful/effective)
107 :			============================
108 :	jhr	1115
109 :	glk	1156	Python/ctypes interface to run-time
110 :	jhr	1115
111 :	glk	1156	support for Python interop and GUI
112 :	jhr	1115
113 :	glk	1162	Allow integer exponentiation ("^2") to apply to square matrices,
114 :			to represent repeated matrix multiplication
115 :
116 :	glk	1156	Alow X *= Y, X /= Y, X += Y, X -= Y to mean what they do in C,
117 :			provided that X*Y, X/Y, X+Y, X-Y are already supported.
118 :			Nearly every Diderot program would be simplified by this.
119 :	jhr	1115
120 :	glk	1156	Put small 1-D and 2-D fields, when reconstructed specifically by tent
121 :			and when differentiation is not needed, into faster texture buffers.
122 :			test/illust-vr.diderot is good example of program that uses multiple
123 :			such 1-D fields basically as lookup-table-based function evaluation
124 :
125 :			expand trace in mid to low translation
126 :
127 :			extend norm (|exp|) to all tensor types [DONE for vectors and matrices]
128 :
129 :			determinant ("det") for tensor[3,3]
130 :
131 :	jhr	1115	add ":" for tensor dot product (contracts out two indices
132 :			instead of one like •), valid for all pairs of tensors with
133 :			at least two indices
134 :
135 :	glk	1156	test/uninit.diderot:
136 :			documents need for better compiler error messages when output variables
137 :			are not initialized; the current messages are very cryptic
138 :	jhr	1115
139 :			want: warnings when "D" (reserved for differentiation) is declared as
140 :			a variable name (get confusing error messages now)
141 :
142 :	glk	1156	==============================
143 :			LONG TERM ==================== (make Diderot more interesting/attractive from
144 :			============================== a research standpoint)
145 :	jhr	1115
146 :	glk	1156	IL support for higher-order tensor values (matrices, etc).
147 :			tensor construction [DONE]
148 :			tensor indexing [DONE]
149 :			tensor slicing
150 :			verify that hessians work correctly [DONE]
151 :	jhr	1115
152 :	glk	1156	Better handling of variables that determines the scope of a variable
153 :			based on its actual use, instead of where the user defined it. So,
154 :			for example, we should lift strand-invariant variables to global
155 :			scope. Also prune out useless variables, which should include field
156 :			variables after the translation to mid-il.
157 :
158 :			test/vr-kcomp2.diderot: Add support for code like
159 :			(F1 if x else F2)@pos
160 :			This will require duplication of the continuation of the conditional
161 :			(but we should only duplicate over the live-range of the result of the
162 :			conditional.
163 :
164 :	glk	1162	[GLK:8] Want: non-trivial field expressions & functions.
165 :			scalar fields from scalar fields F and G:
166 :			field#0(2)[] X = (sin(F) + 1.0)/2;
167 :			field#0(2)[] X = F*G;
168 :			scalar field of vector field magnitude:
169 :	glk	1156	image(2)[2] Vimg = load(...);
170 :			field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
171 :	glk	1162	field of normalized vectors (for LIC and vector field feature extraction)
172 :			field#2(2)[2] F = ...
173 :			field#0(2)[2] V = normalize(F);
174 :			scalar field of gradient magnitude (for edge detection))
175 :	glk	1156	field#2(2)[] F = Fimg ⊛ bspln3;
176 :			field#0(2)[] Gmag = |∇F|;
177 :	glk	1162	scalar field of squared gradient magnitude (simpler to differentiate):
178 :	glk	1156	field#2(2)[] F = Fimg ⊛ bspln3;
179 :			field#0(2)[] Gmsq = ∇F•∇F;
180 :	glk	1162	There is value in having these, even if the differentiation of them is
181 :			not supported (hence the indication of "field#0" for these above)
182 :	glk	1156
183 :	glk	1162	co- vs contra- index distinction
184 :	glk	1156
185 :	glk	1162	Permit field composition:
186 :	glk	1156	field#2(3)[3] warp = bspln3 ⊛ warpData;
187 :			field#2(3)[] F = bspln3 ⊛ img;
188 :			field#2(3)[] Fwarp = F ◦ warp;
189 :	glk	1162	So Fwarp(x) = F(warp(X)). Chain rule can be used for differentation.
190 :			This will be instrumental for expressing non-rigid registration
191 :			methods (but those will require co-vs-contra index distinction)
192 :	glk	1156
193 :	glk	1155	Allow the convolution to be specified either as a single 1D kernel
194 :			(as we have it now):
195 :			field#2(3)[] F = bspln3 ⊛ img;
196 :			or, as a tensor product of kernels, one for each axis, e.g.
197 :			field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
198 :			This is especially important for things like time-varying data, or
199 :			other multi-dimensional fields where one axis of the domain is very
200 :	glk	1162	different from the rest, and hence must be treated separately when
201 :			it comes to convolution. What is very unclear is how, in such cases,
202 :	glk	1155	we should notate the gradient, when we only want to differentiate with
203 :	glk	1162	respect to some subset of the axes. One ambitious idea would be:
204 :			field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D time-varying field
205 :			field#0(2)[] F = lambda([x,y], Ft([x,y,42.0])) // restriction to time=42.0
206 :			vec2 grad = ∇F([x,y]); // 2D gradient
207 :	glk	1155
208 :	glk	1162	representation of tensor symmetry
209 :	jhr	1115	(have to identify the group of index permutations that are symmetries)
210 :
211 :			dot works on all tensors
212 :
213 :			outer works on all tensors
214 :
215 :			Einstein summation notation
216 :
217 :			"tensor comprehension" (like list comprehension)
218 :
219 :			======================
220 :			BUGS =================
221 :			======================
222 :
223 :			test/zslice2.diderot:
224 :			// HEY (bug) bspln5 leads to problems ...
225 :			// uncaught exception Size [size]
226 :			// raised at c-target/c-target.sml:47.15-47.19
227 :			//field#4(3)[] F = img ⊛ bspln5;

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