Diff of /branches/vis12-cl/TODO

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	revision 1133, Thu May 5 18:57:15 2011 UTC	revision 1162, Mon May 9 18:56:15 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]
	Use ∇⊗ etc. syntax
	syntax [DONE]
	typechecking
	IL and codegen
16
17	test/uninit.diderot:	ability to emit/track/record variables into dynamically re-sized
18	documents need for better compiler error messages when output variables	runtime buffer
	are not initialized; the current messages are very cryptic
19
20	determinant ("det") for tensor[3,3]	tensor fields: convolution on general tensor images
21
22	expand trace in mid to low translation	========================
23		SHORT-ISH TERM ========= (to make using Diderot less annoying to
24		========================  program in, and slow to execute)
25
26	value-numbering optimization	value-numbering optimization
27
28	Add type aliases for color types	[GLK:1] Add a clamp function, which takes three arguments; either
29	rgb = real{3}	three scalars:
30	rgba = real{4}	clamp(lo, hi, x)  = max(lo, min(hi, x))
31		or three vectors of the same size:
32		clamp(lo, hi, [x,y])  = [max(lo[0], min(hi[0], x)),
33		max(lo[1], min(hi[1], y))]
34		This would be useful in many current Diderot programs.
35		One question: clamp(x, lo, hi) is the argument order used in OpenCL
36		and other places, but clamp(lo, hi, x) is much more consistent with
37		lerp(lo, hi, x), hence GLK's preference
38
39	==============================	[GLK:2] Proper handling of stabilize method
40	MEDIUM TERM ================== (including needed for streamlines & tractography)
41	==============================	allow "*" to represent "modulate": per-component multiplication of
42		vectors, and vectors only (not tensors of order 2 or higher).  Once
43		sequences are implemented this should be removed: the operation is not
44		invariant WRT basis so it is not a legit vector computation.
45
46	[GLK:1] evals & evecs for symmetric tensor[3,3] (requires sequences)	implicit type promotion of integers to reals where reals are
47		required (e.g. not exponentiation "^")
48
49	[GLK:2] Save Diderot output to nrrd, instead of "mip.txt"	[GLK:5] Save Diderot output to nrrd, instead of "mip.txt"
50	For grid of strands, save to similarly-shaped array	For grid of strands, save to similarly-shaped array
51	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
52	For ragged things (like tractography output), will need to save both	For ragged things (like tractography output), will need to save both
53	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
54	to index into complete list	to index into complete list
55
56	[GLK:3] Use of Teem's "hest" command-line parser for getting	[GLK:6] Use of Teem's "hest" command-line parser for getting
57	any input variables that are not defined in the source file	any input variables that are not defined in the source file
58
59	[GLK:4] ability to declare a field so that probe positions are	[GLK:7] ability to declare a field so that probe positions are
60	*always* "inside"; with various ways of mapping the known image values	*always* "inside"; with various ways of mapping the known image values
61	to non-existant index locations.  One possible syntax emphasizes that	to non-existant index locations.  One possible syntax emphasizes that
62	there is a index mapping function that logically precedes convolution:	there is a index mapping function that logically precedes convolution:
#	Line 76	Line 65
65	F = bspln3 ⊛ (img ◦ mirror)	F = bspln3 ⊛ (img ◦ mirror)
66	where "◦" or "∘" is used to indicate function composition	where "◦" or "∘" is used to indicate function composition
67
68	extend norm (|exp|) to all tensor types [DONE for vectors and matrices]	Level of differentiability in field type should be statement about how
69		much differentiation the program *needs*, rather than what the kernel
70	ability to emit/track/record variables into dynamically re-sized	*provides*.  The needed differentiability can be less than or equal to
71	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.
72
73	Want: non-trivial field expressions & functions:	Use ∇⊗ etc. syntax
74	image(2)[2] Vimg = load(...);	syntax [DONE]
75	field#0(2)[] Vlen = |Vimg ⊛ bspln3|;	typechecking
76	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.
77
78	tensor fields: convolution on general tensor images	Add type aliases for color types
79		rgb = real{3}
80		rgba = real{4}
81
82	==============================	==============================
83	other MEDIUM TERM ============ (needed for particles)	MEDIUM TERM ================== (*needed* for particles)
84	==============================	==============================
85
	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
86	run-time birth of strands	run-time birth of strands
87
88	"initially" supports lists	"initially" supports lists
#	Line 124	Line 90
90	"initially" supports lists of positions output from	"initially" supports lists of positions output from
91	different initalization Diderot program	different initalization Diderot program
92
93	spatial data structure that permits strands' queries of neighbors	Communication between strands: they have to be able to learn each
94		other's state (at the previous iteration).  Early version of this can
95		have the network of neighbors be completely static (for running one
96		strand/pixel image computations).  Later version with strands moving
97		through the domain will require some spatial data structure to
98		optimize discovery of neighbors.
99
100		============================
101		MEDIUM-ISH TERM ============ (to make Diderot more useful/effective)
102		============================
103
104	proper handling of stabilize method	Python/ctypes interface to run-time
105
106	test/vr-kcomp2.diderot: Add support for code like	support for Python interop and GUI
107
108	(F1 if x else F2)@pos	Allow integer exponentiation ("^2") to apply to square matrices,
109		to represent repeated matrix multiplication
110
111	This will require duplication of the continuation of the conditional	Alow X *= Y, X /= Y, X += Y, X -= Y to mean what they do in C,
112	(but we should only duplicate over the live-range of the result of the	provided that X*Y, X/Y, X+Y, X-Y are already supported.
113	conditional.	Nearly every Diderot program would be simplified by this.
114
115		Put small 1-D and 2-D fields, when reconstructed specifically by tent
116		and when differentiation is not needed, into faster texture buffers.
117		test/illust-vr.diderot is good example of program that uses multiple
118		such 1-D fields basically as lookup-table-based function evaluation
119
120		expand trace in mid to low translation
121
122		extend norm (|exp|) to all tensor types [DONE for vectors and matrices]
123
124		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		verify that hessians work correctly [DONE]
146
147	Better handling of variables that determines the scope of a variable	Better handling of variables that determines the scope of a variable
148	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 161	Line 150
150	scope.  Also prune out useless variables, which should include field	scope.  Also prune out useless variables, which should include field
151	variables after the translation to mid-il.	variables after the translation to mid-il.
152
153		test/vr-kcomp2.diderot: Add support for code like
154		(F1 if x else F2)@pos
155		This will require duplication of the continuation of the conditional
156		(but we should only duplicate over the live-range of the result of the
157		conditional.
158
159		[GLK:8] Want: non-trivial field expressions & functions.
160		scalar fields from scalar fields F and G:
161		field#0(2)[] X = (sin(F) + 1.0)/2;
162		field#0(2)[] X = F*G;
163		scalar field of vector field magnitude:
164		image(2)[2] Vimg = load(...);
165		field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
166		field of normalized vectors (for LIC and vector field feature extraction)
167		field#2(2)[2] F = ...
168		field#0(2)[2] V = normalize(F);
169		scalar field of gradient magnitude (for edge detection))
170		field#2(2)[] F = Fimg ⊛ bspln3;
171		field#0(2)[] Gmag = |∇F|;
172		scalar field of squared gradient magnitude (simpler to differentiate):
173		field#2(2)[] F = Fimg ⊛ bspln3;
174		field#0(2)[] Gmsq = ∇F•∇F;
175		There is value in having these, even if the differentiation of them is
176		not supported (hence the indication of "field#0" for these above)
177
178	co- vs contra- index distinction	co- vs contra- index distinction
179
180	some indication of tensor symmetry	Permit field composition:
181		field#2(3)[3] warp = bspln3 ⊛ warpData;
182		field#2(3)[] F = bspln3 ⊛ img;
183		field#2(3)[] Fwarp = F ◦ warp;
184		So Fwarp(x) = F(warp(X)).  Chain rule can be used for differentation.
185		This will be instrumental for expressing non-rigid registration
186		methods (but those will require co-vs-contra index distinction)
187
188		Allow the convolution to be specified either as a single 1D kernel
189		(as we have it now):
190		field#2(3)[] F = bspln3 ⊛ img;
191		or, as a tensor product of kernels, one for each axis, e.g.
192		field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
193		This is especially important for things like time-varying data, or
194		other multi-dimensional fields where one axis of the domain is very
195		different from the rest, and hence must be treated separately when
196		it comes to convolution.  What is very unclear is how, in such cases,
197		we should notate the gradient, when we only want to differentiate with
198		respect to some subset of the axes.  One ambitious idea would be:
199		field#0(3)[] Ft = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img; // 2D time-varying field
200		field#0(2)[] F = lambda([x,y], Ft([x,y,42.0]))    // restriction to time=42.0
201		vec2 grad = ∇F([x,y]);                            // 2D gradient
202
203		representation of tensor symmetry
204	(have to identify the group of index permutations that are symmetries)	(have to identify the group of index permutations that are symmetries)
205
206	dot works on all tensors	dot works on all tensors
#	Line 178	Line 215
215	BUGS =================	BUGS =================
216	======================	======================
217
	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");
218	test/zslice2.diderot:	test/zslice2.diderot:
219	// HEY (bug) bspln5 leads to problems ...	// HEY (bug) bspln5 leads to problems ...
220	//  uncaught exception Size [size]	//  uncaught exception Size [size]

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