Diff of /trunk/TODO

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	revision 1161, Mon May 9 16:40:35 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	SHORT TERM ============= (*needed* for streamlines & tractography)	SHORT TERM ============= (*needed* for streamlines & tractography)
6	========================	========================
7
8	[GLK:1] Add sequence types (needed for evals & evecs)	[GLK:3] 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	[GLK:1] evals & evecs for symmetric tensor[3,3] (requires sequences)
14		[GLK:4] evals & evecs for symmetric tensor[2,2] and
15		tensor[3,3] (requires sequences)
16
17	ability to emit/track/record variables into dynamically re-sized	ability to emit/track/record variables into dynamically re-sized
18	runtime buffer	runtime buffer
#	Line 18	Line 20
20	tensor fields: convolution on general tensor images	tensor fields: convolution on general tensor images
21
22	========================	========================
23	SHORT-ISH TERM ========= (to make using Diderot less annoying/slow)	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	proper handling of stabilize method	[GLK:1] Add a clamp function, which takes three arguments; either
29		three scalars:
30		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
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		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:
63	F = bspln3 ⊛ (img  clamp)	F = bspln3 ⊛ (img ◦ clamp)
64	F = bspln3 ⊛ (img ◦ repeat)	F = bspln3 ⊛ (img ◦ repeat)
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
	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).
68	Level of differentiability in field type should be statement about how	Level of differentiability in field type should be statement about how
69	much differentiation the program *needs*, rather than what the kernel	much differentiation the program *needs*, rather than what the kernel
70	*provides*.  The needed differentiability can be less than or equal to	*provides*.  The needed differentiability can be less than or equal to
71	the provided differentiability.	the provided differentiability.
72
73		Use ∇⊗ etc. syntax
74		syntax [DONE]
75		typechecking
76		IL and codegen
77
78	Add type aliases for color types	Add type aliases for color types
79	rgb = real{3}	rgb = real{3}
80	rgba = real{4}	rgba = real{4}
#	Line 94	Line 105
105
106	support for Python interop and GUI	support for Python interop and GUI
107
108		Allow integer exponentiation ("^2") to apply to square matrices,
109		to represent repeated matrix multiplication
110
111	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,
112	provided that X*Y, X/Y, X+Y, X-Y are already supported.	provided that X*Y, X/Y, X+Y, X-Y are already supported.
113	Nearly every Diderot program would be simplified by this.	Nearly every Diderot program would be simplified by this.
#	Line 142	Line 156
156	(but we should only duplicate over the live-range of the result of the	(but we should only duplicate over the live-range of the result of the
157	conditional.	conditional.
158
159	[GLK:5] Want: non-trivial field expressions & functions:	[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(...);	image(2)[2] Vimg = load(...);
165	field#0(2)[] Vlen = |Vimg ⊛ bspln3|;	field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
166	to get a scalar field of vector length, or	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;	field#2(2)[] F = Fimg ⊛ bspln3;
171	field#0(2)[] Gmag = |∇F|;	field#0(2)[] Gmag = |∇F|;
172	to get a scalar field of gradient magnitude, or	scalar field of squared gradient magnitude (simpler to differentiate):
173	field#2(2)[] F = Fimg ⊛ bspln3;	field#2(2)[] F = Fimg ⊛ bspln3;
174	field#0(2)[] Gmsq = ∇F•∇F;	field#0(2)[] Gmsq = ∇F•∇F;
175	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
176	to differentiate.  However, there is value in having these, even if	not supported (hence the indication of "field#0" for these above)
177	the differentiation of them is not supported (hence the indication
178	of "field#0" for these above)	co- vs contra- index distinction
	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.
179
180	Permit fields composition, especially for warping images by a	Permit field composition:
	smooth field of deformation vectors
181	field#2(3)[3] warp = bspln3 ⊛ warpData;	field#2(3)[3] warp = bspln3 ⊛ warpData;
182	field#2(3)[] F = bspln3 ⊛ img;	field#2(3)[] F = bspln3 ⊛ img;
183	field#2(3)[] Fwarp = F ◦ warp;	field#2(3)[] Fwarp = F ◦ warp;
184	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.
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	Allow the convolution to be specified either as a single 1D kernel
189	(as we have it now):	(as we have it now):
#	Line 177	Line 192
192	field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;	field#0(3)[] F = (bspln3 ⊗ bspln3 ⊗ tent) ⊛ img;
193	This is especially important for things like time-varying data, or	This is especially important for things like time-varying data, or
194	other multi-dimensional fields where one axis of the domain is very	other multi-dimensional fields where one axis of the domain is very
195	different from the rest.  What is very unclear is how, in such cases,	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	we should notate the gradient, when we only want to differentiate with
198	respect to some of the axes.	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	co- vs contra- index distinction	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	some indication of tensor symmetry	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

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