Annotation of /branches/pure-cfg/TODO

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1 :	glk	1049	NOTE: GLK's approximate ranking of 5 most important tagged with
2 :	glk	962	[GLK:1], [GLK:2], ...
3 :
4 :	glk	1049	==============================
5 :			other SHORT TERM ============= (including needed for LIC)
6 :			==============================
7 :	glk	781
8 :	jhr	1127	Add a clamp function, which takes three arguments; either three scalars:
9 :			clamp(x, minval, maxval) = max(minval, min(maxval, x))
10 :			or three vectors of the same size:
11 :			clamp([x,y], minvec, maxvec) = [max(minvec[0], min(maxvec[0], x)),
12 :			max(minvec[1], min(maxvec[1], y))]
13 :			This would be useful in many current Diderot programs.
14 :			One question: clamp(x, minval, maxval) is the argument order
15 :			used in OpenCL and other places, but clamp(minval, maxval, x)
16 :			would be more consistent with lerp(minout, maxout, x).
17 :
18 :			Level of differentiability in field type should be statement about how
19 :			much differentiation the program *needs*, rather than what the kernel
20 :			*provides*. The needed differentiability can be less than or equal to
21 :			the provided differentiability.
22 :
23 :	glk	1049	[GLK:1] Add sequence types (needed for evals & evecs)
24 :			syntax
25 :			types: ty '{' INT '}'
26 :			value construction: '{' e1 ',' … ',' en '}'
27 :			indexing: e '{' e '}'
28 :
29 :	jhr	788	IL support for higher-order tensor values (matrices, etc).
30 :	jhr	803	tensor construction [DONE]
31 :			tensor indexing [DONE]
32 :			tensor slicing
33 :	jhr	853	verify that hessians work correctly [DONE]
34 :	jhr	788
35 :			Use ∇⊗ etc. syntax
36 :	jhr	763	syntax [DONE]
37 :			typechecking
38 :			IL and codegen
39 :
40 :	glk	927	test/uninit.diderot:
41 :	glk	941	documents need for better compiler error messages when output variables
42 :	glk	927	are not initialized; the current messages are very cryptic
43 :
44 :	glk	785	determinant ("det") for tensor[3,3]
45 :
46 :	jhr	788	expand trace in mid to low translation
47 :
48 :			value-numbering optimization
49 :
50 :			Add type aliases for color types
51 :			rgb = real{3}
52 :			rgba = real{4}
53 :
54 :	glk	781	==============================
55 :	glk	891	MEDIUM TERM ================== (including needed for streamlines & tractography)
56 :	glk	781	==============================
57 :
58 :	glk	1049	[GLK:1] evals & evecs for symmetric tensor[3,3] (requires sequences)
59 :	glk	962
60 :	glk	1049	[GLK:2] Save Diderot output to nrrd, instead of "mip.txt"
61 :	glk	962	For grid of strands, save to similarly-shaped array
62 :			For list of strands, save to long 1-D (or 2-D for non-scalar output) list
63 :			For ragged things (like tractography output), will need to save both
64 :			complete list of values, as well as list of start indices and lengths
65 :			to index into complete list
66 :
67 :	glk	1049	[GLK:3] Use of Teem's "hest" command-line parser for getting
68 :	glk	962	any input variables that are not defined in the source file
69 :
70 :	jhr	1127	[GLK:4] ability to declare a field so that probe positions are
71 :			*always* "inside"; with various ways of mapping the known image values
72 :			to non-existant index locations. One possible syntax emphasizes that
73 :			there is a index mapping function that logically precedes convolution:
74 :			F = bspln3 ⊛ (img ◦ clamp)
75 :			F = bspln3 ⊛ (img ◦ repeat)
76 :			F = bspln3 ⊛ (img ◦ mirror)
77 :			where "◦" or "∘" is used to indicate function composition
78 :	glk	962
79 :	glk	1049	extend norm (|exp|) to all tensor types [DONE for vectors and matrices]
80 :
81 :	glk	962	ability to emit/track/record variables into dynamically re-sized
82 :			runtime buffer
83 :
84 :	glk	945	Want: allow X *= Y, X /= Y, X += Y, X -= Y to mean what they do in C,
85 :			provided that X*Y, X/Y, X+Y, X-Y are already supported.
86 :			Nearly every Diderot program would be simplified by this.
87 :
88 :	glk	962	Want: non-trivial field expressions & functions:
89 :	glk	948	image(2)[2] Vimg = load(...);
90 :	glk	950	field#0(2)[] Vlen = |Vimg ⊛ bspln3|;
91 :	glk	948	to get a scalar field of vector length, or
92 :	glk	950	field#2(2)[] F = Fimg ⊛ bspln3;
93 :			field#0(2)[] Gmag = |∇F|;
94 :	glk	948	to get a scalar field of gradient magnitude, or
95 :	glk	950	field#2(2)[] F = Fimg ⊛ bspln3;
96 :			field#0(2)[] Gmsq = ∇F•∇F;
97 :			to get a scalar field of squared gradient magnitude, which is simpler
98 :	glk	962	to differentiate. However, there is value in having these, even if
99 :			the differentiation of them is not supported (hence the indication
100 :			of "field#0" for these above)
101 :	glk	945
102 :	glk	962	Want: ability to apply "normalize" to a field itself, e.g.
103 :			field#0(2)[2] V = normalize(Vimg ⊛ ctmr);
104 :			so that V(x) = normalize((Vimg ⊛ ctmr)(x)).
105 :			Having this would simplify expression of standard LIC method, and
106 :			would also help express other vector field expressions that arise
107 :			in vector field feature exraction.
108 :	glk	941
109 :	glk	781	tensor fields: convolution on general tensor images
110 :
111 :			==============================
112 :			other MEDIUM TERM ============ (needed for particles)
113 :			==============================
114 :
115 :	glk	1049	[GLK:5] run-time death of strands; test/iso2d.diderot provides
116 :			great initial test for "die" command.
117 :	glk	781
118 :	jhr	1127	Put small 1-D and 2-D fields, when reconstructed specifically by tent
119 :			and when differentiation is not needed, into faster texture buffers.
120 :			test/illust-vr.diderot is good example of program that uses multiple
121 :			such 1-D fields basically as lookup-table-based function evaluation
122 :
123 :	glk	1049	run-time birth of strands
124 :
125 :	glk	781	"initially" supports lists
126 :
127 :			"initially" supports lists of positions output from
128 :			different initalization Diderot program
129 :
130 :			spatial data structure that permits strands' queries of neighbors
131 :
132 :	jhr	784	proper handling of stabilize method
133 :
134 :	glk	891	test/vr-kcomp2.diderot: Add support for code like
135 :	jhr	796
136 :			(F1 if x else F2)@pos
137 :
138 :	glk	962	This will require duplication of the continuation of the conditional
139 :			(but we should only duplicate over the live-range of the result of the
140 :			conditional.
141 :	jhr	796
142 :	glk	1049	add ":" for tensor dot product (contracts out two indices
143 :			instead of one like •), valid for all pairs of tensors with
144 :			at least two indices
145 :
146 :	glk	781	==============================
147 :	jhr	797	other MEDIUM TERM ============
148 :			==============================
149 :
150 :	glk	927	want: warnings when "D" (reserved for differentiation) is declared as
151 :			a variable name (get confusing error messages now)
152 :	jhr	797
153 :	jhr	824	support for Python interop and GUI
154 :
155 :	glk	1049	Python/ctypes interface to run-time
156 :
157 :	jhr	797	==============================
158 :	glk	781	LONG TERM ====================
159 :			==============================
160 :
161 :	glk	927	Better handling of variables that determines the scope of a variable
162 :			based on its actual use, instead of where the user defined it. So,
163 :			for example, we should lift strand-invariant variables to global
164 :			scope. Also prune out useless variables, which should include field
165 :			variables after the translation to mid-il.
166 :	jhr	796
167 :	glk	781	co- vs contra- index distinction
168 :
169 :			some indication of tensor symmetry
170 :			(have to identify the group of index permutations that are symmetries)
171 :
172 :			dot works on all tensors
173 :
174 :			outer works on all tensors
175 :
176 :			Einstein summation notation
177 :
178 :			"tensor comprehension" (like list comprehension)
179 :	jhr	784
180 :			======================
181 :			BUGS =================
182 :			======================
183 :
184 :	glk	962	test/read2vecs.diderot:
185 :			// HEY (BUG?) shouldn't it be a type error to load this 2-D array of
186 :			// 2-vectors into a 2-D *scalar* field? Instead, get:
187 :			// uncaught exception Fail [Fail: Error in compiling lic.diderot]
188 :			// raised at driver/main.sml:31.39-31.76
189 :			image(2)[] Vimg = load("../data/vorttest.nrrd");
190 :
191 :	jhr	784	test/zslice2.diderot:
192 :			// HEY (bug) bspln5 leads to problems ...
193 :			// uncaught exception Size [size]
194 :			// raised at c-target/c-target.sml:47.15-47.19
195 :			//field#4(3)[] F = img ⊛ bspln5;

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