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[diderot] Diff of /branches/tash/TODO
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Diff of /branches/tash/TODO

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trunk/TODO revision 1133, Thu May 5 18:57:15 2011 UTC branches/vis12/TODO revision 1686, Mon Jan 23 18:49:17 2012 UTC
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1  NOTE: GLK's approximate ranking of 5 most important tagged with  This to do for the Vis 2012 submission
 [GLK:1], [GLK:2], ...  
3  ==============================  3rd order tensors: 2x2x2 and 3x3x3
 other SHORT TERM =============  (including needed for LIC)  
5  Add a clamp function, which takes three arguments; either three scalars:  dynamic-length sequences
   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  Level of differentiability in field type should be statement about how  curl 2D and 3D
 much differentiation the program *needs*, rather than what the kernel  
 *provides*.  The needed differentiability can be less than or equal to  
 the provided differentiability.  
9  [GLK:1] Add sequence types (needed for evals & evecs)  support iteration over image indices
         types: ty '{' INT '}'  
         value construction: '{' e1 ',' … ',' en '}'  
         indexing: e '{' e '}'  
 IL support for higher-order tensor values (matrices, etc).  
     tensor construction [DONE]  
     tensor indexing [DONE]  
     tensor slicing  
     verify that hessians work correctly [DONE]  
 Use ∇⊗ etc. syntax  
     syntax [DONE]  
     IL and codegen  
 documents need for better compiler error messages when output variables  
 are not initialized; the current messages are very cryptic  
 determinant ("det") for tensor[3,3]  
 expand trace in mid to low translation  
 value-numbering optimization  
 Add type aliases for color types  
     rgb = real{3}  
     rgba = real{4}  
 MEDIUM TERM ================== (including needed for streamlines & tractography)  
 [GLK:1] evals & evecs for symmetric tensor[3,3] (requires sequences)  
 [GLK:2] Save Diderot output to nrrd, instead of "mip.txt"  
   For grid of strands, save to similarly-shaped array  
   For list of strands, save to long 1-D (or 2-D for non-scalar output) list  
   For ragged things (like tractography output), will need to save both  
     complete list of values, as well as list of start indices and lengths  
     to index into complete list  
 [GLK:3] Use of Teem's "hest" command-line parser for getting  
 any input variables that are not defined in the source file  
 [GLK:4] ability to declare a field so that probe positions are  
 *always* "inside"; with various ways of mapping the known image values  
 to non-existant index locations.  One possible syntax emphasizes that  
 there is a index mapping function that logically precedes convolution:  
   F = bspln3 ⊛ (img ◦ clamp)  
   F = bspln3 ⊛ (img ◦ repeat)  
   F = bspln3 ⊛ (img ◦ mirror)  
 where "◦" or "∘" is used to indicate function composition  
 extend norm (|exp|) to all tensor types [DONE for vectors and matrices]  
 ability to emit/track/record variables into dynamically re-sized  
 runtime buffer  
 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.  
 Want: non-trivial field expressions & functions:  
   image(2)[2] Vimg = load(...);  
   field#0(2)[] Vlen = |Vimg ⊛ bspln3|;  
 to get a scalar field of vector length, or  
   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.  
 tensor fields: convolution on general tensor images  
 other MEDIUM TERM ============ (needed for particles)  
 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  
 run-time birth of strands  
 "initially" supports lists  
 "initially" supports lists of positions output from  
 different initalization Diderot program  
 spatial data structure that permits strands' queries of neighbors  
 proper handling of stabilize method  
 test/vr-kcomp2.diderot: Add support for code like  
         (F1 if x else F2)@pos  
 This will require duplication of the continuation of the conditional  
 (but we should only duplicate over the live-range of the result of the  
 add ":" for tensor dot product (contracts out two indices  
 instead of one like •), valid for all pairs of tensors with  
 at least two indices  
 other MEDIUM TERM ============  
 want: warnings when "D" (reserved for differentiation) is declared as  
 a variable name (get confusing error messages now)  
 support for Python interop and GUI  
 Python/ctypes interface to run-time  
 LONG TERM ====================  
 Better handling of variables that determines the scope of a variable  
 based on its actual use, instead of where the user defined it.  So,  
 for example, we should lift strand-invariant variables to global  
 scope.  Also prune out useless variables, which should include field  
 variables after the translation to mid-il.  
 co- vs contra- index distinction  
 some indication of tensor symmetry  
 (have to identify the group of index permutations that are symmetries)  
 dot works on all tensors  
 outer works on all tensors  
 Einstein summation notation  
 "tensor comprehension" (like list comprehension)  
 BUGS =================  
 // 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");  
 // HEY (bug) bspln5 leads to problems ...  
 //  uncaught exception Size [size]  
 //    raised at c-target/c-target.sml:47.15-47.19  
 //field#4(3)[] F = img ⊛ bspln5;  

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