From: Ronald Garcia (garcia_at_[hidden])
Date: 2008-06-16 10:17:24
Hi Joey,
I can't quite follow what you are trying to do below. Could you boil
it down to a small self-contained program that I can compile and run?
Thanks,
ron
On Jun 14, 2008, at 10:32 AM, Joey Mukherjee wrote:
>
> I am trying to use boost::multi_array and want to create a view
> where I am
> lowering the number of dimensions, but I wish the dimension to be
> reduced
> to be decided at runtime.
>
> I have a vector of integers and this vector size is the same as the
> number
> of dimensions. If the vector [1] value is -1, then the first
> dimension
> will have all values (i.e. range ()), otherwise it will be a number
> indicating what slice to use.
>
> You can see in case 2 what I have tried and maybe what I am trying
> to do.
> Case 3 and 4 I am hard coding the dimensions where I want all
> values, which
> does work, but I'd like to get rid of the hard-codedness and make
> this more
> generic.
>
> Furthermore, I have a one dimensional array of values which I am
> "converting" to a boost::multi_array so I can slice into it with
> the views.
> I won't know the dimensions until I read the data. Is there a
> better more
> generic way of doing this? Something like a pointer to a N-
> dimensional
> structure where I can just use the view?
>
> Thanks in advance for any ideas!
>
> Joey
>
> Here is my code:
>
> {
> double ret_val;
> typedef boost::multi_array_types::index_range range;
>
> const VariableInfo &vinfo = GetVariable (si._sensor);
> SubSensorType local_subsensors (si._subsensors);
> assert (local_subsensors.size () == vinfo._sizes.size ());
> switch (vinfo._sizes.size ()) {
> case 0 : ret_val = vals [0];
> break;
> case 1 : { // one-d array
> ret_val = (vals [whichPosition]);
> }
> break;
>
> // Now we get into slices, find the subsensor element that has -1, and
> // create a slice along that dimension
>
> case 2 : { // two-dimensional array
> typedef boost::const_multi_array_ref <double, 2> array_type;
> array_type::index_gen indices;
>
> array_type multi_array (&(vals [0]), vinfo._sizes);
> /*
>
> This doesn't work!
>
> array_type::const_array_view <1>::type OneDView;
> if (local_subsensors [0] == -1)
> OneDView = multi_array [indices [range ()]
> [local_subsensors [1]]];
> else
> if (local_subsensors [1] == -1)
> OneDView = multi_array [indices [local_subsensors [0]
> [range ()]]];
>
> ret_val = (OneDView [whichPosition]);
> */
> }
> break;
> case 3 : { // three-dimensional array
>
> typedef boost::const_multi_array_ref <double, 3>
> array_type;
> array_type::index_gen indices;
>
> array_type multi_array (&(vals [0]), vinfo._sizes);
> array_type::const_array_view <1>::type OneDView =
> multi_array [indices [local_subsensors [0]]
> [local_subsensors [1]]
> [range ()]];
> ret_val = (OneDView [whichPosition]);
> }
> break;
> case 4 : { // four-dimensional array
> typedef boost::const_multi_array_ref <double, 4>
> array_type;
> array_type::index_gen indices;
>
> array_type multi_array (&(vals [0]), vinfo._sizes);
> array_type::const_array_view <1>::type OneDView =
> multi_array [indices [local_subsensors [0]]
> [local_subsensors [1]]
> [local_subsensors [2]]
> [range ()]];
>
> ret_val = (OneDView [whichPosition]);
> }
> break;
> default : assert (vinfo._sizes.size () < 4);
>
> }
> return (ret_val);
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