Feature #1733

Handle >3 dimensional maps in GSkyMap

Added by Knödlseder Jürgen about 8 years ago. Updated almost 8 years ago.

Status:ClosedStart date:03/05/2016
Priority:NormalDue date:
Assigned To:Knödlseder Jürgen% Done:

100%

Category:-
Target version:1.1.0
Duration:

Description

The GTuple class should implement an integer tuple that can be used to pass an arbitrary number of indices as argument to a method. Use cases for this class are the map argument of the GSkyMap class to allow the creation of n-dimensional map cubes, and the FITS image pixel access operators.

Here a draft of the class:

class GTuple : public GBase {
public:
    // Constructors
    GTuple(void);
    GTuple(const int& i1);
    GTuple(const int& i1, const int& i2);
    GTuple(const int& i1, const int& i2, const int& i3);
    GTuple(const std::vector<int>& index);

    // Operators
    int&       operator[](const int& i);
    const int& operator[](const int& i) const;

    // Methods
    int size(void) const

protected:
    // Data members
    int              m_size;
    int              m_index1;
    int              m_index2;
    int              m_index3;
    std::vector<int> m_index;

Recurrence

No recurrence.

History

#1 Updated by Knödlseder Jürgen almost 8 years ago

I’m not fully sure that a GTuple class is indeed needed. An alternative approach would be to use a variadic function (see http://en.cppreference.com/w/cpp/utility/variadic) to define an arbitrary number of additional dimensions in GSkyMap. The advantage of this approach would be that the current GSkyMap interface could be basically kept, and that GSkyMap would have additional methods for higher map dimensions.

Here some C++ use cases that use an extension of the current format:

GSkyPixel pix;
GSkyDir   dir;
GSkyMap   map("CAR", "CEL", 0.0, 0.0, 0.1, 0.1, 100, 100, 10, 10);
double    value1 = map(pix,0,1);
double    value2 = map(dir,0,1);
and Python use cases
pix    = gammalib.GSkyPixel()
dir    = gammalib.GSkyDir()
map    = gammalib.GSkyMap("CAR", "CEL", 0.0, 0.0, 0.1, 0.1, 100, 100, 10, 10)
value1 = map(pix,0,1)
value2 = map(dir,0,1)

#2 Updated by Knödlseder Jürgen almost 8 years ago

  • Subject changed from Create GTuple class to Handle >3 dimensional than maps in GSkyMap

#3 Updated by Knödlseder Jürgen almost 8 years ago

  • Subject changed from Handle >3 dimensional than maps in GSkyMap to Handle >3 dimensional maps in GSkyMap

#4 Updated by Knödlseder Jürgen almost 8 years ago

It’s maybe sufficient (at least for now) to add a shape() method, along the logic that numpy uses, to define the shape of the maps. For example

GSkyMap map("CAR", "CEL", 0.0, 0.0, 0.1, 0.1, 100, 100, 10);
map.shape(5,2);

would organise the 10 maps in the objects into a two-dimensional array with axes lengths of 5 times 2 (the shape() method would throw an exception in case that the total number of maps in the GSkyMap object is not equal to the product of the shape arguments.

When GSkyMap loads a map it will automatically determine the shape from the FITS file dimension, and compute the total number of maps as the product of the shape parameters.

A method ndim() should be added that returns the dimension of the shape part (in analogy to numpy again).

#5 Updated by Knödlseder Jürgen almost 8 years ago

  • Status changed from New to Closed
  • Assigned To set to Knödlseder Jürgen
  • Target version set to 1.1.0
  • % Done changed from 0 to 100

The change has been implemented, unit tests have been added, is now in devel.

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