SetDiag

SetDiag routine can be used for setting the diagonal entries of a square dense matrix. The generic call is given below.

CALL SetDiag( mat, d, diagNo )

where,

• mat(:,:) is a square matrix of Real(DFP)
• d(:) is a vector of Real32 | Real64 | Int8 | Int16 | Int32 | Int64.
• If size of d is 1, then it means the diagonal values are constant, otherwise the size of d should be same as the corresponding diagonal of matrix mat. For example, if d is first sub diagonal, then its size should be n-1 (where, n is size of mat).
• diagNo is an integer, which stands for the diagonal number.

܀ See example

In this example we show the usage of SetDiag function. We will extract diagonals from a square matrix.

header

program main
  use easifemBase
  real( DFP ), allocatable :: mat(:, :)
  real( DFP ), allocatable :: d(:)

form random diagonal

  mat = zeros(5,5,1.0_DFP)
  call reallocate(d, size(mat,1))
  call random_number(d)
  d = d * 10
  call display( MdEncode(d), "d = "// CHAR_LF )

set main diagonal

  call SetDiag(mat, d, 0)
  call Display( MdEncode(mat), "mat = " // CHAR_LF)

d =

6.6689	5.5432	6.7909	2.3661	2.1642

mat =

6.6689	0	0	0	0
0	5.5432	0	0	0
0	0	6.7909	0	0
0	0	0	2.3661	0
0	0	0	0	2.1642

See line 5.

set first super-diagonal

  call reallocate(d, size(mat,1)-1)
  call random_number(d)
  d = d * 10
  call display( MdEncode(d), "d = "// CHAR_LF )
  call SetDiag(mat, d, 1)
  call Display( MdEncode(mat), "mat = " // CHAR_LF)

d =

4.594	8.1182	4.0813	0.83561

mat =

6.6689	4.594	0	0	0
0	5.5432	8.1182	0	0
0	0	6.7909	4.0813	0
0	0	0	2.3661	0.83561
0	0	0	0	2.1642

See line 5.

set second super-diagonal

  call reallocate(d, size(mat,1)-2)
  call random_number(d)
  d = d * 10
  call display( MdEncode(d), "d = "// CHAR_LF )
  call SetDiag(mat, d, 2)
  call Display( MdEncode(mat), "mat = " // CHAR_LF)

d =

7.2706	1.6909	6.0739

mat =

6.6689	4.594	7.2706	0	0
0	5.5432	8.1182	1.6909	0
0	0	6.7909	4.0813	6.0739
0	0	0	2.3661	0.83561
0	0	0	0	2.1642

See line 5.

set second sub-diagonal

  call reallocate(d, size(mat,1)-2)
  call random_number(d)
  d = d * 10
  call display( MdEncode(d), "d = "// CHAR_LF )
  call SetDiag(mat, d, -2)
  call Display( MdEncode(mat), "mat = " // CHAR_LF)

d =

8.4214	2.8808	6.9836

mat =

6.6689	4.594	7.2706	0	0
0	5.5432	8.1182	1.6909	0
8.4214	0	6.7909	4.0813	6.0739
0	2.8808	0	2.3661	0.83561
0	0	6.9836	0	2.1642

cleanup

end program

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