SSPR2/DSPR2/CHPR2/ZHPR2

Rank-2 update

Upper triangular storage

If the upper triangle of A is

11 12 13 14

22 23 24

33 34

44

then A is packed column-by-column into an array ap as follows:

k

1

2

3

4

5

6

7

8

9

10

ap(k)

11

12

22

13

23

33

14

24

34

44

 

 

 

 

 

 

 

 

 

 

 

Upper triangular matrix element aij is stored in array element ap(i+(j⋅(j−1))/2).

Lower triangular storage

If the lower triangle of A is

11

21 22

31 32 33

41 42 43 44

then A is packed column-by-column into an array ap as follows:

k

1

2

3

4

5

6

7

8

9

10

ap(k)

11

21

31

41

22

32

42

33

43

44

 

 

 

 

 

 

 

 

 

 

 

Lower triangular matrix element aij is stored in array element ap(i+((j−1)⋅(2n−j))/2).

260HP MLIB User’s Guide