Rank-1 update

SSPR/DSPR/CHPR/ZHPR

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).

Usage

VECLIB:

 

 

CHARACTER*1

uplo

 

INTEGER*4

n, incx

 

REAL*4

alpha, ap(lenap), x(lenx)

 

CALL SSPR(uplo, n, alpha, x, incx, ap)

 

CHARACTER*1

uplo

 

INTEGER*4

n, incx

 

REAL*8

alpha, ap(lenap), x(lenx)

 

CALL DSPR(uplo, n, alpha, x, incx, ap)

 

CHARACTER*1

uplo

 

INTEGER*4

n, incx

 

REAL*4

alpha

 

COMPLEX*8

ap(lenap), x(lenx)

 

CALL CHPR(uplo, n, alpha, x, incx, ap)

 

CHARACTER*1

uplo

 

INTEGER*4

n, incx

 

REAL*8

alpha

 

COMPLEX*16

ap(lenap), x(lenx)

CALL ZHPR(uplo, n, alpha, x, incx, ap)

Chapter 3 Basic Matrix Operations 255