Performs the symmetric rank 1 operation.
BLAS Library (libblas.a)
The SSPR or DSPR subroutine performs the symmetric rank 1 operation:
A := alpha * x * x' + A
where alpha is a real scalar, x is an N element vector and A is an N by N symmetric matrix, supplied in packed form.
Item | Description |
---|---|
UPLO | On entry, UPLO specifies whether the upper or lower
triangular part of the matrix A is supplied in the packed array AP as
follows:
Unchanged on exit. |
N | On entry, N specifies the order of the matrix A; N must be at least 0; unchanged on exit. |
ALPHA | On entry, ALPHA specifies the scalar alpha; unchanged on exit. |
X | A vector of dimension at least (1 + (N-1) * abs(INCX) ); on entry, the incremented array X must contain the N element vector x; unchanged on exit. |
INCX | On entry, INCX specifies the increment for the elements of X; INCX must not be 0; unchanged on exit. |
AP | A vector of dimension at least ( ( N * (N+1) )/2 ); on entry with UPLO = 'U' or 'u', the array AP must contain the upper triangular part of the symmetric matrix packed sequentially, column by column, so that AP(1) contains A(1,1), AP(2) and AP(3) contain A(1,2) and A(2,2) respectively, and so on. On exit, the array AP is overwritten by the upper triangular part of the updated matrix. On entry with UPLO = 'L' or 'l', the array AP must contain the lower triangular part of the symmetric matrix packed sequentially, column by column, so that AP(1) contains A(1,1), AP(2) and AP(3) contain A(2,1) and A(3,1) respectively, and so on. On exit, the array AP is overwritten by the lower triangular part of the updated matrix. |