If N <= 0 or H is an identity matrix, the subroutines return immediately.
Applies the modified Givens transformation.
BLAS Library (libblas.a)
Let H denote the modified Givens transformation defined by the parameter array PARAM. The SROTM or DROTM subroutine computes:
--- --- --- ---
| x | | x |
| | := H * | |
| y | | y |
--- --- --- ---
where H is a 2 x 2 matrix with the components defined by the elements of the array PARAM as follows:
if PARAM(1) == 0.0
H(1,1) = H(2,2) = 1.0
H(2,1) = PARAM(3)
H(1,2) = PARAM(4)
if PARAM(1) == 1.0
H(1,2) = H(2,1) = -1.0
H(1,1) = PARAM(2)
H(2,2) = PARAM(5)
if PARAM(1) == -1.0
H(1,1) = PARAM(2)
H(2,1) = PARAM(3)
H(1,2) = PARAM(4)
H(2,2) = PARAM(5)
if PARAM(1) == -2.0
H = I (Identity matrix)
Item | Description |
---|---|
N | On entry, N specifies the number of elements in X and Y; unchanged on exit. |
X | Vector of dimension at least (1 + (N-1) * abs(INCX) ); on exit, modified as described above. |
INCX | On entry, INCX specifies the increment for the elements of X; INCX must be greater than 0; unchanged on exit. |
Y | Vector of dimension at least (1 + (N-1) * abs(INCY) ); on exit, modified as described above. |
INCY | On entry, INCY specifies the increment for the elements of Y; INCY must be greater than 0; unchanged on exit. |
PARAM | Vector of dimension (5); on entry, must be set as described above. Specifically, PARAM(1) is a flag and must have value of either 0.0, -1.0, 1.0, or 2.0; unchanged on exit. |