NAME

ddoti - Compute the indexed dot product.

SYNOPSIS

 DOUBLE PRECISION FUNCTION DDOTI(NZ, X, INDX, Y)

 DOUBLE PRECISION X(*), Y(*)
 INTEGER NZ
 INTEGER INDX(*)

 DOUBLE PRECISION FUNCTION DDOTI_64(NZ, X, INDX, Y)

 DOUBLE PRECISION X(*), Y(*)
 INTEGER*8 NZ
 INTEGER*8 INDX(*)

F95 INTERFACE DOUBLE PRECISION FUNCTION DOTI([NZ], X, INDX, Y)

 REAL(8), DIMENSION(:) :: X, Y
 INTEGER :: NZ
 INTEGER, DIMENSION(:) :: INDX

 DOUBLE PRECISION FUNCTION DOTI_64([NZ], X, INDX, Y)

 REAL(8), DIMENSION(:) :: X, Y
 INTEGER(8) :: NZ
 INTEGER(8), DIMENSION(:) :: INDX

DDOTI Compute the indexed dot product of a real sparse vector x stored in compressed form with a real vector y in full storage form.

 dot = 0
 do i = 1, n
   dot = dot + x(i) * y(indx(i))
 enddo

NZ (input): Number of elements in the compressed form. Unchanged on exit.
X (input): Vector in compressed form. Unchanged on exit.
INDX (input): Vector containing the indices of the compressed form. It is assumed that the elements in INDX are distinct and greater than zero. Unchanged on exit.
Y (input): Vector in full storage form. Only the elements corresponding to the indices in INDX will be accessed.