Technical Reference: Base Operating System and Extensions, Volume 2

ISAMAX, IDAMAX, ICAMAX, or IZAMAX Function

Finds the index of element having maximum absolute value.

BLAS Library (libblas.a)

INTEGER FUNCTION ISAMAX(N,X,INCX) INTEGER INCX, N REAL X(*)

INTEGER FUNCTION IDAMAX(N,X,INCX)
INTEGER INCX,N
DOUBLE PRECISION X(*)

INTEGER FUNCTION ICAMAX(N,X,INCX)
INTEGER INCX,N
COMPLEX X(*)

INTEGER FUNCTION IZAMAX(N,X,INCX)
INTEGER INCX,N
COMPLEX*16 X(*)

The ISAMAX, IDAMAX, ICAMAX, or IZAMAX function returns the index of element having maximum absolute value.

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) ); unchanged on exit.
INCX	On entry, INCX specifies the increment for the elements of X; unchanged on exit.

For values of N <= 0, a value of 0 is returned.