POPCNT(3I) Last changed: 1-6-98
NAME
_popcnt, POPCNT - Counts number of set bits
SYNOPSIS
C/C++:
#include <intrinsics.h>
int _popcnt (long i);
Fortran:
POPCNT ([I=]i)
IMPLEMENTATION
C/C++: UNICOS and UNICOS/mk systems
Fortran: UNICOS, UNICOS/mk, and IRIX systems
STANDARDS
C/C++: Cray Research extension
Fortran: CF90 and MIPSpro 7 Fortran 90 compiler extension to Fortran
90
C/C++ DESCRIPTION
The _popcnt function returns the number of bits set to 1 (the
population count) in argument i.
FORTRAN DESCRIPTION
This intrinsic function counts the number of bits set in the argument.
It accepts the following argument:
i A Boolean, integer, real, or Cray pointer value. On IRIX
systems, i cannot be declared as REAL(KIND=16).
POPCNT is an elemental function. The name of this intrinsic cannot be
passed as an argument.
C/C++ NOTES
Because _popcnt is an intrinsic function, no externally visible
library function is available for it. The compiler generates inline
code to produce the result.
FORTRAN NOTES
The bit representation of the logical data type is not consistent
among Cray Research systems. For further details, see your compiler's
reference manuals.
FORTRAN RETURN VALUES
POPCNT returns a value of type integer.
EXAMPLES
Fortran: The following section of Fortran code shows the POPCNT
function used with an argument of type integer. The bit pattern of
the argument and the value of the result are also given. For
simplicity, a 16-bit object is used.
INTEGER I1, I2
...
I2 = POPCNT(I1)---------------------------------------------------------------
| 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 1 | 0 |
---------------------------------------------------------------
I1
The POPCNT function returns the value 6 to the integer variable I2.
SEE ALSO
A complete list of C/C++ intrinsic functions available on Cray
Research systems is in the Cray C/C++ Reference Manual, publication SR
-2179.
Intrinsic Procedures Reference Manual, publication SR-2138, for the
printed version of this man page.
