# SETCONTROLFPQQ

Portability Subroutine: Sets the value of the floating-point processor control word.

## Module

USE IFPORT

CALL SETCONTROLFPQQ (controlword)

controlword | (Input) INTEGER(2). Floating-point processor control word.

The floating-point control word specifies how various exception conditions are handled by the floating-point math processor, sets the floating-point precision, and specifies the floating-point rounding mechanism used.

The control word can be any of the following constants (defined in `IFPORT.F90`):

Parameter name | Hex value | Description
--- | --- | ---
FPCW$MCW_IC | Z'1000' | Infinity control mask
FPCW$AFFINE | Z'1000' | Affine infinity
FPCW$PROJECTIVE | Z'0000' | Projective infinity
FPCW$MCW_PC | Z'0300' | Precision control mask
FPCW$64 | Z'0300' | 64-bit precision
FPCW$53 | Z'0200' | 53-bit precision
FPCW$24 | Z'0000' | 24-bit precision
FPCW$MCW_RC | Z'0C00' | Rounding control mask
FPCW$CHOP | Z'0C00' | Truncate
FPCW$UP | Z'0800' | Round up
FPCW$DOWN | Z'0400' | Round down
FPCW$NEAR | Z'0000' | Round to nearest
FPCW$MCW_EM | Z'003F' | Exception mask
FPCW$INVALID | Z'0001' | Allow invalid numbers
FPCW$DENORMAL | Z'0002' | Allow subnormals (very small numbers)
FPCW$SUBNORMAL | Z'0002' | Allow subnormals (very small numbers)
FPCW$ZERODIVIDE | Z'0004' | Allow divide by zero
FPCW$OVERFLOW | Z'0008' | Allow overflow
FPCW$UNDERFLOW | Z'0010' | Allow underflow
FPCW$INEXACT | Z'0020' | Allow inexact precision

An exception is disabled if its control bit is set to 1. An exception is enabled if its control bit is cleared to 0.

Setting the floating-point precision and rounding mechanism can be useful if you are reusing old code that is sensitive to the floating-point precision standard used and you want to get the same results as on the old machine.

You can use GETCONTROLFPQQ to retrieve the current control word and SETCONTROLFPQQ to change the control word. Most users do not need to change the default settings. If you need to change the control word, always use SETCONTROLFPQQ to make sure that special routines handling floating-point stack exceptions and abnormal propagation work correctly.

### Note

The Intel® Fortran exception handler allows for software masking of invalid operations, but does not allow the math chip to mask them. If you choose to use the software masking, be aware that this can affect program performance if you compile code written for Intel Fortran with another compiler.

## Example

     USE IFPORT
     INTEGER(2) status, control, controlo
     CALL GETCONTROLFPQQ(control)
     WRITE (*, 9000) 'Control word: ', control
     !     Save old control word
     controlo = control
     !     Clear all flags
     control = control .AND. Z'0000'
     !     Set new control to round up
     control = control .OR. FPCW$UP
     CALL SETCONTROLFPQQ(control)
     CALL GETCONTROLFPQQ(control)
     WRITE (*, 9000) 'Control word: ', control
     9000 FORMAT (1X, A, Z4)
     END

Parent topic: S

## See Also

GETCONTROLFPQQ
GETSTATUSFPQQ
LCWRQQ
SCWRQQ
CLEARSTATUSFPQQ