setmode

Sets a new mode for VM functions according to the mode parameter and returns the previous VM mode.

Syntax

uint64_t set_mode(queue &exec_queue, uint64_t new_mode)

Description

The set_mode function sets a new mode for VM functions according to the new_mode parameter and returns the previous VM mode. The mode change has a global effect on all the VM functions within a thread.

The mode parameter is designed to control accuracy and handling of denormalized numbers. You can obtain all other possible values of the mode parameter using bitwise OR ( | ) operation to combine one value for handling of denormalized numbers.

The mode::ftzdazon is specifically designed to improve the performance of computations that involve denormalized numbers at the cost of reasonable accuracy loss. This mode changes the numeric behavior of the functions: denormalized input values are treated as zeros (DAZ = denormals-are-zero) and denormalized results are flushed to zero (FTZ = flush-to-zero). Accuracy loss may occur if input and/or output values are close to denormal range.

Value of mode	Description
Accuracy Control
mode::ha	High accuracy versions of VM functions.
mode::la	Low accuracy versions of VM functions.
mode::ep	Enhanced performance accuracy versions of VM functions.
Denormalized Numbers Handling Control
mode::ftzdazon	Faster processing of denormalized inputs is enabled.
mode::ftzdazoff	Faster processing of denormalized inputs is disabled.
Other
mode::not_defined	VM status not defined.

The default value of the mode parameter is:

mode::ha | mode::ftdazoff

Input Parameters

exec_queue

The queue where the routine should be executed.

new_mode

Specifies the VM mode to be set.

Output Parameters

return value (old_mode)

Specifies the former VM mode.

Example

oldmode = set_mode (exec_queue , mode::la);
oldmode = set_mode (exec_queue , mode::ep | mode::ftzdazon);

Parent topic: VM Service Functions