Convert REAL4 to HALF

[aw27]

As a follow up of this, I present here 2 methods of converting 1 REAL4 to 1 HALF, the VCVTPS2PH method and the no-VCVTPS2PH method.
The first one is the best but may not work on all computers.
I compare if the result obtained from both methods yields the same result. It does  (in this case)

Code Select Expand


HALF values are equal


BTW, I have not figured out yet know how to print a HALF (without converting it back of course). Anyone?

[Siekmanski]

HALF values are equal  :t

[jj2007]

On my Core i5-2450M, vcvtps2ph xmm1, xmm0 is an illegal instruction.

[aw27]

On my Core i5-2450M, vcvtps2ph xmm1, xmm0 is an illegal instruction.

You need an Ivy Bridge or later.

[FORTRANS]

Hi,

   Intel Core i3 4005U.

HALF values are equal

Steve N.

[hutch--]

Haswell E/EP

HALF values are equal

[daydreamer]

As a follow up of this, I present here 2 methods of converting 1 REAL4 to 1 HALF, the VCVTPS2PH method and the no-VCVTPS2PH method.
The first one is the best but may not work on all computers.
I compare if the result obtained from both methods yields the same result. It does  (in this case)

BTW, I have not figured out yet know how to print a HALF (without converting it back of course). Anyone?

doesnt work
I Think its more interesting to be able to store twice the amount meshes in a demo
isnt it actually what you get from importing 3d files,double values in ascii->half's much smaller?

[aw27]

Now, I will not use the modern instructions, some people still has pre- Ivy Bridge computers, and will print the HALF by converting it back and consider 4 significant digits (it has 3/4 significant digits), by luck in this case the 4th digit is still valid.

Code Select Expand


REAL4 Value=1.234567
HALF Value=1.234


@daydream
All depends on what you have in mind

[Siekmanski]

Nice 

Daydreamer, to compress vertex data, use "vertex subdivision" and convert the data to half floats  ( the files will be incredible small ).

[daydreamer]

Now, I will not use the modern instructions, some people still has pre- Ivy Bridge computers, and will print the HALF by converting it back and consider 4 significant digits (it has 3/4 significant digits), by luck in this case the 4th digit is still valid.

Code Select Expand


REAL4 Value=1.234567
HALF Value=1.234


@daydream
All depends on what you have in mind

Would be nice to add aircraft meshes and other meshes as small  together in my project with procedural terrain making