Edit - Stack Overflow

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

Rev

For a 3-vector sum, I'd need to set the fourth component to zero first. What's the fastest way to do that? I'm tending towards "load mask, andps" - is there a fast way to mask out an element?

FeepingCreature
– FeepingCreature

2011-08-09 16:19:22 +00:00
Commented Aug 9, 2011 at 16:19
I don't see any faster way than ANDPS, which is one instruction (the mask being constant of course).

Paul R
– Paul R

2011-08-09 16:35:29 +00:00
Commented Aug 9, 2011 at 16:35
@FeepingCreature __m128 vector3 = _mm_castps_si128(_mm_castsi128_ps(_mm_srli_si128(vector4, 4))); - this may be faster than masking depending on whether your mask is already loaded from memory

awdz9nld
– awdz9nld

2013-12-20 20:53:19 +00:00
Commented Dec 20, 2013 at 20:53
Hi, How does it compare to @Peter Cordes SSE3 Solution? Thank You.

Royi
– Royi

2017-02-06 19:55:27 +00:00
Commented Feb 6, 2017 at 19:55
1

@Royi: see Peter's comments in his answer, under the heading "SSE3 optimizing for code-size".

Paul R
– Paul R

2017-02-06 23:37:13 +00:00
Commented Feb 6, 2017 at 23:37

Add a comment |

Correct minor typos or mistakes
Clarify meaning without changing it
Add related resources or links
Always respect the author’s intent
Don’t use edits to reply to the author

create code fences with backticks ` or tildes ~
```
like so
```
add language identifier to highlight code
```python
def function(foo):
print(foo)
```
put returns between paragraphs
for linebreak add 2 spaces at end
_italic_ or **bold**
indent code by 4 spaces
backtick escapes `like _so_`
quote by placing > at start of line
to make links (use https whenever possible)

<https://example.com>

[example](https://example.com)

<a href="https://example.com">example</a>

formatting help »
answering help »

Collectives™ on Stack Overflow