8x8 Matrix Transpose using AVX

[aw27]

Seriously though, how often would the average person need to transpose a matrix of any size?   

Not the average person but here most people are scientists 

[zedd151]

Not the average person but here most people are scientists 

Maybe I should have replaced 'average' in my post with 'normal'   :P

[Siekmanski]

Damn, look what I started.   

Clicking on "Show unread posts since last visit", there are FOUR matrix transpose threads active right now. And Marinus has just found a brand new VINSRTPS instruction. It's a mad place but I like it :icon_mrgreen:

My excuse is, it's described in the section header. 

[daydreamer]

Hi Zed  ,
I will have to think about a performance test then.  :t

now you calculator nerds,did anyone code a game on it?

[aw27]

Another approach, shorter and probably faster (untested). It requires AVX2 because uses the instruction VPGATHERDD (Gather Packed Dword Values Using Signed Dword).

Code Select Expand


; ************ TRANSPOSING CODE START ***********************
lea r8, invalues
mov ecx, 8
lea r9, outvalues
vmovdqa ymm0, YMMWORD PTR Index
@another:
vmovdqa ymm2, YMMWORD PTR _mask
VPGATHERDD ymm1, [r8+ymm0*1], ymm2
vmovdqa YMMWORD PTR [r9], ymm1
add r8, sizeof DWORD
add r9, 8*sizeof DWORD
loop @another
; ************ TRANSPOSING CODE END ************************


Code Select Expand


Transposing a 8x8 Matrix
Before:
row 0   1 2 3 4 5 6 7 8
row 1   9 10 11 12 13 14 15 16
row 2   17 18 19 20 21 22 23 24
row 3   25 26 27 28 29 30 31 32
row 4   33 34 35 36 37 38 39 40
row 5   41 42 43 44 45 46 47 48
row 6   49 50 51 52 53 54 55 56
row 7   57 58 59 60 61 62 63 64
After:
row 0   1 9 17 25 33 41 49 57
row 1   2 10 18 26 34 42 50 58
row 2   3 11 19 27 35 43 51 59
row 3   4 12 20 28 36 44 52 60
row 4   5 13 21 29 37 45 53 61
row 5   6 14 22 30 38 46 54 62
row 6   7 15 23 31 39 47 55 63
row 7   8 16 24 32 40 48 56 64