hi,
when i do the diff
// Compute diff int32x4_t diff1_4 = vabsq_s32(vsubq_s32(A, B));
I got 4 result. One for each test (A1,B1)(A2,B2)(A3,B3) and (A4,B4)
And than i have to do the comparaison
uint32x4_t mask1_4 = vcltq_s32(diff1_4, X);
So in "uint32x4_t mask1_4" i got the comparaison for each test, so 4 résult.
the answer on post "SIMD help for exemple" was to use
if (vmaxvq_u32(mask1_4) > 0) { ... }
I thinks my sentence was confuse in the previous post. I wrote
" if (mask1_4[0] > 0 && mask1_4[1] > 0) and if (mask1_4[2] > 0 && mask1_4[3] > 0) "
but it is not if( mask1_4[0] > 0 && mask1_4[1] > 0 && mask1_4[2] > 0 && mask1_4[3] > 0) )
i need to do 2 test
if (mask1_4[0] > 0 && mask1_4[1] > 0){
process data1
}
if (mask1_4[2] > 0 && mask1_4[3] > 0){
process data2
I think that vmaxvq_u32(mask1_4) will check all the comparaison. like
if( mask1_4[0] > 0 && mask1_4[1] > 0 && mask1_4[2] > 0 && mask1_4[3] > 0 )
PS: i think i should have post it in the old post
hterrolle said:t look like it is a problem of printf using signed and unsigned integer type.
You need to use "%d" for signed and "%u" for unsigned.
hterrolle said:uint32x4_t mask1_4 = vcltq_u32(diff1_4, constseuil);
In your original code your diff1_4 is signed and you were using "vcltq_s32" which is the signed compare, so the compare should be correct for signed values.
The result of all of the NEON compare functions is not really meaningful as a number - it's just a bitmask with all bits in a lane set to 1 if the compare, like vcltq_s32, passed and zero if it failed. Given it's not expected to be interpreted as a number, the result is always uint32_t no matter what the original compare data type was, and the only comparison that matters is whether that mask is zero or non-zero.
i just read your response when i was writting my. ;))
sorry for the prévious post. I anderstoud the problem. Using %u rather than %d give me the response.
it look like -1 is converted to unsigned int during the < -1
so -1 = 4294967295 and -2 = 4294967294 so 4294967294 is < to 4294967295.
but i is really confusing.
Thanks very much for your answer. I was confuse at the begining of the day. Now i can go back to my program calmly, ;))
have a good day.
sorry again, i just forgot to ask. what is the best in term of performance.
extract and compare
uint32x2_t mask1_4_01 = vget_low_u32(mask1_4); then if ( vminv_u32(mask1_4_01) > 0)
or
if (mask1_4[0] > 0 && mask1_4[1] > 0 ){
I think it is good for me then.
and thanks again.