neon

问题 I have a lot of code that is based on open cv but there are many ways in which the Arm Compute library improves performance, so id like to integrate some arm compute library code into my project. Has anyone tried converting between the two corresponding Image structures? If so, what did you do? Or is there a way to share a pointer to the underlying data buffer without needing to copy image data and just set strides and flags appropriately? 回答1: I was able to configure an arm_compute::Image

问题 I want to compare 2 int8x8_t , From http://gcc.gnu.org/onlinedocs/gcc/ARM-NEON-Intrinsics.html we can get the description for vclt_s8 , but it does not tell us much details. `uint8x8_t vclt_s8 (int8x8_t, int8x8_t)` Form of expected instruction(s): vcgt.s8 d0, d0, d0 the return value uint8x8_t , it confuse me for I can not use if(vclt_s8(a, b)) to decide the first is smaller. Then suppose we have two int8x8_t : int8x8_t a and int8x8_t b , how do we know whether a is smaller? 回答1: You may find

问题 I want to process a large array of floating-point numbers on the ARM processor, using Neon technology to calculate them four at a time. Everything's fine for operations like add and multiply, but what do I do if my calculation goes into an IF block? Example: // In the non-vectorized original code, A is an array of many floating-point // numbers, which are calculated one at a time. Now they're packed // into a vector and processed four at a time ...calculate A... if (A > 10.f) { A = A+5.f; }

问题 TLTR For arm intrinsics, how do you feed a 128bit variable of type uint8x16_t into a function expecting uint16x8_t ? EXTENDED VERSION Context: I have a greyscale image, 1 byte per pixel. I want to downscale it by a factor 2x. For each 2x2 input box, I want to take the minimum pixel. In plain C, the code will look like this: for (int y = 0; y < rows; y += 2) { uint8_t* p_out = outBuffer + (y / 2) * outStride; uint8_t* p_in = inBuffer + y * inStride; for (int x = 0; x < cols; x += 2) { *p_out =

问题 I would like to realize if condition in armv8 NEON inline assembly code. In armv7 this was possible through checking overflow bit like this: VMRS r4, FPSCR BIC r4, r4, #(1<<27) VMSR FPSCR, r4 vtst.16 d30, d30, d30 vqadd.u16 d30, d30, d30 vmrs r4, FPSCR tst r4, #(1<<27) bne label1 But I am not able to achieve this in armv8 equivalent code. It seems that SQADD doesnt affect overflow bit in FPSR or I cannot check it like this. Is it possible or is there better approach how to skip long part of

问题 There is a big (~100 000) array of floating point variables, and there is a threshold (also floating point). The problem is that I have to compare each one variable from the array with a threshold, but NEON flags transfer takes a really long time (~20 cycles in accordance to a profiler). Is there any efficient way to compare these values? NOTE: As rounding error doesn't matter, I tried the following: float arr[10000]; float threshold; .... int a = arr[20]; // e.g. int t = threshold; if (t > a

问题 I have browsed the tutorial of eigen at https://eigen.tuxfamily.org/dox-devel/group__TutorialMatrixArithmetic.html it said "Note: for BLAS users worried about performance, expressions such as c.noalias() -= 2 * a.adjoint() * b; are fully optimized and trigger a single gemm-like function call." but how about computation like H.transpose() * H , because it's result is a symmetric matrix so it should only need half time as normal A*B, but in my test, H.transpose() * H spend same time as H

问题 I want to add 00 and 01 indices value of int64x2_t vector in neon . I am not able to find any pairwise-add instruction which will do this functionality . int64x2_t sum_64_2; //I am expecting result should be.. //int64_t result = sum_64_2[0] + sum_64_2[1]; Is there any instruction in neon do to this logic. 回答1: You can write it in two ways. This one explicitly uses the NEON VADD.I64 instruction: int64x1_t f(int64x2_t v) { return vadd_s64 (vget_high_s64 (v), vget_low_s64 (v)); } and the

问题 I have successfully compiled and added FFMPEG to my android device. but it did not works in some device, which are don't have neon cpu (HTC v one ,Kyocera) can any one suggest me to make that work . I have used the following link to get the ffmpeg build Link .Used NDK 10 and platform as 4.6 来源： https://stackoverflow.com/questions/29160063/ffmpeg-android-not-worked-in-the-non-neon-cpus

问题 I am trying to cross-compil FFTW 3.3.3 for cortex-a15 ARM processor with neon support but I get this error: /tmp/ccsNpqyK.s: Assembler messages: /tmp/ccsNpqyK.s:1035: Error: co-processor offset out of range Here is my configuration: ./configure --prefix=/usr/fftw_3_float_neon_ARNDALE --with-slow-timer --host=arm-linux-gnueabi --target=arm-linux-gnueabi --enable-float --enable-neon "CC=/usr/bin/arm-linux-gnueabi-gcc-4.6 -mfloat-abi=softfp -mcpu=cortex-a15 -mtune=cortex-a15 -O3 -mfpu=neon