ptx

Is it possible to put assembly instructions into CUDA code?

由 若如初见. 提交于 2019-12-14 00:31:17
问题 I want to use assembly code in CUDA C code in order to reduce expensive executions as we do using asm in c programming. Is it possible? 回答1: No, you can't, there is nothing like the asm constructs from C/C++. What you can do is tweak the generated PTX assembly and then use it with CUDA. See this for an example. But for GPUs, assembly optimizations are NOT necessary, you should do other optimizations first, such as memory coalescency and occupancy. See the CUDA Best Practices guide for more

How to prevent FTZ for a single line in CUDA

由 江枫思渺然 提交于 2019-12-12 13:33:26
问题 I am working on a particle code where flushing-to-zero is extensively used to extract performance. However there is a single floating point comparison statement that I do not wish to be flushed. One solution is to use inline PTX, but it introduces unnecessary instructions since there is no boolean type, but just predicate registers, in PTX: C++ code: float a, b; if ( a < b ) do_something; // compiles into SASS: // FSETP.LT.FTZ.AND P0, PT, A, B, PT; // @P0 DO_SOMETHING PTX: float a, b; uint p;

Should I look into PTX to optimize my kernel? If so, how?

由 筅森魡賤 提交于 2019-12-12 10:37:03
问题 Do you recommend reading your kernel's PTX code to find out to optimize your kernels further? One example: I read, that one can find out from the PTX code if the automatic loop unrolling worked. If this is not the case, one would have to unroll the loops manually in the kernel code. Are there other use-cases for the PTX code? Do you look into your PTX code? Where can I find out how to be able to read the PTX code CUDA generates for my kernels? 回答1: The first point to make about PTX is that it

Cuda PTX registers declaration and using

由 本秂侑毒 提交于 2019-12-12 01:46:34
问题 I am trying to reduce number of using registers in my kernel, so I am decide to try inline PTX. This kernel: #define Feedback(a, b, c, d, e) d^e^(a&c)^(a&e)^(b&c)^(b&e)^(c&d)^(d&e)^(a&d&e)^(a&c&e)^(a&b&d)^(a&b&c) __global__ void Test(unsigned long a, unsigned long b, unsigned long c, unsigned long d, unsigned long e, unsigned long f, unsigned long j, unsigned long h, unsigned long* res) { res[0] = Feedback( a, b, c, d, e ); res[1] = Feedback( b, c, d, e, f ); res[2] = Feedback( c, d, e, f, j

Syntax on inline PTX code for CUDA

由 孤街浪徒 提交于 2019-12-11 13:45:59
问题 As written in Nvidia's Inline PTX Assembly document, the grammar for using inline assembly is: asm("temp_string" : "constraint"(output) : "constraint"(input)); Here are two examples: asm("vadd.s32.s32.s32 %0, %1.h0, %2.h0;" : "=r"(v) : "r"(a), "r"(b)); asm("vadd.u32.u32.u32 %0.b0, %1, %2, %3;" : "=r"(v) : "r"(a), "r"(b), "r"(z)); In both examples, there are parameters such as: h0 or b0 follow the %n . I looked through CUDA's official document and didn't find anything concerns about the

c++filt not aggressive enough for some of the mangled names in PTX files

由 大兔子大兔子 提交于 2019-12-11 04:14:42
问题 I'm filtering my compiled PTX through c++filt, but it only demangles some of the names/labels and leaves some as-is. For example, this: func (.param .b32 func_retval0) _ZN41_INTERNAL_19_gather_bits_cpp1_ii_56538e7c6__shflEiii( .param .b32 _ZN41_INTERNAL_19_gather_bits_cpp1_ii_56538e7c6__shflEiii_param_0, .param .b32 _ZN41_INTERNAL_19_gather_bits_cpp1_ii_56538e7c6__shflEiii_param_1, .param .b32 _ZN41_INTERNAL_19_gather_bits_cpp1_ii_56538e7c6__shflEiii_param_2 ) is demangled as this: .func (

CUDA/PTX 32-bit vs. 64-bit

由 浪尽此生 提交于 2019-12-05 06:02:51
CUDA compilers have options for producing 32-bit or 64-bit PTX. What is the difference between these? Is it like for x86, NVidia GPUs actually have 32-bit and 64-bit ISAs? Or is it related to host code only? Robert Crovella Pointers are certainly the most obvious difference . 64 bit machine model enables 64-bit pointers. 64 bit pointers enable a variety of things, such as address spaces larger than 4GB, and unified virtual addressing . Unified virtual addressing in turn enables other things, such as GPUDirect Peer-to-Peer . The CUDA IPC API also depends on 64 bit machine model. The x64 ISA is

Is it possible to put assembly instructions into CUDA code?

由 谁都会走 提交于 2019-12-05 05:16:29
I want to use assembly code in CUDA C code in order to reduce expensive executions as we do using asm in c programming. Is it possible? Matias Valdenegro No, you can't, there is nothing like the asm constructs from C/C++. What you can do is tweak the generated PTX assembly and then use it with CUDA. See this for an example. But for GPUs, assembly optimizations are NOT necessary, you should do other optimizations first, such as memory coalescency and occupancy. See the CUDA Best Practices guide for more information. Since CUDA 4.0, inline PTX is supported by the CUDA toolchain. There is a

Confusion with CUDA PTX code and register memory

由 旧时模样 提交于 2019-12-04 20:47:30
问题 :) While I was trying to manage my kernel resources I decided to look into PTX but there are a couple of things that I do not understand. Here is a very simple kernel I wrote: __global__ void foo(float* out, float* in, uint32_t n) { uint32_t idx = blockIdx.x * blockDim.x + threadIdx.x; uint32_t one = 5; out[idx] = in[idx]+one; } Then I compiled it using: nvcc --ptxas-options=-v -keep main.cu and I got this output on the console: ptxas info : 0 bytes gmem ptxas info : Compiling entry function

Funnel shift - what is it?

由 百般思念 提交于 2019-12-04 18:05:07
问题 When reading through CUDA 5.0 Programming Guide I stumbled on a feature called "Funnel shift" which is present in 3.5 compute-capable device, but not 3.0. It contains an annotation "see reference manual", but when I search for the "funnel shift" term in the manual, I don't find anything. I tried googling for it, but only found a mention on http://www.cudahandbook.com, in the chapter 8: 8.2.3 Funnel Shift (SM 3.5) GK110 added a 64-bit “funnel shift” instruction that may be accessed with the
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