24 questions
2
votes
0
answers
61
views
Why is sequential indexing with fixed length stride slower in Estrin's method?
Preparing to make Estrin's method vectorisable I changed from normal linear indexing of the coefficients to bitreversed and restricted it to strictly powers of 2. Neither MSVC nor ICX can see how to ...
- 3,586
2
votes
0
answers
117
views
Why is Horner's method for evaluation faster than expected when loop unrolled for Polynomial lengths N<90?
I have spent some time trying to speed up code that uses Horner's method for evaluating modest length polynomials (N < 32). I have a solution using loop unrolling that works very well at -O2 or ...
- 3,586
2
votes
2
answers
119
views
Estrin polynomial evaluation - Intel ICX strange slowdown for lengths 16N-1
Porting what I believe to be working code for a radix-2 Estrin polynomial evaluation scheme to the Intel ICX 2024 compiler I am seeing a slowdown for a handful of polynomial lengths just below 16*N (...
- 3,586
1
vote
0
answers
70
views
mathcalls.h unknown type error when compiling using icx
I am compiling Wine on Linux using Intel LLVM compiler and I get many errors like these -
In file included from dlls/win32u/bitmap.c:33:
In file included from dlls/win32u/ntgdi_private.h:25:
In file ...
2
votes
1
answer
370
views
Intel ICX C++ compiler often generates slower code
We are trying to switch from the old Intel icc/icl compiler to the new icx compiler. After seeing a substantial performance degradation (in the order of 30%), and trying all the optimization options ...
- 41
2
votes
0
answers
551
views
Symbol clashes (Error LNK2005 frexp already defined in libmmt.lib(frexp_iface_c99.obj)) with Intel icx compiler inside VS2022 in debug mode
I'm test building a C++20 project and I ran into a linker error after upgrading the Windows SDK from version 10.0.22621.0 to 10.0.26100.0. The description given by the linker on VS2022 (17.10.3) is &...
- 21
2
votes
2
answers
62
views
Attempting to call a C function from python using ctypes and an icx-compiled dll file on Windows, but no functions are found
I have a c file display.c
#include <stdio.h>
void display()
{
printf("Hello, World!");
}
I turn it into a dll file with the following two lines:
icx.exe /c /EHsc display.c
xilink ...
- 749
1
vote
0
answers
67
views
Why does isnan() sometimes slowdown badly on ICX compiler?
I found a slowdown quirk on the Intel ICX compiler 2023 which goes some way to explaining my peculiar benchmark timings reported in earlier questions. I have what and how but don't understand why the ...
- 3,586
5
votes
0
answers
163
views
Dramatic slowdown of AVX2 code benchmarking sqrt, sin, cos depending on total string length - why?
Intel 2022 ICX compiler with AVX2 code generation and maximum optimisation shows a curious 30x slowdown when text string length in a printf is altered by a single character. How? Why? This is a much ...
- 3,586
3
votes
2
answers
205
views
Why do some x64 compilers not inline fmin/fminf?
I have been benchmarking some fast numerical code on various compilers recently and was struck by a systematic variation in the speed with certain compilers at maximum optimisation -O2 and AVX/AVX2 ...
- 3,586
3
votes
1
answer
264
views
Nan problem with Intel 2022 compiler using AVX2 & /fp:fast
I was playing with a test harness described in another post by @njaffa to try and make a faster more accurate erfc() function when I hit a peculiar bug that I am still unable to understand fully and ...
- 3,586
2
votes
0
answers
75
views
What does ICX do for 605.mcf_s of SPEC2017?
Recently I'm working on optimizing GCC for SPEC2017. And I found out that ICX runs two times faster on 605.mcf_s than GCC.
After a period of research, I've found that ICX has done a few things: fully ...
- 113
0
votes
0
answers
98
views
cob1904510_0.c:(.text+0x3b): relocation truncated to fit: R_X86_64_PC32 against `.bss'
Getting this error during linking. In this project, we have GnuCOBOL and C codes, so all objects are created using respective compilers but all linking are done using intel's icx compiler only. While ...
2
votes
1
answer
1k
views
Macro to check if I am running MSVC or Intel compiler
I am using the newest Visual Studio 2022 and also installed the Intel C++ compiler.
When I just write a simple main() to print the values of the macros MSC_VER and __INTEL_LLVM_COMPILER,
I get
...
- 311
0
votes
1
answer
2k
views
How to install older versions of Intel c++ compiler using apt
I want to install Intel C++ compiler version 17, 18, 19 using apt package management tool.
I searched on the official Intel website, but i can't find how to install older versions.
There are ...
- 147