hameeza ahmed via llvm-dev
2017-Jul-01 22:33 UTC
[llvm-dev] Jacobi 5 Point Stencil Code not Vectorizing
I am able to vectorize it with the following code;
#include <stdio.h>
#define N 100351
// This function computes 2D-5 point Jacobi stencil
void stencil(int a[][N], int b[][N])
{
int i, j, k;
for (k = 0; k < N; k++) {
for (i = 1; i <= N-2; i++)
for (j = 1; j <= N-2; j++)
b[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] + a[i][j-1] +
a[i][j+1]);
for (i = 1; i <= N-2; i++)
for (j = 1; j <= N-2; j++)
a[i][j] = b[i][j];
}
}
I removed restrict over here.
On Sun, Jul 2, 2017 at 3:11 AM, hameeza ahmed <hahmed2305 at gmail.com>
wrote:
> further i modified the code to the following;
>
> #include <stdio.h>
> #define N 100351
>
> // This function computes 2D-5 point Jacobi stencil
> void stencil(int a[restrict][N], int b[restrict][N])
> {
> int i, j, k;
> for (k = 0; k < N; k++) {
> for (i = 1; i <= N-2; i++)
> for (j = 1; j <= N-2; j++)
> b[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] + a[i][j-1] +
> a[i][j+1]);
>
> for (i = 1; i <= N-2; i++)
> for (j = 1; j <= N-2; j++)
> a[i][j] = b[i][j];
>
> }
> }
>
> but still no vectorization in IR. Also, when I set vector width
> explicitly to 64, it gives the following error:
>
> remark: <unknown>:0:0: loop not vectorized: call instruction cannot
be
> vectorized
> remark: <unknown>:0:0: loop not vectorized: value that could not be
> identified as reduction is used outside the loop
>
> I need serious help on this. Please guide me.
>
> On Sun, Jul 2, 2017 at 1:54 AM, hameeza ahmed <hahmed2305 at
gmail.com>
> wrote:
>
>> Does it happen due to loop carried dependence? if yes what is the
>> solution to vectorize such codes?
>>
>>
>> please reply. i m waiting.
>>
>> On Jul 1, 2017 12:30 PM, "hameeza ahmed" <hahmed2305 at
gmail.com> wrote:
>>
>>> I even tried polly but still my llvm IR does not contain vector
>>> instructions. i used the following command;
>>>
>>> clang -S -emit-llvm stencil.c -march=knl -O3 -mllvm -polly -mllvm
>>> -polly-vectorizer=stripmine -o stencil_poly.ll
>>>
>>> Please specify what is wrong with my code?
>>>
>>>
>>> On Sat, Jul 1, 2017 at 4:08 PM, hameeza ahmed <hahmed2305 at
gmail.com>
>>> wrote:
>>>
>>>> Hello,
>>>>
>>>> I am trying to vectorize following stencil code;
>>>>
>>>> #include <stdio.h>
>>>> #define N 100351
>>>>
>>>> // This function computes 2D-5 point Jacobi stencil
>>>> void stencil(int a[restrict][N])
>>>> {
>>>> int i, j, k;
>>>> for (k = 0; k < 100; k++)
>>>> { for (i = 1; i <= N-2; i++)
>>>> { for (j = 1; j <= N-2; j++)
>>>> { a[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] +
>>>> a[i][j-1] + a[i][j+1]);
>>>> }
>>>> }
>>>> }}
>>>>
>>>> I have used the following commands
>>>>
>>>> clang -S -emit-llvm stencil.c -march=knl -O3 -mllvm
>>>> -disable-llvm-optzns -o stencil.ll
>>>>
>>>> opt -S -O3 stencil.ll -o stencil_o3.ll
>>>>
>>>> llc -x86-asm-syntax=intel stencil_o3.ll -o stencil.s
>>>>
>>>> But the code is not vectorized. It still uses the scalar
instructions;
>>>>
>>>> Please correct me.
>>>>
>>>> Thank You
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20170702/e04385fa/attachment.html>
Hal Finkel via llvm-dev
2017-Jul-02 08:28 UTC
[llvm-dev] Jacobi 5 Point Stencil Code not Vectorizing
On 07/01/2017 05:33 PM, hameeza ahmed wrote:> I am able to vectorize it with the following code; > > #include <stdio.h> > #define N 100351 > // This function computes 2D-5 point Jacobi stencil > void stencil(int a[][N], int b[][N]) > { > int i, j, k; > for (k = 0; k < N; k++) { > for (i = 1; i <= N-2; i++) > for (j = 1; j <= N-2; j++) > b[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] + a[i][j-1] + > a[i][j+1]); > > for (i = 1; i <= N-2; i++) > for (j = 1; j <= N-2; j++) > a[i][j] = b[i][j]; > } > } > > I removed restrict over here.That seems odd. Can you please file a bug report? -Hal> > On Sun, Jul 2, 2017 at 3:11 AM, hameeza ahmed <hahmed2305 at gmail.com > <mailto:hahmed2305 at gmail.com>> wrote: > > further i modified the code to the following; > > #include <stdio.h> > #define N 100351 > // This function computes 2D-5 point Jacobi stencil > void stencil(int a[restrict][N], int b[restrict][N]) > { > int i, j, k; > for (k = 0; k < N; k++) { > for (i = 1; i <= N-2; i++) > for (j = 1; j <= N-2; j++) > b[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] + a[i][j-1] + > a[i][j+1]); > > for (i = 1; i <= N-2; i++) > for (j = 1; j <= N-2; j++) > a[i][j] = b[i][j]; > } > } > > but still no vectorization in IR. Also, when I set vector width > explicitly to 64, it gives the following error: > > remark: <unknown>:0:0: loop not vectorized: call instruction > cannot be vectorized > remark: <unknown>:0:0: loop not vectorized: value that could not > be identified as reduction is used outside the loop > > I need serious help on this. Please guide me. > > On Sun, Jul 2, 2017 at 1:54 AM, hameeza ahmed > <hahmed2305 at gmail.com <mailto:hahmed2305 at gmail.com>> wrote: > > Does it happen due to loop carried dependence? if yes what is > the solution to vectorize such codes? > > > please reply. i m waiting. > > On Jul 1, 2017 12:30 PM, "hameeza ahmed" <hahmed2305 at gmail.com > <mailto:hahmed2305 at gmail.com>> wrote: > > I even tried polly but still my llvm IR does not contain > vector instructions. i used the following command; > > clang -S -emit-llvm stencil.c -march=knl -O3 -mllvm > -polly -mllvm -polly-vectorizer=stripmine -o stencil_poly.ll > > Please specify what is wrong with my code? > > > On Sat, Jul 1, 2017 at 4:08 PM, hameeza ahmed > <hahmed2305 at gmail.com <mailto:hahmed2305 at gmail.com>> wrote: > > Hello, > > I am trying to vectorize following stencil code; > > #include <stdio.h> > #define N 100351 > // This function computes 2D-5 point Jacobi stencil > void stencil(int a[restrict][N]) > { > int i, j, k; > for (k = 0; k < 100; k++) > { for (i = 1; i <= N-2; i++) > { for (j = 1; j <= N-2; j++) > { a[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] + > a[i][j-1] + a[i][j+1]); > } > } > }} > > I have used the following commands > > clang -S -emit-llvm stencil.c -march=knl -O3 -mllvm > -disable-llvm-optzns -o stencil.ll > > opt -S -O3 stencil.ll -o stencil_o3.ll > > llc -x86-asm-syntax=intel stencil_o3.ll -o stencil.s > > But the code is not vectorized. It still uses the > scalar instructions; > > Please correct me. > > Thank You > > > > > > >-- Hal Finkel Lead, Compiler Technology and Programming Languages Leadership Computing Facility Argonne National Laboratory -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170702/a00748f2/attachment.html>
hameeza ahmed via llvm-dev
2017-Jul-02 08:47 UTC
[llvm-dev] Jacobi 5 Point Stencil Code not Vectorizing
but now it works fine with mentioned code. On Sun, Jul 2, 2017 at 1:28 PM, Hal Finkel <hfinkel at anl.gov> wrote:> > On 07/01/2017 05:33 PM, hameeza ahmed wrote: > > I am able to vectorize it with the following code; > > #include <stdio.h> > #define N 100351 > > // This function computes 2D-5 point Jacobi stencil > void stencil(int a[][N], int b[][N]) > { > int i, j, k; > for (k = 0; k < N; k++) { > for (i = 1; i <= N-2; i++) > for (j = 1; j <= N-2; j++) > b[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] + a[i][j-1] + > a[i][j+1]); > > for (i = 1; i <= N-2; i++) > for (j = 1; j <= N-2; j++) > a[i][j] = b[i][j]; > > } > } > > I removed restrict over here. > > > That seems odd. Can you please file a bug report? > > -Hal > > > > On Sun, Jul 2, 2017 at 3:11 AM, hameeza ahmed <hahmed2305 at gmail.com> > wrote: > >> further i modified the code to the following; >> >> #include <stdio.h> >> #define N 100351 >> >> // This function computes 2D-5 point Jacobi stencil >> void stencil(int a[restrict][N], int b[restrict][N]) >> { >> int i, j, k; >> for (k = 0; k < N; k++) { >> for (i = 1; i <= N-2; i++) >> for (j = 1; j <= N-2; j++) >> b[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] + a[i][j-1] + >> a[i][j+1]); >> >> for (i = 1; i <= N-2; i++) >> for (j = 1; j <= N-2; j++) >> a[i][j] = b[i][j]; >> >> } >> } >> >> but still no vectorization in IR. Also, when I set vector width >> explicitly to 64, it gives the following error: >> >> remark: <unknown>:0:0: loop not vectorized: call instruction cannot be >> vectorized >> remark: <unknown>:0:0: loop not vectorized: value that could not be >> identified as reduction is used outside the loop >> >> I need serious help on this. Please guide me. >> >> On Sun, Jul 2, 2017 at 1:54 AM, hameeza ahmed <hahmed2305 at gmail.com> >> wrote: >> >>> Does it happen due to loop carried dependence? if yes what is the >>> solution to vectorize such codes? >>> >>> >>> please reply. i m waiting. >>> >>> On Jul 1, 2017 12:30 PM, "hameeza ahmed" <hahmed2305 at gmail.com> wrote: >>> >>>> I even tried polly but still my llvm IR does not contain vector >>>> instructions. i used the following command; >>>> >>>> clang -S -emit-llvm stencil.c -march=knl -O3 -mllvm -polly -mllvm >>>> -polly-vectorizer=stripmine -o stencil_poly.ll >>>> >>>> Please specify what is wrong with my code? >>>> >>>> >>>> On Sat, Jul 1, 2017 at 4:08 PM, hameeza ahmed <hahmed2305 at gmail.com> >>>> wrote: >>>> >>>>> Hello, >>>>> >>>>> I am trying to vectorize following stencil code; >>>>> >>>>> #include <stdio.h> >>>>> #define N 100351 >>>>> >>>>> // This function computes 2D-5 point Jacobi stencil >>>>> void stencil(int a[restrict][N]) >>>>> { >>>>> int i, j, k; >>>>> for (k = 0; k < 100; k++) >>>>> { for (i = 1; i <= N-2; i++) >>>>> { for (j = 1; j <= N-2; j++) >>>>> { a[i][j] = 0.25 * (a[i][j] + a[i-1][j] + a[i+1][j] + >>>>> a[i][j-1] + a[i][j+1]); >>>>> } >>>>> } >>>>> }} >>>>> >>>>> I have used the following commands >>>>> >>>>> clang -S -emit-llvm stencil.c -march=knl -O3 -mllvm >>>>> -disable-llvm-optzns -o stencil.ll >>>>> >>>>> opt -S -O3 stencil.ll -o stencil_o3.ll >>>>> >>>>> llc -x86-asm-syntax=intel stencil_o3.ll -o stencil.s >>>>> >>>>> But the code is not vectorized. It still uses the scalar instructions; >>>>> >>>>> Please correct me. >>>>> >>>>> Thank You >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >> > > -- > Hal Finkel > Lead, Compiler Technology and Programming Languages > Leadership Computing Facility > Argonne National Laboratory > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170702/66560622/attachment.html>