Assignment between restrict pointers "alpha" and "alpha_in" is not allowed. Only outer-to-inner scope assignments between restrict pointers are allowed. about blis HOT 8 CLOSED

Whether or not XLC is right, woe to he who ignores restrict warnings.

from blis.

Jeff,

Best thing to do in the short term is to insert a “#define restrict /* nothing */“ in the bli_config.h for bgq.

What’s going on below can be fixed by a couple of extra curly braces.

As an example, XLC will complain about:
int function( double* restrict a)
{
double* restrict b = a;
return 0;
}
because apparently local variables are in the same scope as function arguments.

But it won’t complain about:
int function( double* restrict a)
{
{
double* restrict b = a;
return 0;
}
}
because this creates an inner scope where b is defined, and “outer to inner assignments” are allowed.

So basically to use restrict pointers on bgq, BLIS just needs a ton of extra curly braces.

-Tyler

On Apr 3, 2014, at 3:33 PM, Jeff Hammond [email protected] wrote:

XLC is the only compiler I've ever seen that gives these warnings, but I think they are formally legit. On the other hand, they may be false positives in practice.

[jhammond@vestalac1 blis]$ ./configure -p $HOME/BLIS/bgq bgq && make -j32 && make install
configure: checking whether we need to update the version file.
configure: checking version file './version'.
configure: found '.git' directory; assuming git clone.
configure: executing git describe --tags.
configure: got back 0.1.1-14-gd531a24.
configure: truncating to 0.1.1-14.
configure: updating version file './version'.
configure: starting configuration of BLIS 0.1.1-14.
configure: configuring with 'bgq' configuration sub-directory.
configure: detected -p option; using install prefix '/home/jhammond/BLIS/bgq'.
configure: creating ./config.mk from ./build/config.mk.in
configure: creating ./obj/bgq
configure: creating ./obj/bgq/config
configure: creating ./obj/bgq/frame
configure: creating ./obj/bgq/testsuite
configure: creating ./lib/bgq
configure: mirroring ./config/bgq to ./obj/bgq/config
configure: mirroring ./frame to ./obj/bgq/frame
configure: creating makefile fragment in ./config/bgq
configure: creating makefile fragment in ./config/bgq/kernels
configure: creating makefile fragment in ./config/bgq/kernels/1
configure: creating makefile fragment in ./config/bgq/kernels/1f
configure: creating makefile fragment in ./config/bgq/kernels/3
configure: creating makefile fragment in ./frame
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configure: configured to build within top-level directory of source distribution.
Compiling config/bgq/kernels/1/bli_axpyv_opt_var1.c (NOTE: using flags for kernels)
Compiling frame/0/unzipsc/bli_unzipsc.c
Compiling frame/0/unzipsc/bli_unzipsc_check.c
Compiling frame/0/unzipsc/bli_unzipsc_unb_var1.c
Compiling frame/0/zipsc/bli_zipsc.c
Compiling frame/0/zipsc/bli_zipsc_check.c
Compiling frame/0/zipsc/bli_zipsc_unb_var1.c
Compiling frame/1/addv/bli_addv.c
Compiling frame/1/addv/bli_addv_check.c
Compiling frame/1/addv/bli_addv_kernel.c
Compiling frame/1/addv/bli_addv_ref.c
Compiling frame/1/axpyv/bli_axpyv.c
Compiling frame/1/axpyv/bli_axpyv_check.c
Compiling frame/1/axpyv/bli_axpyv_kernel.c
Compiling frame/1/axpyv/bli_axpyv_ref.c
Compiling frame/1/copyv/bli_copyv.c
Compiling frame/1/copyv/bli_copyv_check.c
Compiling frame/1/copyv/bli_copyv_kernel.c
Compiling frame/1/copyv/bli_copyv_ref.c
Compiling frame/1/dotv/bli_dotv.c
Compiling frame/1/dotv/bli_dotv_check.c
Compiling frame/1/dotv/bli_dotv_kernel.c
Compiling frame/1/dotv/bli_dotv_ref.c
Compiling frame/1/dotxv/bli_dotxv.c
Compiling frame/1/dotxv/bli_dotxv_check.c
Compiling frame/1/dotxv/bli_dotxv_kernel.c
Compiling frame/1/dotxv/bli_dotxv_ref.c
Compiling frame/1/invertv/bli_invertv.c
Compiling frame/1/invertv/bli_invertv_check.c
Compiling frame/1/invertv/bli_invertv_kernel.c
Compiling frame/1/invertv/bli_invertv_ref.c
Compiling frame/1/packv/bli_packv.c
Compiling frame/1/packv/bli_packv_check.c
Compiling frame/1/packv/bli_packv_cntl.c
Compiling frame/1/packv/bli_packv_init.c
"config/bgq/kernels/1/bli_axpyv_opt_var1.c", line 45.33: 1506-1418 (E) Assignment between restrict pointers "alpha" and "alpha_in" is not allowed. Only outer-to-inner scope assignments between restrict pointers are allowed.
"config/bgq/kernels/1/bli_axpyv_opt_var1.c", line 46.29: 1506-1418 (E) Assignment between restrict pointers "x" and "x_in" is not allowed. Only outer-to-inner scope assignments between restrict pointers are allowed.
"config/bgq/kernels/1/bli_axpyv_opt_var1.c", line 47.29: 1506-1418 (E) Assignment between restrict pointers "y" and "y_in" is not allowed. Only outer-to-inner scope assignments between restrict pointers are allowed.
"config/bgq/kernels/1/bli_axpyv_opt_var1.c", line 68.28: 1506-754 (S) The parameter type is not valid for a function of this linkage type.
make: *** [obj/bgq/config/kernels/1/bli_axpyv_opt_var1.o] Error 1
make: *** Waiting for unfinished jobs....
—
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from blis.

As Tyler pointed out, BLIS is not yet completely restrict-compliant. This is partially my fault for misusing the keyword to begin with, and partially gcc's fault for not informing me of the misuse with a warning. :)

I am trying to fix these as I find them, but it's kind of like whack-a-mole. Especially since none of my primary development machines have xlc.

from blis.

I will add the curly braces rather than give up the benefits of anti-aliasing.

Field: you can get an an ALCF account from me any time.

from blis.

This particular instances (config/bgq/kernels/1/bli_axpyv_opt_var1.c) can easily be fixed even without curlies. I will push a new commit soon.

Thanks for the offer, Jeff. I will take you up on it sometime!

from blis.

Jeff: please confirm that this has been fixed. If not, I suspect it is because there are other instances of the same problem that the build process now gets to that it was not getting to previously. If so, let's just keep the issue/thread going till we stomp them all out.

from blis.

With the latest commit, I saw this:

"config/bgq/kernels/1/bli_axpyv_opt_var1.c", line 64.28: 1506-754 (S) The parameter type is not valid for a function of this linkage type.
make: *** [obj/bgq/config/kernels/1/bli_axpyv_opt_var1.o] Error 1
make: *** Waiting for unfinished jobs....

I fixed like this:

[jhammond@vestalac1 blis]$ git diff
diff --git a/kernels/bgq/1/bli_axpyv_opt_var1.c b/kernels/bgq/1/bli_axpyv_opt_var1.c
index 495ab60..163e8bb 100644
--- a/kernels/bgq/1/bli_axpyv_opt_var1.c
+++ b/kernels/bgq/1/bli_axpyv_opt_var1.c
@@ -61,7 +61,7 @@ void bli_daxpyv_opt_var1(
     dim_t n_left      = n % 4;

     vector4double xv, yv, zv;
-    vector4double alphav = vec_lds( 0 * sizeof(double), alpha );
+    vector4double alphav = vec_lds( 0 * sizeof(double), (double*)alpha );

     #pragma omp parallel for
        for ( dim_t i = 0; i < n_run; i++ )

Don't ask me why vec_lds won't take a restrict pointer. http://pic.dhe.ibm.com/infocenter/compbg/v121v141/index.jsp?topic=%2Fcom.ibm.xlcpp121.bg.doc%2Fcompiler_ref%2Fvec_lds.html does not mention this semantic restriction.

from blis.

Thanks again, Jeff.

from blis.