[patch,libgfortran] PR51119 - MATMUL slow for large matrices

[Jerry DeLisle]

On 11/13/2016 11:03 PM, Thomas Koenig wrote:
> Hi Jerry,
>
> I think this
>
> +      /* Parameter adjustments */
> +      c_dim1 = m;
> +      c_offset = 1 + c_dim1;
>
> should be
>
> +      /* Parameter adjustments */
> +      c_dim1 = rystride;
> +      c_offset = 1 + c_dim1;
>
> Regarding options for matmul:  It is possible to add the
> options to the lines in Makefile.in
>
> # Turn on vectorization and loop unrolling for matmul.
> $(patsubst %.c,%.lo,$(notdir $(i_matmul_c))): AM_CFLAGS += -ftree-vectorize
> -funroll-loops
>
> This is a great step forward.  I think we can close most matmul-related
> PRs once this patch has been applied.
>
> Regards
>
>     Thomas
>

With Thomas suggestion, I can remove the #pragma optimize from the source code. 
Doing this: (long lines wrapped as shown)

diff --git a/libgfortran/Makefile.am b/libgfortran/Makefile.am
index 39d3e11..9ee17f9 100644
--- a/libgfortran/Makefile.am
+++ b/libgfortran/Makefile.am
@@ -850,7 +850,7 @@ intrinsics/dprod_r8.f90 \
  intrinsics/f2c_specifics.F90

  # Turn on vectorization and loop unrolling for matmul.
-$(patsubst %.c,%.lo,$(notdir $(i_matmul_c))): AM_CFLAGS += -ftree-vectorize 
-funroll-loops
+$(patsubst %.c,%.lo,$(notdir $(i_matmul_c))): AM_CFLAGS += -ffast-math 
-fno-protect-parens -fstack-arrays -ftree-vectorize -funroll-loops --param 
max-unroll-times=4 -ftree-loop-vectorize
  # Logical matmul doesn't vectorize.
  $(patsubst %.c,%.lo,$(notdir $(i_matmull_c))): AM_CFLAGS += -funroll-loops


Comparing gfortran 6 vs 7: (test program posted in PR51119)

$ gfc6 -static -Ofast -finline-matmul-limit=32 -funroll-loops --param 
max-unroll-times=4 compare.f90
$ ./a.out
  =========================================================
  ================            MEASURED GIGAFLOPS          =
  =========================================================
                  Matmul                           Matmul
                  fixed                 Matmul     variable
  Size  Loops     explicit   refMatmul  assumed    explicit
  =========================================================
     2  2000     11.928      0.047      0.082      0.138
     4  2000      1.455      0.220      0.371      0.316
     8  2000      1.476      0.737      0.704      1.574
    16  2000      4.536      3.755      2.825      3.820
    32  2000      6.070      5.443      3.124      5.158
    64  2000      5.423      5.355      5.405      5.413
   128  2000      5.913      5.841      5.917      5.917
   256   477      5.865      5.252      5.863      5.862
   512    59      2.794      2.841      2.794      2.791
  1024     7      1.662      1.356      1.662      1.661
  2048     1      1.753      1.724      1.753      1.754

$ gfc -static -Ofast -finline-matmul-limit=32 -funroll-loops --param 
max-unroll-times=4 compare.f90
$ ./a.out
  =========================================================
  ================            MEASURED GIGAFLOPS          =
  =========================================================
                  Matmul                           Matmul
                  fixed                 Matmul     variable
  Size  Loops     explicit   refMatmul  assumed    explicit
  =========================================================
     2  2000     12.146      0.042      0.090      0.146
     4  2000      1.496      0.232      0.384      0.325
     8  2000      2.330      0.765      0.763      0.965
    16  2000      4.611      4.120      2.792      3.830
    32  2000      6.068      5.265      3.102      4.859
    64  2000      6.527      5.329      6.425      6.495
   128  2000      8.207      5.643      8.336      8.441
   256   477      9.210      4.967      9.367      9.299
   512    59      8.330      2.772      8.422      8.342
  1024     7      8.430      1.378      8.511      8.424
  2048     1      8.339      1.718      8.425      8.322

I do think we need to adjust the default inline limit and should do this 
separately from this patch.

With these changes, OK for trunk?

Regards,

Jerry