Create the CombBLAS::SpParMat with the MPI_Comm from the input 'gridinfo_t'.
This prevents a warning/error from CombBLAS about using MPI_COMM_WORLD.

--- a/SRC/dHWPM_CombBLAS.hpp
+++ b/SRC/dHWPM_CombBLAS.hpp
@@ -52,7 +52,7 @@
     {
         printf("AWPM only supports square process grid. Retuning without a permutation.\n");
     }
-    combblas::SpParMat < int_t, double, combblas::SpDCCols<int_t,double> > Adcsc;
+    combblas::SpParMat < int_t, double, combblas::SpDCCols<int_t,double> > Adcsc(grid->comm);
     std::vector< std::vector < std::tuple<int_t,int_t,double> > > data(procs);
     
     /* ------------------------------------------------------------
--- a/SRC/zHWPM_CombBLAS.hpp
+++ b/SRC/zHWPM_CombBLAS.hpp
@@ -52,7 +52,7 @@
     {
         printf("AWPM only supports square process grid. Retuning without a permutation.\n");
     }
-    combblas::SpParMat < int_t, double, combblas::SpDCCols<int_t,double> > Adcsc;
+    combblas::SpParMat < int_t, double, combblas::SpDCCols<int_t,double> > Adcsc(grid->comm);
     std::vector< std::vector < std::tuple<int_t,int_t,double> > > data(procs);
     
     /* ------------------------------------------------------------
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<tr><td><span title='2023-11-05 23:23:23 +0100'>2023-11-05</span></td><td><a href='/guix/commit/gnu/tests.scm?id=0c695bbf8dbd5a5c1224f331a78b6316bc16e4d1'>tests: Honor system and target when lowering &lt;system-test&gt;.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>