[cleanup] Remove some unused variables

Found by GCC 16 (-Wunused-variable).

Author: gruenich

experimental/algorithm/LAGr_MaxFlow.c

@@ -698,7 +698,9 @@ int LAGr_MaxFlow
   GrB_Vector invariant = NULL ;
   GrB_BinaryOp CheckInvariant = NULL ;
   GrB_Scalar check = NULL ;
+  #ifdef DBG
   bool check_raw;
+  #endif
 
   // descriptor for matrix building
   GrB_Descriptor desc = NULL ;

experimental/benchmark/FastAssign_demo.c

@@ -50,10 +50,7 @@ int main (int argc, char **argv)
     GrB_Index *rand_a = NULL;
     GrB_Scalar bool1 = NULL;
     bool *set_a = NULL;
-    GrB_Index r_size = 0, ramp_size = 0, junk_size = 0;
-    bool iso = false;
 
-    bool *val_of_P = NULL;
     double t = LAGraph_WallClockTime ( ) ;
     GrB_Index size = (argc > 1) ? atoll(argv [1]) : 1000 ;
     int shift_e = 63 - (int) floor (log2 ((double) size)) ;

experimental/benchmark/Incidence_Matrix_demo.c

@@ -58,7 +58,6 @@ int main (int argc, char **argv)
     // mtx2bin_demo).
 
     double t = LAGraph_WallClockTime ( ) ;
-    char *matrix_name = (argc > 1) ? argv [1] : "stdin" ;
     LG_TRY (readproblem (
         &G,         // the graph that is read from stdin or a file
         NULL,       // source nodes (none, if NULL)

experimental/benchmark/SwapEdges_demo.c

@@ -57,7 +57,6 @@ int main (int argc, char **argv)
 
     double t = LAGraph_WallClockTime ( ) ;
     GrB_Index swaps = (argc > 2) ? atoi(argv [2]): 100;
-    char *matrix_name = (argc > 1) ? argv [1] : "stdin" ;
     FILE *f = (argc > 3) ? fopen (argv[3], "w"): NULL;
     LG_TRY (readproblem (
         &G,         // the graph that is read from stdin or a file

experimental/benchmark/apply_demo.c

@@ -21,7 +21,6 @@ int main(int argc, char **argv)
 {
     char msg [LAGRAPH_MSG_LEN] ;
 
-    LAGraph_Graph G = NULL ;
     GrB_Matrix A = NULL ;
     GrB_Matrix Res = NULL ;
     GrB_Scalar s = NULL ;

experimental/benchmark/build_demo.c

@@ -69,7 +69,6 @@ int main (int argc, char **argv)
     // mtx2bin_demo).
 
     double t = LAGraph_WallClockTime ( ) ;
-    char *matrix_name = (argc > 1) ? argv [1] : "stdin" ;
     LG_TRY (readproblem (
         &G,         // the graph that is read from stdin or a file
         NULL,       // source nodes (none, if NULL)

experimental/benchmark/coarsen_matching_demo.c

@@ -150,7 +150,6 @@ int main(int argc, char **argv)
 
         for (int trial = 0 ; trial < ntrials ; trial++)
         {
-            int64_t seed = trial * n + 1 ;
             double tt = LAGraph_WallClockTime ( ) ;
 
             LG_TRY (LAGraph_Coarsen_Matching (&coarsened, &parent_result, &newlabel_result, &inv_newlabel_result, G, LAGraph_Matching_heavy, 0, 1, DEFAULT_SEED, msg)) ;

experimental/benchmark/coloring_IS_demo.c

@@ -36,7 +36,6 @@ int main (int argc, char **argv)
     //--------------------------------------------------------------------------
 
     double t = LAGraph_WallClockTime ( ) ;
-    char *matrix_name = (argc > 1) ? argv [1] : "stdin" ;
     LG_TRY (readproblem (
         &G,         // the graph that is read from stdin or a file
         NULL,       // source nodes (none, if NULL)
@@ -58,14 +57,14 @@ int main (int argc, char **argv)
 
     t = LAGraph_WallClockTime ( ) ;
     int status = (LAGraph_coloring_independent_set (&C, &num_colors, G, msg)) ;
+    (void) status;
     alg_time = LAGraph_WallClockTime ( ) - t ;
     printf ("Time for IS Coloring:        %g sec\n", alg_time) ;
 
     //--------------------------------------------------------------------------
     // check the results
     //--------------------------------------------------------------------------
 
-    bool isequal ;
     t = LAGraph_WallClockTime ( ) ;
     LAGRAPH_TRY (LG_check_coloring(G, C, msg)) ;
     t = LAGraph_WallClockTime ( ) - t ;

experimental/benchmark/coloring_MIS_demo.c

@@ -36,7 +36,6 @@ int main (int argc, char **argv)
     //--------------------------------------------------------------------------
 
     double t = LAGraph_WallClockTime ( ) ;
-    char *matrix_name = (argc > 1) ? argv [1] : "stdin" ;
     LG_TRY (readproblem (
         &G,         // the graph that is read from stdin or a file
         NULL,       // source nodes (none, if NULL)
@@ -58,14 +57,14 @@ int main (int argc, char **argv)
 
     t = LAGraph_WallClockTime ( ) ;
     int status = (LAGraph_coloring_MIS (&C, &num_colors, G, msg)) ;
+    (void) status;
     alg_time = LAGraph_WallClockTime ( ) - t ;
     printf ("Time for MIS Coloring:        %g sec\n", alg_time) ;
 
     //--------------------------------------------------------------------------
     // check the results
     //--------------------------------------------------------------------------
 
-    bool isequal ;
     t = LAGraph_WallClockTime ( ) ;
     LAGRAPH_TRY (LG_check_coloring(G, C, msg)) ;
     t = LAGraph_WallClockTime ( ) - t ;

experimental/benchmark/colscale_demo.c

@@ -18,7 +18,6 @@ int main(int argc, char **argv)
 {
     char msg [LAGRAPH_MSG_LEN] ;
 
-    LAGraph_Graph G = NULL ;
     GrB_Matrix D = NULL ;
     GrB_Matrix A = NULL ;
     GrB_Matrix Res = NULL ;