make_graph.c:43:10: fatal error: 'omp.h' file not found

[VFVrPQ]

make all but has the following error:

gcc -g -std=c99 -Wall -Drestrict=__restrict__ -O3 -DNDEBUG -ffast-math  -DGRAPH_GENERATOR_SEQ -g -o generator_seq generator_seq.c graph_generator.c make_graph.c splittable_mrg.c utils.c -lm
generator_seq.c:115:35: warning: format specifies type 'unsigned long' but the argument has type 'int64_t' (aka 'long long') [-Wformat]
      fprintf(fout, "%lu\t%lu\n", get_v0_from_edge(result + i), get_v1_from_edge(result + i));
                     ~~~          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
                     %lld
generator_seq.c:115:65: warning: format specifies type 'unsigned long' but the argument has type 'int64_t' (aka 'long long') [-Wformat]
      fprintf(fout, "%lu\t%lu\n", get_v0_from_edge(result + i), get_v1_from_edge(result + i));
                          ~~~                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
                          %lld
2 warnings generated.
make_graph.c:43:10: fatal error: 'omp.h' file not found
#include <omp.h>
         ^~~~~~~
1 error generated.
make: *** [generator_seq] Error 1

How to solve it.

[shixuansun]

Please setup the OpenMP environment before compiling the code.