Add a "nompi" target to the Makefile

Makefile

@@ -33,10 +33,13 @@ NVCC=nvcc $(NVCCOPTS)
 CXXFILES = dlrho.cc gen_N.cc
 CUFILES = parrhoasm.cu dpstream.cu
 OFILES = dlrho.o gen_N.o cudadl.o controller.o controller_main.o evutils.o dpnode.o dpnode_main.o worker.o worker_main.o
-TARGETS = gen_N dlrho controller dpnode worker mpi
+NOMPI_TARGETS = gen_N dlrho controller dpnode worker
+TARGETS = $(NOMPI_TARGETS) mpi
 
 all: $(TARGETS)
 
+nompi: $(NOMPI_TARGETS)
+
 gen_N: gen_N.o
 	g++ -g -Wall $^ -o $@ -lntl -L$(GMP)/lib -lgmp