add a simple makefile

Makefile

@@ -0,0 +1,29 @@
+
+# the most basic way of building that is most likely to work on most systems
+.PHONY: run
+run: run.c
+	gcc -O3 -o run run.c -lm
+
+# https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
+# https://simonbyrne.github.io/notes/fastmath/
+# -Ofast enables all -O3 optimizations. 
+# Disregards strict standards compliance.
+# It also enables optimizations that are not valid for all standard-compliant programs. 
+# It turns on -ffast-math, -fallow-store-data-races and the Fortran-specific 
+# -fstack-arrays, unless -fmax-stack-var-size is specified, and -fno-protect-parens. 
+# It turns off -fsemantic-interposition.
+# In our specific application this is *probably* okay to use
+.PHONY: runfast
+runfast: run.c
+	gcc -Ofast -o run run.c -lm
+
+# additionally compiles with OpenMP, allowing multithreaded runs
+# make sure to also enable multiple threads when running, e.g.:
+# OMP_NUM_THREADS=4 ./run out/model.bin
+.PHONY: runomp
+runomp: run.c
+	gcc -Ofast -fopenmp -march=native run.c  -lm  -o run
+
+.PHONY: clean
+clean:
+	rm -f run