Regtest

I checked that this regtest fails without last commit

Related to #190

regtest/basic/rt-mpi6c/Makefile

+include ../../scripts/test.make

regtest/basic/rt-mpi6c/config

+mpiprocs=3
+type=driver
+# this is to test a different name
+arg="--plumed=plumed.dat --timestep=0.05 --ixyz trajectory.xyz --multi 3"

regtest/basic/rt-mpi6c/plumed.0.dat

+_SET_SUFFIX .a
+c: DISTANCE ATOMS=1,2
+d: DISTANCE ATOMS=2,3
+
+# this is a dummy file, just to enable checking
+PRINT FILE=colvar ARG=c
+
+# the HILLS file are not really checked here since non-mpi walkers are not reproducible
+# however, this example crashes
+single: METAD ARG=c,d SIGMA=0.1,0.2 HEIGHT=0.1 PACE=2  WALKERS_ID=0 WALKERS_DIR=. WALKERS_N=3 WALKERS_RSTRIDE=1
+

regtest/basic/rt-mpi6c/plumed.1.dat

+_SET_SUFFIX .a
+c: DISTANCE ATOMS=1,2
+d: DISTANCE ATOMS=2,3
+
+single: METAD ARG=c,d SIGMA=0.1,0.2 HEIGHT=0.1 PACE=2  WALKERS_ID=1 WALKERS_DIR=. WALKERS_N=3 WALKERS_RSTRIDE=1
+

regtest/basic/rt-mpi6c/plumed.2.dat

+_SET_SUFFIX .a
+c: DISTANCE ATOMS=1,2
+d: DISTANCE ATOMS=2,3
+
+single: METAD ARG=c,d SIGMA=0.1,0.2 HEIGHT=0.1 PACE=2 WALKERS_ID=2 WALKERS_DIR=. WALKERS_N=3 WALKERS_RSTRIDE=1
+