diff --git a/regtest/basic/rt71c/Makefile b/regtest/basic/rt71c/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..3703b27cea227aa053fb6d1d73f861e4384dbcee
--- /dev/null
+++ b/regtest/basic/rt71c/Makefile
@@ -0,0 +1 @@
+include ../../scripts/test.make
diff --git a/regtest/basic/rt71c/centers.reference b/regtest/basic/rt71c/centers.reference
new file mode 100644
index 0000000000000000000000000000000000000000..332c5b426711f28da7271f5f3ef720e5184dfcaa
--- /dev/null
+++ b/regtest/basic/rt71c/centers.reference
@@ -0,0 +1,50 @@
+8
+ 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000
+X 0.000000 0.000000 0.000000
+X 1.000000 0.000000 0.000000
+X 0.000000 0.000000 -1.000000
+X 0.333333 0.000000 -0.333333
+X 0.333333 0.000000 -0.333333
+X 0.333333 0.000000 -0.333333
+X 0.333333 0.000000 0.000000
+X 0.333333 0.000000 0.000000
+8
+ 4.000000 4.000000 4.000000
+X 10.000000 10.000000 10.000000
+X 11.000000 10.000000 10.000000
+X 10.000000 10.000000 9.000000
+X 10.333333 10.000000 9.666667
+X 10.333333 10.000000 9.666667
+X -1.704833 2.000000 1.704833
+X -1.704833 2.000000 2.000000
+X -1.704833 2.000000 2.000000
+8
+ 100.000000 1.000000 1.000000 1.000000 100.000000 1.000000 1.000000 1.000000 100.000000
+X 1.000000 2.000000 3.000000
+X 4.000000 7.000000 2.000000
+X 1.000000 9.000000 13.000000
+X 2.000000 6.000000 6.000000
+X 2.000000 6.000000 6.000000
+X 1.998141 6.007338 5.943370
+X 1.998671 3.660581 2.666655
+X 1.998671 3.660581 2.666655
+8
+ 100.000000 9.000000 8.000000 7.000000 40.000000 3.000000 2.000000 1.000000 30.000000
+X 1.000000 2.000000 3.000000
+X 4.000000 7.000000 2.000000
+X 1.000000 9.000000 13.000000
+X 2.000000 6.000000 6.000000
+X 2.000000 6.000000 6.000000
+X 1.945398 6.017210 5.062714
+X 1.993191 3.630205 2.665897
+X 1.993191 3.630205 2.665897
+8
+ 1.000000 1.000000 1.000000
+X 0.100000 0.100000 -99.900000
+X 0.200000 0.200000 23.200000
+X 0.300000 1.300000 33.300000
+X 0.200000 0.533333 -14.466667
+X 0.200000 0.200000 -99.800000
+X 0.200000 0.200000 0.200000
+X 0.132829 0.132829 0.132829
+X 0.132829 0.132829 0.132829
diff --git a/regtest/basic/rt71c/config b/regtest/basic/rt71c/config
new file mode 100644
index 0000000000000000000000000000000000000000..95dbc60aa440902df95fc053907535bd854d7c41
--- /dev/null
+++ b/regtest/basic/rt71c/config
@@ -0,0 +1,2 @@
+type=driver
+arg="--plumed plumed.dat --ixyz trajectory.xyz --dump-forces ff --dump-forces-fmt=%10.6f --dump-full-virial --debug-forces debugforces"
diff --git a/regtest/basic/rt71c/ff.reference b/regtest/basic/rt71c/ff.reference
new file mode 100644
index 0000000000000000000000000000000000000000..3f4d83f735bd9978e1894cf6be783b38054efe25
--- /dev/null
+++ b/regtest/basic/rt71c/ff.reference
@@ -0,0 +1,25 @@
+3
+  0.235702   0.000000  -0.235702   0.000000   0.000000   0.000000  -0.235702   0.000000   0.235702
+X   0.471405   0.000000  -0.471405
+X  -0.235702   0.000000   0.235702
+X  -0.235702   0.000000   0.235702
+3
+  0.208715   0.000000  -0.208715   0.000000   0.000000   0.000000  -0.208715   0.000000   0.208715
+X   0.424264   0.000000  -0.424264
+X  -0.141421   0.000000   0.282843
+X  -0.282843   0.000000   0.141421
+3
+  0.196454   0.788725   0.579314   0.788725   3.166572   2.325831   0.579314   2.325831   1.708312
+X   0.131057   0.530627   0.380547
+X  -0.065339  -0.267311  -0.196897
+X  -0.065718  -0.263316  -0.183650
+3
+  0.193721   0.823164   0.422670   0.823164   3.497813   1.796020   0.422670   1.796020   0.922201
+X   0.120758   0.607062   0.254492
+X  -0.083411  -0.320661  -0.159031
+X  -0.083505  -0.290919   0.016328
+3
+  0.057735   0.057735   0.057735   0.057735   0.057735   0.057735   0.057735   0.057735   0.057735
+X   0.398939   0.398939   0.398939
+X  -0.220528  -0.220528  -0.220528
+X  -0.178411  -0.178411  -0.178411
diff --git a/regtest/basic/rt71c/plumed.dat b/regtest/basic/rt71c/plumed.dat
new file mode 100644
index 0000000000000000000000000000000000000000..02a01f87cca237c50a27aeb4055fb52fbe8379ed
--- /dev/null
+++ b/regtest/basic/rt71c/plumed.dat
@@ -0,0 +1,21 @@
+# dummy stuff using during optimization of the code:
+# DEBUG DETAILED_TIMERS
+# gg: GROUP ATOMS=1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3
+# g: GROUP ATOMS=gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg,gg
+
+## NOTE
+## I used this with --debug-forces to debug forces on CENTER PHASES
+## since phases are disabled when PBC matrix is null
+## they clearly cannot agree with numerical difference in that case.
+## GB
+g: GROUP ATOMS=1,2,3
+ce1: CENTER ATOMS=g NOPBC
+ce2: CENTER ATOMS=g 
+ce3: CENTER ATOMS=g PHASES
+ce4: CENTER ATOMS=1,2,3 PHASES WEIGHTS=2,1,0
+ce5: CENTER ATOMS=1,1,2 PHASES
+DUMPATOMS ATOMS=1,2,3,ce1,ce2,ce3,ce4,ce5 FILE=centers
+de:  DISTANCE ATOMS=1,ce3
+dev: BIASVALUE ARG=de
+
+
diff --git a/regtest/basic/rt71c/trajectory.xyz b/regtest/basic/rt71c/trajectory.xyz
new file mode 100644
index 0000000000000000000000000000000000000000..f13e660cba0d59f0f9a11e26ededbe65afba3177
--- /dev/null
+++ b/regtest/basic/rt71c/trajectory.xyz
@@ -0,0 +1,25 @@
+3
+0 0 0 
+X 0 0 0
+X 1 0 0
+X 0 0 -1
+3
+4 4 4
+X 10 10 10
+X 11 10 10
+X 10 10 9
+3
+100 1 1 1 100 1 1 1 100
+X 1 2 3
+X 4 7 2
+X 1 9 13
+3
+100 9 8 7 40 3 2 1 30
+X 1 2 3
+X 4 7 2
+X 1 9 13
+3
+1 0 0 0 1 0 0 0 1
+X 0.1 0.1 -99.9
+X 0.2 0.2 23.2
+X 0.3 1.3 33.3