Plumed error with PESMD

[Gourav Chakraborty]

Hello Everyone, 

I am trying to perform a test PESMD run with plumed, this was my input script:

temperature 0.722
tstep 0.005
friction 1
dimension 2
nstep 50
ipos 0.0 0.0

and this was my plumed.dat file:
d1: DISTANCE ATOMS=1,2 COMPONENTS
ff: MATHEVAL ARG=d1.x,d1,y PERIODIC=NO FUNC=()
bb: BIASVALUE ARG=ff

but I got this error:
plumed pesmd < input

terminate called after throwing an instance of 'PLMD::Plumed::ExceptionError'

  what():  

(core/CLTool.cpp:54) void PLMD::CLTool::parseFlag(const string&, bool&)

+++ assertion failed: inputData.count(key)>0

[kalam:48019] *** Process received signal ***

[kalam:48019] Signal: Aborted (6)

[kalam:48019] Signal code:  (-6)

[kalam:48019] [ 0] /lib/x86_64-linux-gnu/libc.so.6(+0x43090)[0x14b817253090]

[kalam:48019] [ 1] /lib/x86_64-linux-gnu/libc.so.6(gsignal+0xcb)[0x14b81725300b]

[kalam:48019] [ 2] /lib/x86_64-linux-gnu/libc.so.6(abort+0x12b)[0x14b817232859]

[kalam:48019] [ 3] /lib/x86_64-linux-gnu/libstdc++.so.6(+0xa4ee6)[0x14b8174cdee6]

[kalam:48019] [ 4] /lib/x86_64-linux-gnu/libstdc++.so.6(+0xb6f8c)[0x14b8174dff8c]

[kalam:48019] [ 5] /lib/x86_64-linux-gnu/libstdc++.so.6(+0xb6ff7)[0x14b8174dfff7]

[kalam:48019] [ 6] /lib/x86_64-linux-gnu/libstdc++.so.6(__cxa_rethrow+0x4b)[0x14b8174e02ab]

[kalam:48019] [ 7] plumed(+0x6e3c)[0x556e339b6e3c]

[kalam:48019] [ 8] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0x14b817234083]

[kalam:48019] [ 9] plumed(+0x708e)[0x556e339b708e]

[kalam:48019] *** End of error message ***

Aborted (core dumped)

I simply followed the standard protocol highlighted in plumed's page. Any help will be highly appreciated.