Re: Installation with tcl

From: Josh Vermaas (
Date: Wed Dec 16 2020 - 16:50:53 CST

1. My preferred way of doing this is to just grab a precompiled version of
tcl from the UIUC website. Ex.

You'd then untar the directory and name it either tcl or tcl-threaded.
2. The reason I do this is because for 99.999% of users, the version of tcl
you use has no impact whatsoever. Tcl is used to make the input decks able
to do more things, but the performance is limited by the underlying C/C++
implementations of the MD engine. The possible exception to this is if you
are using tclforces, where the tcl is part of the iteration. However, I
doubt that 8.6 vs 8.5 will make any difference in performance even in that

That all being said, it *should* be possible to system tcl libraries too. I
think where you got caught is by the old build system. The main configure
script assembles the makefile within the build directory from the files in
the arch directory. Without deleting the directory and reconfiguring, I
have seen instances where changes to the arch files do not propagate to the


On Wed, Dec 16, 2020 at 3:23 PM Arturo Fernandez <>

> Hello,
> My system has tcl pre-installed with the headers at /usr/include/tcl8.6.
> The NAMD (2.14) installation is producing the error:
> ...
> g++ -m64 -std=c++0x
> -I/home/ubuntu/charm-v6.10.2/mpi-linux-x86_64-gfortran-mpicxx/include
> -DCMK_OPTIMIZE=1 -Isrc -Iinc -Iplugins/include -Icolvars/src
> -DSTATIC_PLUGIN -I/usr/include/tcl8.6/include -DNAMD_TCL
> -I/Projects/namd2/fftw/linux-x86_64/include -DNAMD_FFTW
> -DNAMD_VERSION=\"2.14\" -DNAMD_PLATFORM=\"Linux-x86_64-MPI\"
> -fexpensive-optimizations -ffast-math -o obj/eabfTcl.o -c src/eabfTcl.C
> src/eabfTcl.C:22:10: fatal error: tcl.h: No such file or directory
> #include <tcl.h>
> ^~~~~~~
> compilation terminated.
> Make.depends:360: recipe for target 'obj/eabfTcl.o' failed
> make: *** [obj/eabfTcl.o] Error 1
> After seeing it somewhere, I tried export TCLINCL=-I/usr/include/tcl8.6
> but didn't make any difference. I have 2 questions:
> 1) Which would be the recommended installation procedure when tcl is
> pre-installed?
> 2) Does tcl have any impact on performance?
> Thanks.

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