Maybe I shouldn't have formed the ASSUME directive that way, but an ICE is always a bug. See attached
ifort -V
Intel(R) Fortran Intel(R) 64 Compiler for applications running on Intel(R) 64, Version 16.0.1.150 Build 20151021
Copyright (C) 1985-2015 Intel Corporation. All rights reserved.
pfe27.dkokron 159> ifort -O2 -extend-source -c BlockTriDiagSolver.f
04010002_15114
BlockTriDiagSolver.f(10): catastrophic error: **Internal compiler error: internal abort** Please report this error along with the circumstances in which it occurred in a Software Problem Report. Note: File and line given may not be explicit cause of this error.
compilation aborted for BlockTriDiagSolver.f (code 1)