[ITensors] [ENCHANCEMENT] Remove TimerOutputs.jl as a dependency

[MazenAli]

Description of bug

The @timeit_debug decorator from TimerOutputs does not to seem to function properly as timeit_debug_enabled is not defined in ITensors. See also screenshot of README from TimerOutputs.

Minimal runnable code

using Pkg
Pkg.add("TimerOutputs")

using ITensors, ITensorMPS, TimerOutputs
TimerOutputs.enable_debug_timings(ITensors)
const timer = TimerOutput()

# Build MPO
J = 4.0
h = 1.0
L = 15
ampo = AutoMPO()
for j in 1:(L - 1)
  add!(ampo, -J, "Sz", j, "Sz", j + 1)
  add!(ampo, -h, "Sx", j)
end
add!(ampo, -h, "Sx", L)
sites = siteinds("S=1/2", L)
ham = MPO(ampo, sites)

# Do DMRG
psi0 = MPS(sites, "Up")
nsweeps = 20
maxdim = 15
cutoff = 0

@timeit_debug timer "dmrg" energy, _ = dmrg(ham, psi0;
                 nsweeps=nsweeps,
                 maxdim=maxdim,
                 mindim=maxdim,
                 cutoff=cutoff,
                 outputlevel=0)
println("Run $i: $energy")
println(timer)

Output of minimal runnable code

root@8506b93efb68:/opt/project/examples# julia tmp.jl 
   Resolving package versions...
  No Changes to `~/.julia/environments/v1.10/Project.toml`
  No Changes to `~/.julia/environments/v1.10/Manifest.toml`
ERROR: LoadError: UndefVarError: `timeit_debug_enabled` not defined
Stacktrace:
 [1] enable_debug_timings(m::Module)
   @ TimerOutputs ~/.julia/packages/TimerOutputs/Lw5SP/src/TimerOutput.jl:187
 [2] top-level scope
   @ /opt/project/examples/tmp.jl:5
in expression starting at /opt/project/examples/tmp.jl:5
root@8506b93efb68:/opt/project/examples# 

Version information

• Output from versioninfo():

julia> versioninfo()
Julia Version 1.10.5
Commit 6f3fdf7b362 (2024-08-27 14:19 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (aarch64-linux-gnu)
  CPU: 8 × unknown
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, generic)
Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)
Environment:
  JULIA_GPG = 3673DF529D9049477F76B37566E3C7DC03D6E495
  JULIA_VERSION = 1.10.5
  JULIA_PATH = /usr/local/julia

• Output from using Pkg; Pkg.status("ITensors"):

julia> using Pkg; Pkg.status("ITensors")
Status `~/.julia/environments/v1.10/Project.toml`
  [9136182c] ITensors v0.6.17

[mtfishman]

I don't think we have many timers inside the codebase right now anyway, what were you hoping to time?

As an alternative, I would recommend using a profiler.

[MazenAli]

I wanted to time dmrg, i.e., how much time dmrg spends in the subroutines, e.g., truncating, eigenvalue solve, etc. You do use the timeit_debug decorators, but I couldn't find tests for it. Did you test it?

[mtfishman]

I don't remember testing it, I haven't used TimerOutputs in a long time, we were mostly using it in the codebase for debugging some performance issues early on when developing the package. Probably we should remove it at this point, it isn't really meant for external users.

[mtfishman]

I'll keep this issue open as a reminder to remove TimerOutputs from the codebase.

@MazenAli to summarize, I would recommend using a profiler instead, or dev'ing the package and adding your own timers with TimerOutputs if you prefer to use TimerOutputs.