Edited Ques: @printf not printing anythin in following

_SACHIN · April 7, 2022, 5:47am

Why @printf at the end is not printing anything for the following ?
Note iTensors is a package. So you might ignore the code.

using ITensors
using Printf
function ITensors.op(::OpName"expτSS", ::SiteType"S=1/2", s1::Index, s2::Index; τ)
h =
1 / 2 * op(“S+”, s1) * op(“S-”, s2) +
1 / 2 * op(“S-”, s1) * op(“S+”, s2) +
op(“Sz”, s1) * op(“Sz”, s2)
return exp(τ * h)
end
function main(; N=10, cutoff=1E-8, δτ=0.1, beta_max=2.0)
s = siteinds(“S=1/2”, N; conserve_qns=true)
gates = ops([(“expτSS”, (n, n + 1), (τ=-δτ / 2,)) for n in 1:(N - 1)], s)
append!(gates, reverse(gates))
rho = MPO(s, “Id”) ./ √2
terms = OpSum()
for j in 1:(N - 1)
terms += 1 / 2, “S+”, j, “S-”, j + 1
terms += 1 / 2, “S-”, j, “S+”, j + 1
terms += “Sz”, j, “Sz”, j + 1
end
H = MPO(terms, s)
for β in 0:δτ:beta_max
energy = inner(rho, H)
@printf(“β = %.2f energy = %.8f\n”, β, energy)
rho = apply(gates, rho; cutoff)
rho = rho / tr(rho)
end
return nothing
end

yashi · April 7, 2022, 5:59am

Hi @_SACHIN

Welcome to Julia

It’s always good idea to

post a minimal working example
put your code in code block
post errors you get by running the mwe
post your expectations

The following code worked on my Julia 1.7

using Printf
δτ=1
beta_max=10
energy = 1.0
for β in 0:δτ:beta_max
    @printf("β = %.2f energy = %.8f\n", β, energy)
end

output:

β = 0.00 energy = 1.00000000
β = 1.00 energy = 1.00000000
β = 2.00 energy = 1.00000000
β = 3.00 energy = 1.00000000
β = 4.00 energy = 1.00000000
β = 5.00 energy = 1.00000000
β = 6.00 energy = 1.00000000
β = 7.00 energy = 1.00000000
β = 8.00 energy = 1.00000000
β = 9.00 energy = 1.00000000
β = 10.00 energy = 1.00000000

goerch · April 7, 2022, 6:02am

Oops, I get ERROR: UndefVarError: @printf not defined on Julia 1.9.0?

yashi · April 7, 2022, 6:06am

My bad. You need

using Printf

And I’ve fixed it. Thanks @goerch !

goerch · April 7, 2022, 6:07am

Might be OP’s problem then, too

_SACHIN · April 7, 2022, 6:10am

no, I am using “using Printf”

FrancisKing · April 7, 2022, 8:48am

The difference between @_SACHIN and @yashi is the line energy = inner(rho.H). The code blocks are not the same.

What is the value of energy?

yashi · April 7, 2022, 12:29pm

using ITensors
using Printf
function ITensors.op(::OpName"expτSS", ::SiteType"S=1/2", s1::Index, s2::Index; τ)
    h =
        1 / 2 * op("S+", s1) * op("S-", s2) +
        1 / 2 * op("S-", s1) * op("S+", s2) +
        op("Sz", s1) * op("Sz", s2)
    return exp(τ * h)
end
function main(; N=10, cutoff=1E-8, δτ=0.1, beta_max=2.0)
    s = siteinds("S=1/2", N; conserve_qns=true)
    gates = ops([("expτSS", (n, n + 1), (τ=-δτ / 2,)) for n in 1:(N - 1)], s)
    append!(gates, reverse(gates))
    rho = MPO(s, "Id") ./ √2
    terms = OpSum()
    for j in 1:(N - 1)
        terms += 1 / 2, "S+", j, "S-", j + 1
        terms += 1 / 2, "S-", j, "S+", j + 1
        terms += "Sz", j, "Sz", j + 1
    end
    H = MPO(terms, s)
    for β in 0:δτ:beta_max
        energy = inner(rho, H)
        @printf("β = %.2f energy = %.8f\n", β, energy)
        rho = apply(gates, rho; cutoff)
        rho = rho / tr(rho)
    end
    return nothing
end

julia> main()
β = 0.00 energy = 0.00000000
β = 0.10 energy = -0.17283071
β = 0.20 energy = -0.35297829
β = 0.30 energy = -0.53907929
β = 0.40 energy = -0.72957328
β = 0.50 energy = -0.92249295
β = 0.60 energy = -1.11609434
β = 0.70 energy = -1.30848387
β = 0.80 energy = -1.49784914
β = 0.90 energy = -1.68252460
β = 1.00 energy = -1.86105195
β = 1.10 energy = -2.03222170
β = 1.20 energy = -2.19509440
β = 1.30 energy = -2.34900281
β = 1.40 energy = -2.49353817
β = 1.50 energy = -2.62853829
β = 1.60 energy = -2.75405200
β = 1.70 energy = -2.87026069
β = 1.80 energy = -2.97746496
β = 1.90 energy = -3.07607951
β = 2.00 energy = -3.16658443

julia>

_SACHIN · April 12, 2022, 5:00am

Hey, How you are able to get the results successfully.

I am not able to get that.

β = 0.00 energy = 0.00000000 
ERROR: LoadError: MethodError: no method matching /(::MPO, ::Float64)
Closest candidates are:
/(::StridedArray{P, N} where N, ::Real) where P<:Dates.Period at /buildworker/worker    
/package_linux64/build/usr/share/julia/stdlib/v1.6/Dates/src/deprecated.jl:44
/(::Union{SparseArrays.SparseVector{Tv, Ti}, SubArray{Tv, 1, var"#s814",      
Tuple{Base.Slice{Base.OneTo{Int64}}, Int64}, false} where var"#s814"     
<:SparseArrays.AbstractSparseMatrixCSC{Tv, Ti}, SubArray{Tv, 1, var"#s814",  
Tuple{Base.Slice{Base.OneTo{Int64}}}, false} where var"#s814"     
<:SparseArrays.AbstractSparseVector{Tv, Ti}} where {Tv, Ti}, ::Number) at /buildworker/worker/   
package_linux64/build/usr/share/julia/stdlib/v1.6/SparseArrays/src/sparsevector.jl:1450
 /(::Complex, ::Real) at complex.jl:333

 ...
    
Stacktrace:
 [1] main(; N::Int64, cutoff::Float64, δτ::Float64, beta_max::Float64)
 @ Main /media/sachin/data/sachin/chumbak/simulations/itensors/scripts_org/test_p.jl:26
 [2] main()
  @ Main /media/sachin/data/sachin/chumbak/simulations/itensors/scripts_org/test_p.jl:11
 [3] top-level scope
 @ /media/sachin/data/sachin/chumbak/simulations/itensors/scripts_org/test_p.jl:30

goerch · April 12, 2022, 5:13am

Because the code you are running (I suppose it is the one you posted on stackoverflow) is substantially different from @yashi’s (which works for me).

Edit: added diff

_SACHIN · April 12, 2022, 5:24am

No, I don’t think both are different. Btw, I also tried to run the same code which is posted here, and getting the same error. Could you please see to it.

_SACHIN · April 12, 2022, 5:45am

@goerch

See if run the same as it is in yashi, then also I get the same error.

 using ITensors
 using Printf
 function ITensors.op(::OpName"expτSS", ::SiteType"S=1/2", s1::Index, s2::Index; τ)
     h =
          1 / 2 * op("S+", s1) * op("S-", s2) +
          1 / 2 * op("S-", s1) * op("S+", s2) +
          op("Sz", s1) * op("Sz", s2)
       return exp(τ * h)
 end
 function main(; N=10, cutoff=1E-8, δτ=0.1, beta_max=2.0)
 s = siteinds("S=1/2", N; conserve_qns=true)
 gates = ops([("expτSS", (n, n + 1), (τ=-δτ / 2,)) for n in 1:(N - 1)], s)
 append!(gates, reverse(gates))
 rho = MPO(s, "Id") ./ √2
 terms = OpSum()
 for j in 1:(N - 1)
     terms += 1 / 2, "S+", j, "S-", j + 1
    terms += 1 / 2, "S-", j, "S+", j + 1
    terms += "Sz", j, "Sz", j + 1
end
H = MPO(terms, s)
for β in 0:δτ:beta_max
    energy = inner(rho, H)
    @printf("β = %.2f energy = %.8f\n", β, energy)
    rho = apply(gates, rho; cutoff)
    rho = rho / tr(rho)
end
return nothing
end
main()

_SACHIN · April 12, 2022, 5:46am

Pl tell me whether you are able to run the same ?

goerch · April 12, 2022, 5:51am

I copied the code you just posted, pasted and saved it to a new file and include-d it in the REPL. This works for me without problems.

Could you show us the error you are seeing somehow?

_SACHIN · April 12, 2022, 6:04am

See the error : https://stackoverflow.com/questions/71837797/getting-an-error-in-running-a-julia-program

goerch · April 12, 2022, 6:12am

OK, when I run the stack overflow code I first get

ERROR: UndefVarError: H not defined

for

 @show inner(rho, H)

Removing that line I then see

ERROR: MethodError: no method matching *(::MPO, ::typeof(main))

here

  rho = apply(gates, rho; cutoff)main

Removing main from that line

  rho = apply(gates, rho; cutoff)

makes the program work for me.

_SACHIN · April 12, 2022, 6:30am

oh! that was a typo in stackoverflow code.

I am getting the same error. could you please see the error and let me possibilities for it ?

_SACHIN · April 12, 2022, 7:06am

Same program is working in REPL

but why now not on my computer ?

_SACHIN · April 12, 2022, 11:10am

@goerch Looks like I have old version of itensors.