DMRG Callback (#304)

Co-authored-by: Matt Fishman <mtfishman@users.noreply.github.com>

Author: emstoudenmire

Project.toml

@@ -1,6 +1,6 @@
 name = "ITensorNetworks"
 uuid = "2919e153-833c-4bdc-8836-1ea460a35fc7"
-version = "0.15.25"
+version = "0.15.26"
 authors = ["Matthew Fishman <mfishman@flatironinstitute.org>, Joseph Tindall <jtindall@flatironinstitute.org> and contributors"]
 
 [workspace]

src/solvers/eigsolve.jl

@@ -97,7 +97,8 @@ energy, psi = eigsolve(H, psi0;
 See also: [`dmrg`](@ref), [`time_evolve`](@ref).
 """
 function eigsolve(
-        operator, init_state; nsweeps, nsites = 1, factorize_kwargs, sweep_kwargs...
+        operator, init_state; nsweeps, nsites = 1, factorize_kwargs,
+        sweep_callback = default_sweep_callback, sweep_kwargs...
     )
     init_prob = EigsolveProblem(;
         state = align_indices(init_state), operator = ProjTTN(align_indices(operator))
@@ -110,7 +111,7 @@ function eigsolve(
         subspace_expand!_kwargs = (; eigen_kwargs = factorize_kwargs),
         sweep_kwargs...
     )
-    prob = problem(sweep_solve!(sweep_iter))
+    prob = problem(sweep_solve!(sweep_callback, sweep_iter))
     return eigenvalue(prob), state(prob)
 end
 

test/solvers/test_eigsolve.jl

@@ -1,6 +1,6 @@
 using Graphs: dst, edges, src, vertices
 using ITensorMPS: OpSum
-using ITensorNetworks: dmrg, siteinds, ttn
+using ITensorNetworks: SweepIterator, dmrg, siteinds, ttn
 using ITensors
 using Suppressor: @capture_out
 using TensorOperations: TensorOperations
@@ -73,6 +73,17 @@ include("utilities/tree_graphs.jl")
     (outputlevel >= 1) && println("2-site DMRG energy = ", E)
     @test E ≈ Ex atol = 1.0e-5
 
+    #
+    # Test ability to pass custom sweep_callback
+    # (Regression test for PR #304)
+    #
+    sweep_count = 0
+    function sweep_callback(sweep_iter::SweepIterator; kws...)
+        return sweep_count += 1
+    end
+    dmrg(H, psi0; factorize_kwargs, nsweeps, outputlevel, sweep_callback)
+    @test sweep_count == nsweeps
+
     #
     # Test that outputlevel > 0 generates output
     # and outputlevel == 0 generates no output