Make error norm calculation optional (#1755)

* Make error norm calculation optional

* test no errors

* no errors

* comment more clear

* shorter version?

* add text

* update docstring

* cut error passing

* Update src/callbacks_step/analysis.jl

Co-authored-by: Hendrik Ranocha <[email protected]>

* print in if clause

* shorten

* Update src/callbacks_step/analysis.jl

Co-authored-by: Hendrik Ranocha <[email protected]>

* Add docstring for default_analysis_errors

* Update src/equations/equations.jl

---------

Co-authored-by: Hendrik Ranocha <[email protected]>

src/callbacks_step/analysis.jl

@@ -23,6 +23,13 @@ Additional errors can be computed, e.g. by passing
 `extra_analysis_errors = (:l2_error_primitive, :linf_error_primitive)`
 or `extra_analysis_errors = (:conservation_error,)`.
 
+If you want to omit the computation (to safe compute-time) of the [`default_analysis_errors`](@ref), specify
+`analysis_errors = Symbol[]`.
+Note: `default_analysis_errors` are `:l2_error` and `:linf_error` for all equations.
+If you want to compute `extra_analysis_errors` such as `:conservation_error` solely, i.e., 
+without `:l2_error, :linf_error` you need to specify 
+`analysis_errors = [:conservation_error]` instead of `extra_analysis_errors = [:conservation_error]`.
+
 Further scalar functions `func` in `extra_analysis_integrals` are applied to the numerical
 solution and integrated over the computational domain. Some examples for this are
 [`entropy`](@ref), [`energy_kinetic`](@ref), [`energy_internal`](@ref), and [`energy_total`](@ref).
@@ -332,7 +339,8 @@ function (analysis_callback::AnalysisCallback)(u_ode, du_ode, integrator, semi)
         @notimeit timer() integrator.f(du_ode, u_ode, semi, t)
         u = wrap_array(u_ode, mesh, equations, solver, cache)
         du = wrap_array(du_ode, mesh, equations, solver, cache)
-        l2_error, linf_error = analysis_callback(io, du, u, u_ode, t, semi)
+        # Compute l2_error, linf_error
+        analysis_callback(io, du, u, u_ode, t, semi)
 
         mpi_println("─"^100)
         mpi_println()
@@ -354,8 +362,7 @@ function (analysis_callback::AnalysisCallback)(u_ode, du_ode, integrator, semi)
     analysis_callback.start_time_last_analysis = time_ns()
     analysis_callback.ncalls_rhs_last_analysis = ncalls(semi.performance_counter)
 
-    # Return errors for EOC analysis
-    return l2_error, linf_error
+    return nothing
 end
 
 # This method is just called internally from `(analysis_callback::AnalysisCallback)(integrator)`
@@ -377,28 +384,31 @@ function (analysis_callback::AnalysisCallback)(io, du, u, u_ode, t, semi)
         println()
     end
 
-    # Calculate L2/Linf errors, which are also returned
-    l2_error, linf_error = calc_error_norms(u_ode, t, analyzer, semi, cache_analysis)
+    if :l2_error in analysis_errors || :linf_error in analysis_errors
+        # Calculate L2/Linf errors
+        l2_error, linf_error = calc_error_norms(u_ode, t, analyzer, semi,
+                                                cache_analysis)
 
-    if mpi_isroot()
-        # L2 error
-        if :l2_error in analysis_errors
-            print(" L2 error:    ")
-            for v in eachvariable(equations)
-                @printf("  % 10.8e", l2_error[v])
-                @printf(io, "  % 10.8e", l2_error[v])
+        if mpi_isroot()
+            # L2 error
+            if :l2_error in analysis_errors
+                print(" L2 error:    ")
+                for v in eachvariable(equations)
+                    @printf("  % 10.8e", l2_error[v])
+                    @printf(io, "  % 10.8e", l2_error[v])
+                end
+                println()
             end
-            println()
-        end
 
-        # Linf error
-        if :linf_error in analysis_errors
-            print(" Linf error:  ")
-            for v in eachvariable(equations)
-                @printf("  % 10.8e", linf_error[v])
-                @printf(io, "  % 10.8e", linf_error[v])
+            # Linf error
+            if :linf_error in analysis_errors
+                print(" Linf error:  ")
+                for v in eachvariable(equations)
+                    @printf("  % 10.8e", linf_error[v])
+                    @printf(io, "  % 10.8e", linf_error[v])
+                end
+                println()
             end
-            println()
         end
     end
 
@@ -477,7 +487,7 @@ function (analysis_callback::AnalysisCallback)(io, du, u, u_ode, t, semi)
     # additional integrals
     analyze_integrals(analysis_integrals, io, du, u, t, semi)
 
-    return l2_error, linf_error
+    return nothing
 end
 
 # Print level information only if AMR is enabled

src/equations/equations.jl

@@ -260,7 +260,14 @@ combined with certain solvers (e.g., subcell limiting).
 function n_nonconservative_terms end
 have_constant_speed(::AbstractEquations) = False()
 
+"""
+    default_analysis_errors(equations)
+
+Default analysis errors (`:l2_error` and `:linf_error`) used by the
+[`AnalysisCallback`](@ref).
+"""
 default_analysis_errors(::AbstractEquations) = (:l2_error, :linf_error)
+
 """
     default_analysis_integrals(equations)
 

test/test_tree_1d_advection.jl

@@ -54,6 +54,20 @@ end
     end
 end
 
+@trixi_testset "elixir_advection_basic.jl (No errors)" begin
+    @test_trixi_include(joinpath(EXAMPLES_DIR, "elixir_advection_basic.jl"),
+                        analysis_callback=AnalysisCallback(semi, interval = 42,
+                                                           analysis_errors = Symbol[]))
+    # Ensure that we do not have excessive memory allocations
+    # (e.g., from type instabilities)
+    let
+        t = sol.t[end]
+        u_ode = sol.u[end]
+        du_ode = similar(u_ode)
+        @test (@allocated Trixi.rhs!(du_ode, u_ode, semi, t)) < 1000
+    end
+end
+
 @trixi_testset "elixir_advection_finite_volume.jl" begin
     @test_trixi_include(joinpath(EXAMPLES_DIR, "elixir_advection_finite_volume.jl"),
                         l2=[0.011662300515980219],