fix addition of DerivativeCoefficientRows with different Start values (#260)

* fix adding DerivativeCoefficientRows with different Start values

* added unit tests for DerivativeCoefficientRow

* move tests to new file

* bump version

---------

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

Author: Dougal-s

Project.toml

@@ -1,7 +1,7 @@
 name = "SummationByPartsOperators"
 uuid = "9f78cca6-572e-554e-b819-917d2f1cf240"
 author = ["Hendrik Ranocha"]
-version = "0.5.59"
+version = "0.5.60"
 
 [deps]
 ArgCheck = "dce04be8-c92d-5529-be00-80e4d2c0e197"

src/SBP_operators.jl

@@ -141,11 +141,11 @@ function Base.:+(coef_row1::DerivativeCoefficientRow{T,Start1,Length1}, coef_row
     Length = End - Start
     row = SVector{Length,T}(ntuple(i -> zero(T), Length))
     for i in 1:Length1
-        j = i-Start1+Start
+        j = i+Start1-Start
         row = Base.setindex(row, row[j] + coef_row1.coef[i], j)
     end
     for i in 1:Length2
-        j = i-Start2+Start
+        j = i+Start2-Start
         row = Base.setindex(row, row[j] + coef_row2.coef[i], j)
     end
     DerivativeCoefficientRow{T,Start,Length}(row)

test/runtests.jl

@@ -4,6 +4,7 @@ const SBP_TEST = get(ENV, "SBP_TEST", "all")
 
 @time @testset "SummationByPartsOperators.jl tests" begin
     @time if SBP_TEST == "all" || SBP_TEST == "part1"
+        @time @testset "Unit Tests" begin include("unit_tests.jl") end
         @time @testset "Periodic Operators" begin include("periodic_operators_test.jl") end
         @time @testset "Non-Periodic Operators" begin include("SBP_operators_test.jl") end
         @time @testset "Dissipation Operators" begin include("dissipation_operators_test.jl") end

test/unit_tests.jl

@@ -0,0 +1,23 @@
+using Test
+using SummationByPartsOperators
+
+@testset "DerivativeCoefficientRow" begin
+    row1 = SummationByPartsOperators.DerivativeCoefficientRow{Rational,1,3}([1,2,3])
+    row2 = SummationByPartsOperators.DerivativeCoefficientRow{Rational,1,3}([2,4,6])
+    row3 = SummationByPartsOperators.DerivativeCoefficientRow{Rational,2,3}([2,4,6])
+
+    @test -row1 ==
+        SummationByPartsOperators.DerivativeCoefficientRow{Rational,1,3}([-1,-2,-3])
+
+    @test row1 + row2 ==
+        SummationByPartsOperators.DerivativeCoefficientRow{Rational,1,3}([3,6,9])
+
+    @test row1 + row3 ==
+        SummationByPartsOperators.DerivativeCoefficientRow{Rational,1,4}([1,4,7,6])
+
+    @test row1 / 2 ==
+        SummationByPartsOperators.DerivativeCoefficientRow{Rational,1,3}([1//2, 2//2, 3//2])
+
+    @test (row1 + -row3) / 2 ==
+        SummationByPartsOperators.DerivativeCoefficientRow{Rational,1,4}([1//2, 0, -1//2, -3])
+end