Fix off-by-one error in iteration count of IDR(s) (#158)

* Fix off-by-one error in iteration count

* Add test for # of iterations in IDR(s)

Author: haampie

src/idrs.jl

@@ -51,7 +51,7 @@ function idrs_method!(log::ConvergenceHistory, X, op, args, C::T,
     verbose && @printf("=== idrs ===\n%4s\t%7s\n","iter","resnorm")
     R = C - op(X, args...)::T
     normR = vecnorm(R)
-	iter = 0
+	iter = 1
 
     if smoothing
         X_s = copy(X)
@@ -76,7 +76,7 @@ function idrs_method!(log::ConvergenceHistory, X, op, args, C::T,
     c = zeros(eltype(C),s)
 
     om::eltype(C) = 1
-    while normR > tol && iter < maxiter
+    while normR > tol && iter ≤ maxiter
         for i in 1:s,
             f[i] = vecdot(P[i], R)
         end
@@ -144,16 +144,15 @@ function idrs_method!(log::ConvergenceHistory, X, op, args, C::T,
             end
             push!(log, :resnorm, normR)
             verbose && @printf("%3d\t%1.2e\n",iter,normR)
-            iter += 1
-            if normR < tol || iter > maxiter
+            if normR < tol || iter == maxiter
                 shrink!(log)
                 setconv(log, 0<=normR<tol)
                 return X
             end
             if k < s
                 f[k+1:s] = f[k+1:s] - beta*M[k+1:s,k]
             end
-
+            iter += 1
         end
 
         # Now we have sufficient vectors in G_j to compute residual in G_j+1

test/idrs.jl

@@ -35,4 +35,10 @@ end
     @test history.isconverged
     @test norm(A * x - b) / norm(b) ≤ tol
 end
+
+@testset "Maximum number of iterations" begin
+    x, history = idrs(rand(5, 5), rand(5), log=true, maxiter=2)
+    @test history.iters == 2
+    @test length(history[:resnorm]) == 2
+end
 end