Reuse memory for CG point in SYMMLQ

JuliaSmoothOptimizers · Mar 7, 2019 · 270d90d · 270d90d
1 parent ef0a34e
commit 270d90d
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Showing 2 changed files with 5 additions and 5 deletions.
diff --git a/src/symmlq.jl b/src/symmlq.jl
@@ -40,15 +40,14 @@ function symmlq(A :: AbstractLinearOperator, b :: AbstractVector{T};
 
   ϵM = eps(T)
   x_lq = zeros(T, n)
-  x_cg = zeros(T, n)
   ctol = conlim > 0.0 ? 1 / conlim : 0.0;
 
   # Initialize Lanczos process.
   # β₁ M v₁ = b.
   Mvold = copy(b)
   vold = M * Mvold
   β₁ = @kdot(m, vold, Mvold)
-  β₁ == 0.0 && return (x_lq, x_cg, SimpleStats(true, true, [0.0], [0.0], "x = 0 is a zero-residual solution"))
+  β₁ == 0.0 && return (x_lq, zeros(T, n), SimpleStats(true, true, [0.0], [0.0], "x = 0 is a zero-residual solution"))
   β₁ = sqrt(β₁)
   β = β₁
   @kscal!(m, 1 / β, vold)
@@ -263,7 +262,8 @@ function symmlq(A :: AbstractLinearOperator, b :: AbstractVector{T};
   end
 
   # Compute CG point
-  @. x_cg = x_lq + ζbar * wbar
+  @kaxpby!(m, 1.0, x_lq, ζbar, wbar)
+  x_cg = wbar
 
   tired         && (status = "maximum number of iterations exceeded")
   ill_cond_mach && (status = "condition number seems too large for this machine")

diff --git a/test/test_alloc.jl b/test/test_alloc.jl
@@ -11,8 +11,8 @@ mem = 10
 shifts  = [1:5;]
 nshifts = 5
 
-# without preconditioner and with Ap preallocated, SYMMLQ needs 6 n-vectors: x_lq, x_cg, vold, v, w, wbar
-storage_symmlq(n) = 6 * n
+# without preconditioner and with Ap preallocated, SYMMLQ needs 5 n-vectors: x_lq, vold, v, w, wbar
+storage_symmlq(n) = 5 * n
 storage_symmlq_bytes(n) = 8 * storage_symmlq(n)
 
 expected_symmlq_bytes = storage_symmlq_bytes(n)