Update the documentation for KrylovConstructor

docs/src/custom_workspaces.md

@@ -1,3 +1,5 @@
+# [Custom workspaces](@id custom_workspaces)
+
 ## Custom workspaces for the Poisson equation with halo regions
 
 ### Introduction

docs/src/inplace.md

@@ -3,15 +3,24 @@
 All solvers in Krylov.jl have an in-place variant implemented in a method whose name ends with `!`.
 A workspace (`KrylovSolver`), which contains the storage needed by a Krylov method, can be used to solve multiple linear systems with the same dimensions and the same floating-point precision.
 The section [storage requirements](@ref storage-requirements) specifies the memory needed for each Krylov method.
-Each `KrylovSolver` has two constructors:
+Each `KrylovSolver` has three constructors:
 
 ```@constructors
 XyzSolver(A, b)
 XyzSolver(m, n, S)
+XyzSolver(kc::KrylovConstructor)
 ```
 
-`Xyz` is the name of the Krylov method with lowercase letters except its first one (`Cg`, `Minres`, `Lsmr`, `Bicgstab`, ...).
-Given an operator `A` and a right-hand side `b`, you can create a `KrylovSolver` based on the size of `A` and the type of `b` or explicitly give the dimensions `(m, n)` and the storage type `S`.
+`Xyz` represents the name of the Krylov method, written in lowercase except for its first letter (e.g., `Cg`, `Minres`, `Lsmr`, `Bicgstab`, etc.).
+If the name of the Krylov method contains an underscore (e.g., `minres_qlp` or `cgls_lanczos_shift`), the workspace constructor transforms it by capitalizing each word and removing underscores, resulting in names like `MinresQlpSolver` or `CglsLanczosShiftSolver`.
+
+Given an operator `A` and a right-hand side `b`, you can create a `KrylovSolver` based on the size of `A` and the type of `b`, or explicitly provide the dimensions `(m, n)` and the storage type `S`.
+We assume that `S(undef, 0)`, `S(undef, n)`, and `S(undef, m)` are well-defined for the storage type `S`.
+For more advanced vector types, workspaces can also be created with the help of a `KrylovConstructor`.
+```@docs
+Krylov.KrylovConstructor
+```
+See the section [custom workspaces](@ref custom_workspaces) for an example where this constructor is the only applicable option.
 
 For example, use `S = Vector{Float64}` if you want to solve linear systems in double precision on the CPU and `S = CuVector{Float32}` if you want to solve linear systems in single precision on an Nvidia GPU.
 

src/block_krylov_solvers.jl

@@ -15,7 +15,6 @@ The outer constructors
 
     solver = BlockMinresSolver(m, n, p, SV, SM)
     solver = BlockMinresSolver(A, B)
-    solver = BlockMinresSolver(kc::BlockKrylovConstructor)
 
 may be used in order to create these vectors.
 `memory` is set to `div(n,p)` if the value given is larger than `div(n,p)`.
@@ -83,7 +82,6 @@ The outer constructors
 
     solver = BlockGmresSolver(m, n, p, memory, SV, SM)
     solver = BlockGmresSolver(A, B, memory = 5)
-    solver = BlockGmresSolver(kc::BlockKrylovConstructor, memory = 5)
 
 may be used in order to create these vectors.
 `memory` is set to `div(n,p)` if the value given is larger than `div(n,p)`.