From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Fri, 27 Apr 2012 11:22:19 +0000 (+0100)
Subject: strategy: wip, notation changes, finished planning we think
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=topbloke-formulae.git;a=commitdiff_plain;h=edd89d19f03e82b54c2999319ac48fe20173ff6e

strategy: wip, notation changes, finished planning we think
---

diff --git a/article.tex b/article.tex
index 02bf4ce..b37edd5 100644
--- a/article.tex
+++ b/article.tex
@@ -95,6 +95,15 @@
 \newcommand{\eqntag}[2]{ #2 \tag*{\mbox{#1}} }
 \newcommand{\eqn}[2]{ #2 \tag*{\mbox{\bf #1}} }
 
+\newcommand{\hasdirdep}{\succ_{\mkern-7.0mu _1}}
+\newcommand{\hasdep}{\succ}
+\newcommand{\isdep}{\prec}
+
+\newcommand{\grefzc}{ T^0_{\pc} }
+\newcommand{\grefcc}{ T_{\pc} }
+\newcommand{\grefuc}{ T'_{\pc} }
+\newcommand{\greffc}{ T^*_{\pc} }
+
 %\newcommand{\bigforall}{\mathop{\hbox{\huge$\forall$}}}
 \newcommand{\bigforall}{%
   \mathop{\mathchoice%
diff --git a/strategy.tex b/strategy.tex
index 4cd80db..a718aec 100644
--- a/strategy.tex
+++ b/strategy.tex
@@ -13,63 +13,93 @@ for $\patchof{L}$.
 The set of direct dependencies (in the form $\py$)
 requested in the commit $K$ ($K \in \pn$) for the patch $\p$.
 
-\item[ $\pc \succ_1 \{ \p, \pq \ldots \}$ ]
-The Topbloke commit set $\pc$ has as direct contributors
-(see below) exactly $\p, \pq, \ldots$.  This is an acyclic relation.
+\item[ $\pc \hasdirdep \p$ ]
+The Topbloke commit set $\pc$ has as a direct contributors the
+commit set $\p$.  This is an acyclic relation.
 
-\item[ $\p \succ \pq$ ]
+\item[ $\p \hasdep \pq$ ]
 The commit set $\p$ has as direct or indirect contributor the commit
 set $\pq$.
-This is an acyclic relation, and is the completion of $\succ_1$ into a
+Acyclic; the completion of $\hasdirdep$ into a
 partial order.
 
 \item[ $\set E_{\pc}$ ]
 $ \bigcup_i \pendsof{S_i}{\pc} $.
 All the ends of $\pc$ in the sources.
 
+\item[ $ \grefzc, \grefcc, \grefuc, \greffc $ ]
+The git ref for the Topbloke commit set $\pc$: respectively,
+the original, current, updated, and final values.
+
 \end{basedescript}
 
 \section{Planning phase}
 
+The planning phase computes: 
+\begin{itemize*}
+\item{ The relation $\hasdirdep$ and hence the ordering $\hasdep$. }
+\item{ For each commit set $\pc$, the order in which to merge
+        $E_{\pc,j} \in \set E_{\pc}$. }
+\item{ For each $E_{\pc,j}$ an intended merge base $M_{\pc,j}$. }
+\end{itemize*}
+
 We use a recursive planning algorith, recursing over Topbloke commit
 sets (ie, sets $\py$ or $\pn$).  We'll call the commit set we're
-processing at each step $\pc$.  We start with $\pc = \pl$
-where $\pl = \patchof{L}$.
-
+processing at each step $\pc$.
 At each recursive step 
-we intend to merge all $\set E_{\pc} = \{ E_{\pc,j \ldots} \}$
+we make a plan to merge all $\set E_{\pc} = \{ E_{\pc,j \ldots} \}$
 and all the direct contributors of $\pc$ (as determined below)
-into the existing git ref for $\pc$, to make $T_{\pc}$.
-The direct contributors of $\pcn$ are the Topbloke commit sets
-corresponding to the tip branches for the direct dependencies of
-$\pc$.
-The sole direct contributor of $\pcy$ is $\pcn$.
+into $\grefzc$, to make $\greffc$.
+
+We start with $\pc = \pl$ where $\pl = \patchof{L}$.
+
 
-\subsection{Planning step for $\pc = \pcn$.}
+\subsection{Direct contributors for $\pc = \pcn$}
+
+The direct contributors of $\pcn$ are the commit sets corresponding to
+the tip branches for the direct dependencies of the patch $\pc$.  We
+need to calculate what the direct dependencies are going to be.
 
 Choose an (arbitrary, but ideally somehow optimal in
-a way not discussed here) ordering of $\set E_{\pc}$, $E_j$ (for
-$j = 1 \ldots m$).  Remove from that set (and ordering) any $E_j$ which
+a way not discussed here) ordering of $\set E_{\pc}$, $E_{\pc,j}$
+($j = 1 \ldots m$).
+For brevity we will write $E_j$ for $E_{\pc,j}$.
+Remove from that set (and ordering) any $E_j$ which
 are $\le$ and $\neq$ some other $E_k$.
 
-Initially let $T_{\pc,0}$ be the git ref for $\pcn$.  And let
-$\set D_0 = \depsreqof{T_{\pc,0}}$.
+Initially let $\set D_0 = \depsreqof{\grefzc}$.
 For each $E_j$ starting with $j=1$ choose a corresponding intended
 merge base $M_j$ such that $M_j \le E_j \land M_j \le T_{\pc,j-1}$.
 Calculate $\set D_j$ as the 3-way merge of the sets $\set D_{j-1}$ and
 $\depsreqof{E_j}$ using as a base $\depsreqof{M_j}$.  This will
-generate $D_m$ as the putative direct contributors for $\pcn$.
+generate $D_m$ as the putative direct contributors of $\pcn$.
+
+However, the invocation may give instructions that certain direct
+dependencies are definitely to be included, or excluded.  As a result
+the set of actual direct contributors is some arbitrary set of patches
+(strictly, some arbitrary set of Topbloke tip commit sets).
+
+\subsection{Direct contributors for $\pc = \pcy$}
+
+The sole direct contributor of $\pcy$ is $\pcn$.
+
+\subsection{Recursive step}
 
-However, the invocation may specify that certain direct dependencies
-are definitely to be included, or excluded.  As a result the set
-of actual direct contributors is some arbitrary set of patches.
+For each direct contributor $\p$, we add the edge $\pc \hasdirdep \p$
+and augment the ordering $\hasdep$ accordingly.
 
+If this would make a cycle in $\hasdep$, we abort . The operation must
+then be retried by the user, if desired, but with different or
+additional instructions for modifying the direct contributors of some
+$\pqn$ involved in the cycle.
 
+For each such $\p$, after updating $\hasdep$, we recursively make a plan
+for $\pc' = \p$.
 
+\section{Execution phase}
 
 
 
-Imagine that we will merge the direct 
 
 with $M=M_j, L=T_{\pc,j-1}, R=E_j$,
 and calculate what the resulting desired direct dependencies file