[PATCH 3 of 5] revsbetween: add a C implementation

Laurent Charignon lcharignon at fb.com
Fri Aug 7 04:25:41 CDT 2015


On Aug 7, 2015, at 12:41 AM, Pierre-Yves David <pierre-yves.david at ens-lyon.org<mailto:pierre-yves.david at ens-lyon.org>> wrote:



On 08/06/2015 11:10 PM, Laurent Charignon wrote:
# HG changeset patch
# User Laurent Charignon <lcharignon at fb.com<mailto:lcharignon at fb.com>>
# Date 1438921725 25200
#      Thu Aug 06 21:28:45 2015 -0700
# Branch stable
# Node ID 074dd6f6412076af9704bc9848c97d4c647f330d
# Parent  c0fc894d0539cb526724b1cd15488ee6dd9314ff
revsbetween: add a C implementation

This patch is part of a series of patches to speed up the computation of
revset.revsbetween by introducing a C implementation. The main motivation is to
speed up smartlog on big repositories. At the end of the series, on our big
repositories the computation of revsbetween is 10-50x faster and smartlog on is
2x-5x faster.

This patch introduces a C implementation for revsbetween following closely the
Python implementation but optimized by using C data structures.

The logic seems good to me but I've a couple of comment inline. I also would like someone with more Cpython experience to look at this.


diff --git a/mercurial/parsers.c b/mercurial/parsers.c
--- a/mercurial/parsers.c
+++ b/mercurial/parsers.c
@@ -1105,6 +1105,136 @@
  phases[i] = phases[parent_2];
 }

+static PyObject *revsbetween(indexObject *self, PyObject *args)
+{
+
+ /* Input */
+ long minroot;
+ PyObject *onlyrootsarg = NULL;
+ int onlyroots = 0;
+ PyObject *heads = NULL;
+ Py_ssize_t numheads;
+ PyObject *roots = NULL;
+ PyObject *reachable = NULL;
+
+ PyObject *val;
+ Py_ssize_t len = index_length(self) - 1;
+ long revnum;
+ Py_ssize_t k;
+ Py_ssize_t i;
+ int r;
+ int minidx;
+ int parents[2];
+
+ /* Internal data structure:
+  * tovisit: array of length len, filled upto lentovisit
+  * seen: array of length len+1 (because nullrev) 0: not seen, 1 seen*/
+ long *tovisit = NULL;
+ long lentovisit = 0;
+ char *seen = NULL;
+
+ /* Get arguments */
+ if (!PyArg_ParseTuple(args, "lOOO", &minroot, &heads, &roots, &onlyrootsarg))
+ goto bail;
+ if (roots == NULL || !PySet_Check(roots))
+ goto bail;
+ if (heads == NULL || !PyList_Check(heads))
+ goto bail;
+ if (onlyrootsarg == NULL || !PyBool_Check(onlyrootsarg))
+ goto bail;
+ if (onlyrootsarg == Py_True)
+ onlyroots = 1;
+
+ /* Initialize return set */
+ reachable = PySet_New(0);
+ if (reachable == NULL)
+ goto bail;
+
+ /* Initialize internal datastructures */
+ tovisit = (long *)malloc(2*len * sizeof(long));

Looks like you let a 2* in there.

Good catch, will fix it!

+ if (tovisit == NULL)
+ goto release_reachable;
+
+ seen = (char *)calloc(len+1, 1);
+ if (seen == NULL)
+ goto release_tovisit;

Can we get some more comment about what each of this failure mean?

Sure

+ /* Populate tovisit with all the heads */
+ numheads = PyList_GET_SIZE(heads);
+ for (i = 0; i < numheads; i++) {
+ revnum = PyInt_AS_LONG(PyList_GET_ITEM(heads, i));
+ if (seen[revnum+1] == 0) {
+ tovisit[lentovisit++] = revnum;
+ seen[revnum+1]=1;
+ }
+ }
+
+ /* Visit the tovisit list and find the reachable roots */
+ k = 0;
+ while (k < lentovisit) {
+ /* Add the node to reachable if it is a root*/
+ revnum = tovisit[k++];
+ val = PyInt_FromLong(revnum);
+ if (PySet_Contains(roots, val) == 1) {
+ PySet_Add(reachable, val);
+ if (onlyroots == 1) {
+ Py_XDECREF(val);
+ continue;
+ }
+ }
+ Py_XDECREF(val);
+
+ /* And its parents to the list of nodes to visit */
+ if (revnum != -1) {
+ r = index_get_parents(self, revnum, parents, (int)len - 1);
+ if (r < 0)
+ goto release_seen;
+
+ for (i = 0; i < 2; i++) {
+ if (seen[parents[i]+1] == 0 && parents[i] >= minroot) {
+ tovisit[lentovisit++] = parents[i];
+ seen[parents[i]+1]=1;
+ }
+ }
+ }
+ }
+
+ /* Find all the nodes in between the roots we found and the heads
+  * and add them to the reachable set */
+ if (onlyroots == 0) {
+ minidx = minroot;
+ if (minidx < 0)
+ minidx = 0;
+ for (i = minidx; i < len; i++) {
+ if (seen[i+1] == 1) {
+ r = index_get_parents(self, i, parents, (int)len - 1);
+ if (r < 0)
+ goto release_seen;

Same feedback about explaining the error case.

Ok!

+ for (k = 0; k < 2; k++) {
+ PyObject *p = PyInt_FromLong(parents[k]);
+ if (PySet_Contains(reachable, p) == 1)
+ PySet_Add(reachable, PyInt_FromLong(i));
+ Py_XDECREF(p);
+ }
+ }
+ }
+ }
+
+release_seen:
+ if (seen != NULL)
+ free(seen);
+release_tovisit:
+ if (tovisit != NULL)
+ free(tovisit);
+ return reachable;
+release_reachable:
+ Py_XDECREF(reachable);
+bail:
+ val = Py_None;
+ Py_INCREF(Py_None);
+ return val;
+}
+
 static PyObject *compute_phases_map_sets(indexObject *self, PyObject *args)
 {
  PyObject *roots = Py_None;
@@ -2279,6 +2409,8 @@
   "get an index entry"},
  {"computephasesmapsets", (PyCFunction)compute_phases_map_sets,
  METH_VARARGS, "compute phases"},
+ {"revsbetween", (PyCFunction)revsbetween, METH_VARARGS,
+ "revsbetween"},
  {"headrevs", (PyCFunction)index_headrevs, METH_VARARGS,
   "get head revisions"}, /* Can do filtering since 3.2 */
  {"headrevsfiltered", (PyCFunction)index_headrevs, METH_VARARGS,
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--
Pierre-Yves David

Thanks for the quick review :)

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