branch: externals/el-job
commit 01755351dbfadfe3cb0c3efa30b36f0e0becb0f5
Author: Martin Edström <[email protected]>
Commit: Martin Edström <[email protected]>
Add el-job-parallel-mapcar
---
el-job-ng.el | 5 ++++-
el-job.el | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 53 insertions(+), 1 deletion(-)
diff --git a/el-job-ng.el b/el-job-ng.el
index 673b3a1a43..b4d57232a5 100644
--- a/el-job-ng.el
+++ b/el-job-ng.el
@@ -273,6 +273,7 @@ ID can also be passed to these helpers:
;;; Code used by child processes
+(defvar el-job-ng--child-unary nil)
(defun el-job-ng--child-work ()
(let* ((coding-system-for-write 'utf-8-emacs-unix)
(coding-system-for-read 'utf-8-emacs-unix)
@@ -291,7 +292,9 @@ ID can also be passed to these helpers:
(eval form t))
(while-let ((input (pop inputs)))
(let ((start (current-time))
- (output (funcall func input inputs)))
+ (output (if el-job-ng--child-unary
+ (funcall func input)
+ (funcall func input inputs))))
(push (list input (time-since start) output) benchmarked-outputs)))
(let ((print-length nil)
(print-level nil)
diff --git a/el-job.el b/el-job.el
index 91c4909ca3..3140ebde98 100644
--- a/el-job.el
+++ b/el-job.el
@@ -81,6 +81,55 @@
(defvar el-jobs :obsolete)
+
+;;;; Mapcar-like entry-point
+
+(defvar el-job--synchronous-result nil)
+(defun el-job-parallel-mapcar (fn list &optional inject-vars)
+ "Apply FN to LIST like `mapcar' in one or more parallel processes.
+
+Function FN must be known in `load-history' to be defined in some file.
+The parallel processes inherit `load-path' and then load that file.
+
+Function FN must not depend on side effects from previous invocations of
+itself, because each process gets a different subset of LIST.
+
+Unlike the more general `el-job-ng-run', this is meant as a close
+drop-in for `mapcar'. It behaves like a synchronous function by
+blocking execution until the processes are done, then returns the
+result to the caller.
+
+Quitting kills the processes, much like quitting would interrupt a
+synchronous function.
+
+INJECT-VARS as in `el-job-ng-run'.
+
+For convenience, INJECT-VARS can contain bare symbols instead of cons
+cells, because it is processed by `el-job-ng-vars'.
+
+N/B: A crucial difference from `mapcar' is the temporary loss of scope,
+since FN runs in external processes.
+That means FN will not see let-bindings, runtime variables and the like,
+that you might have meant to have in effect where
+`el-job-parallel-mapcar' is invoked.
+Nor can it mutate such variables for you -- the only way it can affect
+the current Emacs session is if the caller of
+`el-job-parallel-mapcar' does something with the return value."
+ (let* ((vars (el-job-ng-vars (cons '(el-job-ng--child-unary . t)
inject-vars)))
+ (id (intern (format "parallel-mapcar.%S.%d" fn (sxhash vars)))))
+ (el-job-ng-run
+ :id id
+ :require (unless (subr-primitive-p (symbol-function fn)) ;; Emacs 28
+ (list (symbol-file fn 'defun t)))
+ :inject-vars vars
+ :funcall-per-input fn
+ :inputs list
+ :callback (lambda (outputs)
+ (setq el-job--synchronous-result outputs)))
+ (unless (el-job-ng-await-or-die id 86400)
+ (error "el-job-ng-parallel-mapcar: Timed out (hung for 24 hours): %S"
fn))
+ el-job--synchronous-result))
+
(provide 'el-job)
;;; el-job.el ends here
