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;;; Guix Data Service -- Information about Guix over time
;;; Copyright © 2020 Christopher Baines <mail@cbaines.net>
;;;
;;; This program is free software: you can redistribute it and/or
;;; modify it under the terms of the GNU Affero General Public License
;;; as published by the Free Software Foundation, either version 3 of
;;; the License, or (at your option) any later version.
;;;
;;; This program is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;; Affero General Public License for more details.
;;;
;;; You should have received a copy of the GNU Affero General Public
;;; License along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
(define-module (guix-data-service utils)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-11)
#:use-module (ice-9 match)
#:use-module (ice-9 threads)
#:use-module (fibers)
#:use-module (fibers channels)
#:use-module (fibers conditions)
#:export (call-with-time-logging
with-time-logging
prevent-inlining-for-tests
parallel-via-thread-pool-channel
par-map&
letpar&
chunk
chunk!
chunk-for-each!))
(define (call-with-time-logging action thunk)
(simple-format #t "debug: Starting ~A\n" action)
(let ((start-time (current-time)))
(let-values
((result (thunk)))
(let ((time-taken (- (current-time) start-time)))
(simple-format #t "debug: Finished ~A, took ~A seconds\n"
action time-taken))
(apply values result))))
(define-syntax-rule (with-time-logging action exp ...)
"Log under NAME the time taken to evaluate EXP."
(call-with-time-logging action (lambda () exp ...)))
(define-syntax-rule (prevent-inlining-for-tests var)
(set! var var))
(define* (make-thread-pool-channel #:key (threads 8))
(let ((channel (make-channel)))
(for-each
(lambda _
(call-with-new-thread
(lambda ()
(let loop ()
(match (get-message channel)
(((? channel? reply) . (? procedure? proc))
(put-message
reply
(with-exception-handler
(lambda (exn)
(cons 'worker-thread-error exn))
(lambda ()
(with-exception-handler
(lambda (exn)
(simple-format
(current-error-port)
"worker thread: exception: ~A\n"
exn)
(backtrace)
(raise-exception exn))
(lambda ()
(call-with-values
proc
(lambda vals
vals)))))
#:unwind? #t))
(loop))
(_ #f))))))
(iota threads))
channel))
(define %thread-pool-mutex (make-mutex))
(define %thread-pool-channel #f)
(define (make-thread-pool-channel!')
(with-mutex %thread-pool-mutex
(unless %thread-pool-channel
(set! %thread-pool-channel (make-thread-pool-channel))
(set! make-thread-pool-channel! (lambda () #t)))))
(define make-thread-pool-channel!
(lambda () (make-thread-pool-channel!')))
(define (defer-to-thread-pool-channel thunk)
(make-thread-pool-channel!)
(let ((reply (make-channel)))
(spawn-fiber
(lambda ()
(put-message %thread-pool-channel (cons reply thunk))))
reply))
(define (fetch-result-of-defered-thunk reply-channel)
(match (get-message reply-channel)
(('worker-thread-error . exn)
(raise-exception exn))
(result
(apply values result))))
(define (fetch-result-of-defered-thunks . reply-channels)
(let ((responses (map get-message reply-channels)))
(map
(match-lambda
(('worker-thread-error . exn)
(raise-exception exn))
(result
(apply values result)))
responses)))
(define-syntax parallel-via-thread-pool-channel
(lambda (x)
(syntax-case x ()
((_ e0 ...)
(with-syntax (((tmp0 ...) (generate-temporaries (syntax (e0 ...)))))
#'(let ((tmp0 (defer-to-thread-pool-channel
(lambda ()
e0)))
...)
(apply values (fetch-result-of-defered-thunks tmp0 ...))))))))
(define-syntax-rule (letpar& ((v e) ...) b0 b1 ...)
(call-with-values
(lambda () (parallel-via-thread-pool-channel e ...))
(lambda (v ...)
b0 b1 ...)))
(define (par-mapper' mapper cons)
(lambda (proc . lists)
(let loop ((lists lists))
(match lists
(((heads tails ...) ...)
(let ((tail (loop tails))
(head (defer-to-thread-pool-channel
(lambda ()
(apply proc heads)))))
(cons (fetch-result-of-defered-thunk head) tail)))
(_
'())))))
(define par-map& (par-mapper' map cons))
(define (chunk lst max-length)
(if (> (length lst)
max-length)
(call-with-values (lambda ()
(split-at lst max-length))
(lambda (first-lst rest)
(cons first-lst
(chunk rest max-length))))
(list lst)))
(define (chunk! lst max-length)
(if (> (length lst)
max-length)
(call-with-values (lambda ()
(split-at! lst max-length))
(lambda (first-lst rest)
(cons first-lst
(chunk! rest max-length))))
(list lst)))
(define* (chunk-for-each! proc chunk-size #:rest lsts)
(define (do-one-iteration lsts)
(if (> (length (car lsts))
chunk-size)
(let ((chunks-and-rest
(map (lambda (lst)
(call-with-values (lambda ()
(split-at! lst chunk-size))
(lambda (first-lst rest)
(cons first-lst
rest))))
lsts)))
(apply proc
(map car chunks-and-rest))
(do-one-iteration
(map cdr chunks-and-rest)))
(apply proc lsts)))
(let ((list-lengths (map length lsts)))
(unless (eq? 1 (length (delete-duplicates list-lengths)))
(error "lists not equal length"))
(unless (eq? 0 (first list-lengths))
(do-one-iteration lsts)))
#t)
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