locking

损失函数优化器总结

一世执手 提交于 2020-02-28 00:54:28
# adadelta optimizer = tf.train.AdadeltaOptimizer(learning_rate=0.001, rho=0.95, epsilon=1e-8, use_locking=False, name="Adadelta") # adagrad optimizer = tf.train.AdagradOptimizer(learning_rate=0.001, initial_accumulator_value=0.1, use_locking=False, name="Adagrad") # adam optimizer = tf.train.AdamOptimizer(learning_rate=0.001, beta1=0.9, beta2=0.999, epsilon=1e-8, use_locking=False, name="Adam") # ftrl optimizer = tf.train.FtrlOptimizer(learning_rate=0.001, learning_rate_power=-0.5, initial_accumulator_value=0.1, l1_regularization_strength=0.0, l2_regularization_strength=0.0, use_locking=False

Why is notify required inside a critical section?

时光毁灭记忆、已成空白 提交于 2020-02-25 04:10:44
问题 I'm reading this book here (official link, it's free) to understand threads and parallel programming. Here's the question. Why does the book say that pthread_cond_signal must be done with a lock held to prevent data race? I wasn't sure, so I referred to this question (and this question too), which basically said "no, it's not required". Why would a race condition occur? What and where is the race condition being described? The code and passage in question is as follows. ... The code to wake a

Why is notify required inside a critical section?

假如想象 提交于 2020-02-25 04:10:31
问题 I'm reading this book here (official link, it's free) to understand threads and parallel programming. Here's the question. Why does the book say that pthread_cond_signal must be done with a lock held to prevent data race? I wasn't sure, so I referred to this question (and this question too), which basically said "no, it's not required". Why would a race condition occur? What and where is the race condition being described? The code and passage in question is as follows. ... The code to wake a

Does SQL Server acquire locks even without an explicit transaction?

拟墨画扇 提交于 2020-02-24 09:22:11
问题 I was reading about MSSQL Locking for the first time, and it many places, the locking mechanism concepts depend on the existence of Transactions. I was wondering whether locking (in general) is possible without having any Transactions involved? 回答1: When no explicit transaction exists, each SQL statement is executed in an automatic (autocommit) transaction. Normal locking behavior will apply in that case and the locks released when the automatic transaction is completed as the statement

Script stuck on exit when using atexit to terminate threads

江枫思渺然 提交于 2020-02-23 04:46:06
问题 I'm playing around with threads on python 3.7.4, and I want to use atexit to register a cleanup function that will (cleanly) terminate the threads. For example: # example.py import threading import queue import atexit import sys Terminate = object() class Worker(threading.Thread): def __init__(self): super().__init__() self.queue = queue.Queue() def send_message(self, m): self.queue.put_nowait(m) def run(self): while True: m = self.queue.get() if m is Terminate: break else: print("Received

when/what locks are hold/released in READ COMMITTED isolation level

主宰稳场 提交于 2020-02-17 23:03:34
问题 I am trying to understand isolation/locks in SQL Server. I have following scenario in READ COMMITTED isolation level(Default) We have a table. create table Transactions(Tid int,amt int) with some records insert into Transactions values(1, 100) insert into Transactions values(2, -50) insert into Transactions values(3, 100) insert into Transactions values(4, -100) insert into Transactions values(5, 200) Now from msdn i understood When a select is fired shared lock is taken so no other

when/what locks are hold/released in READ COMMITTED isolation level

末鹿安然 提交于 2020-02-17 22:56:29
问题 I am trying to understand isolation/locks in SQL Server. I have following scenario in READ COMMITTED isolation level(Default) We have a table. create table Transactions(Tid int,amt int) with some records insert into Transactions values(1, 100) insert into Transactions values(2, -50) insert into Transactions values(3, 100) insert into Transactions values(4, -100) insert into Transactions values(5, 200) Now from msdn i understood When a select is fired shared lock is taken so no other

When does locking or mvcc occur? Where do I need to specify which one the database should use?

怎甘沉沦 提交于 2020-02-10 18:08:32
MVCC applies to isolation levels read-committed and repeatable read (default). You don't need to specify anything for both of these features to work together. Row Level Locking Locking is for when multiple writers are trying to update the same rows. Only one writer can update a row at a time , and the first one to update the row locks it until they commit the change. Other writers have to wait until the first writer commits. But at least with row-level locking, they only have contention if they're updating the same row. A read lock can be used to prevent other users from reading a record (or

How to lock file in PHP?

走远了吗. 提交于 2020-02-06 08:24:12
问题 I'm trying to create a PHP file, which wouldn't run if it's already running. Here's the code I'm using: <?php class Test { private $tmpfile; public function action_run() { $this->die_if_running(); $this->run(); } private function die_if_running() { $this->tmpfile = @fopen('.refresher2.pid', "w"); $locked = @flock($this->tmpfile, LOCK_EX|LOCK_NB); if (! $locked) { @fclose($this->tmpfile); die("Running 2"); } } private function run() { echo "NOT RUNNNING"; sleep(100); } } $test = new Test();

How to lock file in PHP?

*爱你&永不变心* 提交于 2020-02-06 08:24:05
问题 I'm trying to create a PHP file, which wouldn't run if it's already running. Here's the code I'm using: <?php class Test { private $tmpfile; public function action_run() { $this->die_if_running(); $this->run(); } private function die_if_running() { $this->tmpfile = @fopen('.refresher2.pid', "w"); $locked = @flock($this->tmpfile, LOCK_EX|LOCK_NB); if (! $locked) { @fclose($this->tmpfile); die("Running 2"); } } private function run() { echo "NOT RUNNNING"; sleep(100); } } $test = new Test();