Writer/Reader where a reader has to read 2 times in a row
So I have this problem that is kind of a classic writer/reader problem only with a twist.
Let's say, for example that you have one writer and multiple readers. The writer puts multiple messages in the shared data structure (a message contains of two small messages) so the data structure will look something like this: [m11 m12 m21 m22 m31 m32..] ,
where first number is message number and the second number is the part number. How can i make a reader receive one of the messages without beeing interrupted by another reader?
For example:
If reader 1 takes m11, I want that the shared resource to be blocked until he also reads m12.
The solution must be done only with semaphores or locks and a reader can only read one message at a time.
java c algorithm parallel-processing
asked Nov 15 '18 at 11:23
danieldaniel
63
add a comment |
So I have this problem that is kind of a classic writer/reader problem only with a twist.
Let's say, for example that you have one writer and multiple readers. The writer puts multiple messages in the shared data structure (a message contains of two small messages) so the data structure will look something like this: [m11 m12 m21 m22 m31 m32..] ,
where first number is message number and the second number is the part number. How can i make a reader receive one of the messages without beeing interrupted by another reader?
For example:
If reader 1 takes m11, I want that the shared resource to be blocked until he also reads m12.
The solution must be done only with semaphores or locks and a reader can only read one message at a time.
java c algorithm parallel-processing
asked Nov 15 '18 at 11:23
danieldaniel
63
1
What have you tried so far? What's the issue?
– Mark
Nov 15 '18 at 11:39
What i have tried so far is implementing the classic solution, but only allow one reader at a time. The problem that i am facing is that after a reader gets the first part or the message sometimes a different rather takes the shared resource and takes the second part. I would want that the resource stays blocked untill the first reader also gets the second part.
– daniel
Nov 15 '18 at 11:46
Readers should not read from the data structure you described. Here's what I would imagine: Every 2 messages written, the writer locks a separate data structure and move the pair of messages there, afterwards releasing the lock. Then, when a reader wants to read, it reads both messages at once by locking in order to prevent the writer from writing, releasing the lock after finishing the read.
– luci88filter
Nov 15 '18 at 12:21
I understand your solution. The problem I see is that a reader can t read two messages at once. Imagine that the reader communicates with the data structure with a function that can only return one message at a time. Or maybe I don t understand correctly, how could the reader read 2 messages at the same time with this restriction?
– daniel
Nov 15 '18 at 13:00
I found a solution in java: ReentrantLock
– daniel
Nov 25 '18 at 19:32
add a comment |
So I have this problem that is kind of a classic writer/reader problem only with a twist.
Let's say, for example that you have one writer and multiple readers. The writer puts multiple messages in the shared data structure (a message contains of two small messages) so the data structure will look something like this: [m11 m12 m21 m22 m31 m32..] ,
where first number is message number and the second number is the part number. How can i make a reader receive one of the messages without beeing interrupted by another reader?
For example:
If reader 1 takes m11, I want that the shared resource to be blocked until he also reads m12.
The solution must be done only with semaphores or locks and a reader can only read one message at a time.
java c algorithm parallel-processing
asked Nov 15 '18 at 11:23
danieldaniel
63
So I have this problem that is kind of a classic writer/reader problem only with a twist.
Let's say, for example that you have one writer and multiple readers. The writer puts multiple messages in the shared data structure (a message contains of two small messages) so the data structure will look something like this: [m11 m12 m21 m22 m31 m32..] ,
where first number is message number and the second number is the part number. How can i make a reader receive one of the messages without beeing interrupted by another reader?
For example:
If reader 1 takes m11, I want that the shared resource to be blocked until he also reads m12.
The solution must be done only with semaphores or locks and a reader can only read one message at a time.
java c algorithm parallel-processing
java c algorithm parallel-processing
asked Nov 15 '18 at 11:23
danieldaniel
63
asked Nov 15 '18 at 11:23
danieldaniel
63
edited Nov 15 '18 at 11:33
daniel
asked Nov 15 '18 at 11:23
danieldaniel
63
asked Nov 15 '18 at 11:23
danieldaniel
63
asked Nov 15 '18 at 11:23
danieldaniel
63
63
1
What have you tried so far? What's the issue?
– Mark
Nov 15 '18 at 11:39
What i have tried so far is implementing the classic solution, but only allow one reader at a time. The problem that i am facing is that after a reader gets the first part or the message sometimes a different rather takes the shared resource and takes the second part. I would want that the resource stays blocked untill the first reader also gets the second part.
– daniel
Nov 15 '18 at 11:46
Readers should not read from the data structure you described. Here's what I would imagine: Every 2 messages written, the writer locks a separate data structure and move the pair of messages there, afterwards releasing the lock. Then, when a reader wants to read, it reads both messages at once by locking in order to prevent the writer from writing, releasing the lock after finishing the read.
– luci88filter
Nov 15 '18 at 12:21
I understand your solution. The problem I see is that a reader can t read two messages at once. Imagine that the reader communicates with the data structure with a function that can only return one message at a time. Or maybe I don t understand correctly, how could the reader read 2 messages at the same time with this restriction?
– daniel
Nov 15 '18 at 13:00
I found a solution in java: ReentrantLock
– daniel
Nov 25 '18 at 19:32
add a comment |
1
What have you tried so far? What's the issue?
– Mark
Nov 15 '18 at 11:39
What i have tried so far is implementing the classic solution, but only allow one reader at a time. The problem that i am facing is that after a reader gets the first part or the message sometimes a different rather takes the shared resource and takes the second part. I would want that the resource stays blocked untill the first reader also gets the second part.
– daniel
Nov 15 '18 at 11:46
Readers should not read from the data structure you described. Here's what I would imagine: Every 2 messages written, the writer locks a separate data structure and move the pair of messages there, afterwards releasing the lock. Then, when a reader wants to read, it reads both messages at once by locking in order to prevent the writer from writing, releasing the lock after finishing the read.
– luci88filter
Nov 15 '18 at 12:21
I understand your solution. The problem I see is that a reader can t read two messages at once. Imagine that the reader communicates with the data structure with a function that can only return one message at a time. Or maybe I don t understand correctly, how could the reader read 2 messages at the same time with this restriction?
– daniel
Nov 15 '18 at 13:00
I found a solution in java: ReentrantLock
– daniel
Nov 25 '18 at 19:32
1
1
What have you tried so far? What's the issue?
– Mark
Nov 15 '18 at 11:39
What have you tried so far? What's the issue?
– Mark
Nov 15 '18 at 11:39
What i have tried so far is implementing the classic solution, but only allow one reader at a time. The problem that i am facing is that after a reader gets the first part or the message sometimes a different rather takes the shared resource and takes the second part. I would want that the resource stays blocked untill the first reader also gets the second part.
– daniel
Nov 15 '18 at 11:46
What i have tried so far is implementing the classic solution, but only allow one reader at a time. The problem that i am facing is that after a reader gets the first part or the message sometimes a different rather takes the shared resource and takes the second part. I would want that the resource stays blocked untill the first reader also gets the second part.
– daniel
Nov 15 '18 at 11:46
Readers should not read from the data structure you described. Here's what I would imagine: Every 2 messages written, the writer locks a separate data structure and move the pair of messages there, afterwards releasing the lock. Then, when a reader wants to read, it reads both messages at once by locking in order to prevent the writer from writing, releasing the lock after finishing the read.
– luci88filter
Nov 15 '18 at 12:21
Readers should not read from the data structure you described. Here's what I would imagine: Every 2 messages written, the writer locks a separate data structure and move the pair of messages there, afterwards releasing the lock. Then, when a reader wants to read, it reads both messages at once by locking in order to prevent the writer from writing, releasing the lock after finishing the read.
– luci88filter
Nov 15 '18 at 12:21
I understand your solution. The problem I see is that a reader can t read two messages at once. Imagine that the reader communicates with the data structure with a function that can only return one message at a time. Or maybe I don t understand correctly, how could the reader read 2 messages at the same time with this restriction?
– daniel
Nov 15 '18 at 13:00
I understand your solution. The problem I see is that a reader can t read two messages at once. Imagine that the reader communicates with the data structure with a function that can only return one message at a time. Or maybe I don t understand correctly, how could the reader read 2 messages at the same time with this restriction?
– daniel
Nov 15 '18 at 13:00
I found a solution in java: ReentrantLock
– daniel
Nov 25 '18 at 19:32
I found a solution in java: ReentrantLock
– daniel
Nov 25 '18 at 19:32
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1
What have you tried so far? What's the issue?
– Mark
Nov 15 '18 at 11:39
What i have tried so far is implementing the classic solution, but only allow one reader at a time. The problem that i am facing is that after a reader gets the first part or the message sometimes a different rather takes the shared resource and takes the second part. I would want that the resource stays blocked untill the first reader also gets the second part.
– daniel
Nov 15 '18 at 11:46
Readers should not read from the data structure you described. Here's what I would imagine: Every 2 messages written, the writer locks a separate data structure and move the pair of messages there, afterwards releasing the lock. Then, when a reader wants to read, it reads both messages at once by locking in order to prevent the writer from writing, releasing the lock after finishing the read.
– luci88filter
Nov 15 '18 at 12:21
I understand your solution. The problem I see is that a reader can t read two messages at once. Imagine that the reader communicates with the data structure with a function that can only return one message at a time. Or maybe I don t understand correctly, how could the reader read 2 messages at the same time with this restriction?
– daniel
Nov 15 '18 at 13:00
I found a solution in java: ReentrantLock
– daniel
Nov 25 '18 at 19:32