WO2017096734A1

WO2017096734A1 - Program detection method and device

Info

Publication number: WO2017096734A1
Application number: PCT/CN2016/077653
Authority: WO
Inventors: 巩晓波
Original assignee: 腾讯科技（深圳）有限公司
Priority date: 2015-12-10
Filing date: 2016-03-29
Publication date: 2017-06-15
Also published as: CN105389258A; CN105389258B

Abstract

Embodiments of the present invention provide a program detection method and device. The method may comprise: detecting a first time at which a target message in a message queue of a main thread is executed and a second time at which a message following the target message is executed; determining the execution duration of the target message according to the first time and the second time; and determining that screen stuttering is caused by the execution of the target message if the execution duration is greater than a preset threshold, and outputting the target message. According to the present invention, by measuring execution durations of target messages in a main thread, target messages that cause screen stuttering can be precisely located and outputted.

Description

Program detection method and device

The present application claims priority to Chinese Patent Application No. 201510916597.9, filed on Dec. 10, 2015, the entire disclosure of which is incorporated herein by reference.

Technical field

The present invention relates to the field of communications technologies, and in particular, to a program detection method and a program detection apparatus.

Background technique

Android applications are message driven, including the display of the interface and the execution of the program logic. The interface display is driven in the form of a series of screen refresh messages in the main thread. For example, when the user's finger swipes a list, the system constructs a screen refresh message and throws it into the message queue of the main thread. Only when the message before the message is executed, the message will be executed. When the message is executed, the screen will be executed. The content of the next frame will be displayed. The function logic of the program developer is also queued in the main thread in the form of a message. If a program logic message thrown by the developer blocks the screen refresh message because the execution time is too long, the screen display occurs. In the prior art, it is impossible to accurately locate the message that generates the card.

Summary of the invention

The embodiment of the invention provides a program detection method and device, which can accurately locate and output a target message that causes a screen to be jammed by detecting the execution duration of the target message in the main thread.

In one aspect, the present invention provides a program detection method, which may include:

Detecting a first time when the target message is executed in the message queue of the main thread and a second time of executing the message after the target message;

Determining an execution duration of the target message according to the first time and the second time;

If the execution duration is greater than a preset threshold, determining that execution of the target message causes the screen to jam and output the target message.

In another aspect, the present invention provides a program detecting apparatus, which may include:

a detecting module, configured to detect a first time of execution of a target message in a message queue of the main thread and a second time after the message following the target message is executed;

a determining module, configured to determine an execution duration of the target message according to the first time and the second time;

Determining an output module, if the execution duration is greater than a preset threshold, determining that execution of the target message causes the screen to be stuck and outputting the target message.

Embodiments of the present invention have the following beneficial effects:

In the embodiment of the present invention, the first time of executing the target message in the message queue of the main thread and the second time of executing the message after the target message are determined, and the execution time of the target message is determined according to the first time and the second time, if executed If the duration is greater than the preset threshold, it is determined that the execution of the target message causes the screen to be jammed and the target message is output. This manner can accurately locate the target message that causes the screen to be jammed by detecting the execution duration of the target message in the main thread.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any creative work.

FIG. 1 is a flowchart of a method for detecting a program according to an embodiment of the present invention;

FIG. 2 is a flowchart of another method for detecting a program according to an embodiment of the present invention;

FIG. 3 is a flowchart of still another method for detecting a program according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of performing a screen refresh message according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a program carton according to an embodiment of the present invention; FIG.

FIG. 6 is a schematic diagram of a detection program stuck according to an embodiment of the present invention; FIG.

FIG. 7 is a schematic structural diagram of a program detecting apparatus according to an embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a detection module according to an embodiment of the present disclosure;

FIG. 9 is a schematic structural diagram of another detection module according to an embodiment of the present invention; and

FIG. 10 is a schematic structural diagram of another program detecting apparatus according to an embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

The program detection method provided by the embodiment of the present invention will be described in detail below with reference to FIG.

FIG. 1 is a flowchart of a method for detecting a program according to an embodiment of the present invention; the method may include the following steps S100-S102.

S100. Detect a first time when the target message is executed in the message queue of the main thread and a second time after the message is executed after the target message.

In a specific embodiment, the Android application is message driven, including the display of the interface and the execution of the program logic. The display of the interface is driven in the form of a series of screen refresh messages in the main thread. For example, when the user swipes a list, the system constructs a screen refresh message and throws it into the message queue of the main thread. Only when the message before the screen refresh message is executed, the message will be executed when the screen is refreshed. The screen displays the contents of the next frame when the message is executed. Generally speaking, the frequency of screen refresh is 60fps, which means that each screen refresh message can not be executed for more than 16 milliseconds. If this time is exceeded, the user will feel the card. As shown in FIG. 4, it is a schematic diagram of the main thread of the screen refresh message execution, and the screen refresh message is executed in the main thread at a frequency of 16 milliseconds.

Often some of the functional logic of a program developer is also queued for execution in the main thread in the form of a message, such as a program logic message, if a program logic message thrown by a developer blocks the screen refresh message because its execution time is too long. Carton happened. As shown in FIG. 5, if the execution time of the program logic message exceeds a preset threshold, the execution of the screen refresh message is blocked, and the screen appears to be stuck.

In the actual development process, it is necessary to be able to accurately locate the program logic message that generates the stuck, so that the program logic message can be removed from the main thread for execution. The present invention provides a mechanism for automatically detecting such a message that is too long to execute.

In the main thread, each message is queued and executed in the form of a message queue, and the first time of executing the target message in the main thread message queue and the second execution of the message after the target message are obtained. time. The target message may be a message of the main thread's message queue front end, that is, a message to be executed, and the type of the message may be a program logic message or a screen refresh message.

S101. Determine, according to the first time and the second time, an execution duration of the target message.

In a specific embodiment, the execution time of the target message may be determined according to the first time executed by the target message and the second time after the message execution of the target message, as shown in FIG. 5, according to the first screen refresh message of the main thread. The first time and the second time after the program logic message after the screen refresh message is executed, the execution time of the first screen refresh message can be calculated.

Specifically, the determining the execution duration of the target message according to the first time and the second time includes:

Calculating a duration formed between the first time and the second time, and determining the duration as an execution duration of the target message.

In a specific embodiment, calculating a duration formed between the first time and the second time, optionally, the calculating method may be: subtracting the second time point from the first time point, for example, the first time is 5 ms (relative For the entire program execution time), the second time is 17ms (relative to the entire program execution time), and the duration is 17ms-5ms=12ms, which is the execution time of the target message.

S102. If the execution duration is greater than a preset threshold, determining that execution of the target message causes the screen to be stuck and outputting the target message.

In a specific embodiment, if the execution duration is greater than the preset threshold, the execution time of the target message is too long, which may block the execution of the screen refresh message, thereby causing the screen to be stuck, in order to enable the developer to know which target message is explicitly known. Causes the card to be output, and outputs the target message whose execution time is too long.

FIG. 2 is a flowchart of another method for detecting a program according to an embodiment of the present invention; the method may include the following steps S200-S204.

S200. When detecting that the first detection message is executed, determining an execution time of the first detection message as a first time of execution of a target message in a message queue of the main thread.

In a specific embodiment, in order to be able to detect the first time of executing the target message and the second time of executing the message after the target message, as shown in FIG. 6, the present invention starts a detection thread for monitoring when the program is started. The main thread's message is executed. The implementation method may be to continuously send a detection message to the message queue front end of the main thread.

As shown in FIG. 6, when the refresh message of the main thread is being executed, the first detection message "0" is set in the front end of the message queue of the main thread, and when the first detection message "0" is executed, the first detection message is 0. The execution time is determined as the first time the target message (ie, the program logic message) in the message queue of the main thread executes.

S201. Dequeue the target message, and continue to set a second detection message on a front end of the message queue of the main thread.

In a specific embodiment, the execution time of the first detection message is very short, almost at the microsecond level. When the first detection message is executed, the target message (ie, the program logic message) is dequeued and executed in the message queue of the main thread. The front end continues to set the second detection message "1".

S202. When performing the second detection message, determining an execution time of the second detection message as a second time of execution of the message after the target message.

In a specific embodiment, when the second detection message "1" is executed, the execution time of the second detection message "1" is determined as a message after the target message (ie, a program logic message) (ie, a screen refresh message). The second time of execution. Because when the second detection message "1" is executed, it indicates that the program logic message is just finished.

The execution time of the target message (that is, the program logic message) may be determined according to the first time and the second time, and the execution time is less than the preset threshold, and the message after the target message is dequeued, and the message is sent to the front end of the main thread message queue. The next detection message, the execution time is greater than the preset threshold, indicating that the target message being executed in the main thread is too time consuming, which may cause the interface to be stuck. At this time, the present invention outputs the query information for locating the target message, and queries according to the query information. Target information and output the target message,

S203. Determine, according to the first time and the second time, an execution duration of the target message.

S204. If the execution duration is greater than a preset threshold, determining that execution of the target message causes the screen to be stuck and outputting the target message.

For the steps S203-S204 of the embodiment of the present invention, refer to the steps S101-S102 of the embodiment of FIG. 1 , and details are not described herein again.

Please refer to FIG. 3, which is a flowchart of still another method for detecting a program according to an embodiment of the present invention; the method may include the following steps S300-S304.

S300, registering a callback notification on a message execution function of the main thread of the system.

In a specific embodiment, in order to be able to monitor the execution time of each function in the main thread, a callback notification is registered on the message execution function of the main thread of the system.

S301. Acquire a first callback notification of the system when the target message in the message queue of the main thread is executed, where the first callback notification carries the first time when the target message is executed.

In a specific embodiment, when the system executes the target message in the message queue of the main thread, the first callback notification may be returned, where the first callback notification carries the first time when the target message is executed.

S302. Acquire a second callback notification of the system when the message after the target message is executed, where the second callback notification carries a second time point of execution of the message after the target message.

In a specific embodiment, when the system executes the message after the target message in the message queue of the main thread, the second callback notification may also be returned, where the second callback notification carries the second time of execution of the message after the target message.

S303. Determine, according to the first time and the second time, an execution duration of the target message.

S304. If the execution duration is greater than a preset threshold, determining that execution of the target message causes the screen to be stuck and outputting the target message.

For the steps S303-S304 of the embodiment of the present invention, refer to the steps S101-S102 of the embodiment of FIG. 1 , and details are not described herein again.

A program detecting apparatus according to an embodiment of the present invention will be described in detail below with reference to FIG. 7 to FIG.

FIG. 7 is a schematic structural diagram of a program detecting apparatus according to an embodiment of the present invention; the apparatus may include: a detecting module 100, a determining module 101, and a determining output module 102;

The detecting module 100 is configured to detect a first time when the target message is executed in the message queue of the main thread and a second time when the message after the target message is executed;

In the main thread, each message is queued and executed in the form of a message queue, and the first time when the target message in the main thread message queue is executed and the second time after the target message is executed are acquired. The target message may be a message of the main thread's message queue front end, that is, a message to be executed, and the type of the message may be a program logic message or a screen refresh message.

The detection module 100 can have the following two alternative implementations:

In a first optional implementation manner, as shown in FIG. 8, the detecting module 100 includes a first determining list. a unit 1000, a setting unit 1001 and a second determining unit 1002;

The first determining unit 1000 is configured to determine, when the first detection message is executed, an execution time of the first detection message as a first time when the target message in the message queue of the main thread is executed;

As shown in FIG. 6, when the refresh message of the main thread is being executed, the first detection message “0” is set in the front end of the message queue of the main thread, and when the first detection message “0” is executed, the first determining unit 1000 The execution time of a detection message "0" is determined as the first time the target message (ie, the program logic message) in the message queue of the main thread is executed.

a setting unit 1001, configured to dequeue the target message, and continue to set a second detection message at a front end of the message queue of the main thread;

In a specific embodiment, the execution time of the first detection message is very short, almost at the microsecond level. When the first detection message is executed, the target message (ie, the program logic message) is dequeued, and the setting unit 1001 is simultaneously in the main thread. The front end of the message queue continues to set the second detection message "1".

The second determining unit 1002 is configured to determine, when the second detection message is executed, an execution time of the second detection message as a second time of execution of the message after the target message.

In a specific embodiment, when the second detection message "1" is executed, the second determining unit 1002 determines the execution time of the second detection message "1" as the message after the target message (ie, the program logic message) (ie, Is the screen refresh message) the second time of execution. Because when the second detection message "1" is executed, it indicates that the program logic message is just finished.

The execution time of the target message (that is, the program logic message) may be determined according to the first time and the second time, and the execution time is less than the preset threshold, and the message after the target message is dequeued, and the message is sent to the front end of the main thread message queue. The next detection message, the execution time is greater than the preset threshold, indicating that the target message being executed in the main thread is too time consuming, may cause the interface to be stuck, output query information for locating the target message, and query the target information according to the query information, and The target message is output to facilitate the developer to locate the source of the card.

In a second optional implementation manner, the device further includes a registration module, and the detection module 100 may include a first obtaining unit 1003 and a second obtaining unit 1004;

a registration module, configured to register a callback notification on a message execution function of the main thread of the system;

The first obtaining unit 1003 is configured to acquire a first callback notification of the system when the target message in the message queue of the main thread is executed, where the first callback notification carries the first time when the target message is executed;

In a specific embodiment, when the system performs the target message in the message queue of the main thread, the first callback notification may be returned, and the first obtaining unit 1003 acquires a first callback notification of the system, where the first callback notification carries the target message. The first time.

The second obtaining unit 1004 is configured to acquire a second callback notification of the system when the message after the target message is executed, where the second callback notification carries a second time point of execution of the message after the target message.

The determining module 101 is configured to determine an execution duration of the target message according to the first time and the second time;

In a specific embodiment, the determining module 101 determines the execution time of the target message according to the first time executed by the target message and the second time after the message execution of the target message, as shown in FIG. 5, according to the first screen of the main thread. The execution time of the first screen refresh message can be calculated by refreshing the first time of execution of the message and the second time of execution of the program logic message after the screen refresh message.

Optionally, the determining module 101 is specifically configured to calculate a duration formed between the first time and the second time, and determine the duration as an execution duration of the target message.

Determining the output module 102, if the execution duration is greater than a preset threshold, determining that execution of the target message causes the screen to be stuck, and outputting the target message.

In a specific embodiment, if the execution duration is greater than the preset threshold, the execution time of the target message is too long, which may block the execution of the screen refresh message, thereby causing the screen to be stuck, in order to enable the developer to know which target message is explicitly known. As a result of the stuck, it is determined that the output module 102 outputs the target message whose execution time is too long.

According to an embodiment of the present invention, the program detecting method according to FIGS. 1 to 3 may be performed by each unit in the program detecting device shown in FIGS. 7 to 9. For example, steps S100, S101, and S102 shown in FIG. 1 may be performed by the detection module 100, the determination module 101, and the determination output module 102 shown in FIG. 7, respectively. Steps S200, S201, S202, S203, and S204 shown in FIG. 2 may be respectively performed by the first determining unit 1000, the setting unit 1001, the second determining unit 1002, the determining module 101, and the determination output shown in FIGS. 7 and 8. Module 102 is executed. Steps S300, S301, S302, S303, and S304 shown in FIG. 3 may be respectively performed by the registration module (not shown) shown in FIG. 7 and FIG. 9, the first acquisition unit 1003, the second acquisition unit 1004, and the determination module. 101 and determining the output module 102 to execute.

According to another embodiment of the present invention, each unit in the program detecting apparatus shown in FIGS. 7 to 9 may be separately or entirely combined into one or several other units, or one of the units may also be It is further divided into a plurality of functionally smaller units, which can achieve the same operation without affecting the realization of the technical effects of the embodiments of the present invention. The above units are divided based on logical functions. In practical applications, the functions of one unit may also be implemented by multiple units, or the functions of multiple units may be implemented by one unit. In other embodiments of the invention, the terminal device may also include other modules. However, in practical applications, these functions can also be implemented by other units, and can be implemented by multiple units.

According to another embodiment of the present invention, it is possible to operate on a general-purpose computing device such as a computer including a processing unit and a storage element including a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and the like. A computer program (including program code) for performing the program detecting method as shown in FIGS. 1 to 3 to construct a program detecting device as shown in FIGS. 7 to 9, and a program detecting method according to an embodiment of the present invention . The computer program can be recorded, for example, on a computer readable recording medium, and loaded in the above computing device by a computer readable recording medium, and Run in it.

Referring to FIG. 10, FIG. 10 is a schematic structural diagram of another program detecting apparatus according to an embodiment of the present invention. As shown in FIG. 10, the program detecting means may include at least one processor 1101, such as a CPU, at least one communication bus 1102, a user interface 1103, at least one network interface 1104, and a memory 1105. The communication bus 1102 is used to implement connection communication between these components. The user interface 1103 can include a display and a keyboard. The optional user interface 1103 can also include a standard wired interface and a wireless interface. The network interface 1104 can optionally include a standard wired interface, a wireless interface (such as a WI-FI interface, a Bluetooth interface). The memory 1105 may be a high speed RAM memory or a non-volatile memory such as at least one disk memory. The memory 1105 can also optionally be at least one storage device located away from the processor 1101. The memory 1105 as a computer storage medium may further include an operating system, a network communication module, a user interface module, and a data processing application.

In the data processing apparatus shown in FIG. 10, when the above apparatus is a user terminal, the network interface 1104 is mainly used to connect to a server and perform data communication with the server. The memory 1105 stores a set of program codes, and the processor 1101 calls the program code stored in the memory 1105 to perform the following operations:

Determining, according to the first time and the second time, an execution duration of the target message; and

In an optional embodiment, the processor 1101 invokes a program code stored in the memory 1105 to determine an execution duration of the target message according to the first time and the second time, Can include:

In an alternate embodiment, processor 1101 invokes program code stored in memory 1105 for performing the following operations:

Determining, when the first detection message is executed, an execution time of the first detection message as a first time of execution of a target message in a message queue of the main thread;

Dequeuing the target message, and continuing to set a second detection message at a front end of the message queue of the main thread;

Determining, when the second detection message is executed, an execution time of the second detection message as a second time of execution of the message after the target message;

Registering a callback notification on a message execution function of the main thread of the system;

Obtaining a first callback notification of the system when the target message in the message queue of the main thread is executed, where the first callback notification carries the first time when the target message is executed;

Obtaining a second callback notification of the system when the message following the target message is executed, where the second callback notification carries a second time point of execution of the message after the target message;

A person skilled in the art can understand that all or part of the process of implementing the above embodiment method can be completed by computer program related hardware, and the program can be stored in a computer readable storage medium, FIG. 7 - a program corresponding to the module of the program detecting means shown in FIG. 9 can be stored in a readable storage medium of the program detecting means and executed by at least one of the program detecting means to implement the above-described program detecting method, the method Including the method embodiments of FIG. 1 to FIG. Process.

The logic and/or steps represented in the flowchart or otherwise described herein, for example, may be considered as an ordered list of executable instructions for implementing logical functions, and may be embodied in any computer readable medium, Used in conjunction with, or in conjunction with, an instruction execution system, apparatus, or device (eg, a computer-based system, a system including a processor, or other system that can fetch instructions and execute instructions from an instruction execution system, apparatus, or device) Or use with equipment. For the purposes of this specification, a "computer-readable medium" can be any apparatus that can contain, store, communicate, propagate, or transport a program for use in an instruction execution system, apparatus, or device, or in conjunction with the instruction execution system, apparatus, or device. More specific examples (non-exhaustive list) of computer readable media include the following: electrical connections (electronic devices) having one or more wires, portable computer disk cartridges (magnetic devices), random access memory (RAM), Read only memory (ROM), erasable editable read only memory (EPROM or flash memory), fiber optic devices, and portable compact disk read only memory (CDROM). In addition, the computer readable medium may even be a paper or other suitable medium on which the program can be printed, as it may be optically scanned, for example by paper or other medium, followed by editing, interpretation or, if appropriate, other suitable The method is processed to obtain the program electronically and then stored in computer memory.

It should be understood that portions of the invention may be implemented in hardware, software, firmware or a combination thereof. In the above-described embodiments, multiple steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or combination of the following techniques well known in the art: having logic gates for implementing logic functions on data signals. Discrete logic circuits, application specific integrated circuits with suitable combinational logic gates, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

The above mentioned storage medium may be a read only memory, a magnetic disk or an optical disk or the like. Although the embodiments of the present invention have been shown and described, it is understood that the above-described embodiments are illustrative and are not to be construed as limiting the scope of the invention. The embodiments are subject to variations, modifications, substitutions and variations.

Claims

A program detection method, comprising:

Detecting a first time when the target message is executed in the message queue of the main thread and a second time of executing the message after the target message;

Determining an execution duration of the target message according to the first time and the second time;

If the execution duration is greater than a preset threshold, determining that execution of the target message causes the screen to jam and output the target message.
The program detection method according to claim 1, wherein the message queue of the main thread includes at least one message, and each of the at least one message is of a program logic message or a screen refresh message.
The program detection method according to claim 2, wherein the determining the execution duration of the target message according to the first time and the second time comprises:

Calculating a duration formed between the first time and the second time, and determining the duration as an execution duration of the target message.
The program detection method according to claim 1, wherein the message queue front end of the main thread sets a first detection message, and the first detection message is before the target message;

The detecting the first time of execution of the target message in the message queue of the main thread and the second time of executing the message after the target message include:

Determining, when the first detection message is executed, an execution time of the first detection message as a first time of execution of a target message in a message queue of the main thread;

Dequeuing the target message, and continuing to set a second detection message at a front end of the message queue of the main thread;

When the second detection message is executed, the execution time of the second detection message is determined to be the second time when the message following the target message is executed.
The program detecting method according to any one of claims 1 to 4, wherein the detecting the first time in which the target message is executed in the message queue of the main thread and the second execution of the message following the target message Before time, it also includes:

Registering a callback notification on a message execution function of the main thread of the system;

The detecting the first time of execution of the target message in the message queue of the main thread and the second time of executing the message after the target message include:

Obtaining a first callback notification of the system when the target message in the message queue of the main thread is executed, where the first callback notification carries the first time when the target message is executed;

And when the message following the target message is executed, acquiring a second callback notification of the system, where the second callback notification carries a second time point of execution of the message after the target message.
A program detecting device, comprising:

a detecting module, configured to detect a first time when the target message is executed in the message queue of the main thread and a second time after the message is executed after the target message;

a determining module, configured to determine an execution duration of the target message according to the first time and the second time;

Determining an output module, if the execution duration is greater than a preset threshold, determining that execution of the target message causes the screen to be stuck and outputting the target message.
The program detecting apparatus according to claim 6, wherein the message queue of the main thread includes at least one message, and each of the at least one message is of a program logic message or a screen refresh message.
The program detecting apparatus according to claim 7, wherein the determining module is specifically configured to calculate a duration formed between the first time and the second time, and determine the duration as the The execution time of the target message.
The program detecting apparatus according to claim 6, wherein the message queue front end of the main thread sets a first detection message, the first detection message is before the target message; The test module includes:

a first determining unit, configured to determine, when the first detection message is executed, an execution time of the first detection message as a first time of execution of a target message in a message queue of the main thread;

a setting unit, configured to dequeue the target message, and continue to set a second detection message at a front end of the message queue of the main thread;

And a second determining unit, configured to determine, when the second detection message is executed, an execution time of the second detection message as a second time of execution of the message after the target message.
The program detecting device according to any one of claims 6 to 9, wherein the device further comprises:

a registration module, configured to register a callback notification on a message execution function of the main thread of the system;

The detection module includes:

a first acquiring unit, configured to acquire a first callback notification of the system when the target message in the message queue of the main thread is executed, where the first callback notification carries the first time when the target message is executed;

And a second acquiring unit, configured to acquire a second callback notification of the system when the message after the target message is executed, where the second callback notification carries a second time point of execution of the message after the target message.