JP3042415B2 - Cache memory device and cache control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a cache memory device and a cache control method which can be efficiently used in a mobile computer, a vehicle navigation device, and the like.

[0002]

2. Description of the Related Art Conventionally, a vehicular navigation device has been used to assist a vehicle traveling on an unfamiliar land. The basic function of the vehicle navigation device is to detect the current position of the vehicle and to display the detected current position along with a road map on a display device, but recently, a gas station near a running area,
There is provided a device capable of displaying facility information such as a restaurant or a convenience store, and road information such as traffic congestion on a road at a travel destination. These features are:
For example, this is realized by a configuration in which necessary information is radiated from beacons arranged at key points on the road, and the information is received by a receiver connected to the vehicle navigation device.

[0003] In addition, necessary information can be obtained from a center station by an automobile telephone. Such devices are:
For example, it is disclosed in JP-A-4-261576. In this device, based on the current position of the vehicle, a center station that shares the current position is automatically dialed, and necessary information such as a nearby road map and traffic information is automatically acquired. Has become.

[0004]

In recent years, this is called mobile computing or the like, and a mobile telephone and a computer are connected to each other to exchange information with an information center even when the mobile phone or the like is moving. The technology for doing so is developing. Therefore, it is conceivable to obtain map data and the above-described information accompanying the map data as needed by communication using a mobile phone, and use this information in the vehicle navigation device.

[0005] In this case, the information received from the information center is generally temporarily stored in a cache memory. That is, when the same information is required many times, the information is read from the cache memory and used, and communication with the information center is performed only when new information not stored in the cache memory is required. As a result, the total communication time can be reduced, so that call charges can be saved and the processing speed can be improved.

However, the size of a cache memory is limited, and information cannot be stored beyond that size. Therefore, the cache memory becomes full,
When it is necessary to receive new information, it is necessary to delete a part of the old information in the cache memory. For a method of determining which data block is deleted from the data blocks in the cache memory, see, for example, “Computer Architecture” (written by Hennessy and Patterson, Shinji Tomita, Kazuaki Murakami, and Nikkei B).
(Company P) on pages 412-413. That is, the random method or LRU (Least-Recent
Generally, data is exchanged using the ly Used method. In the random method, a data block selected at random is deleted as a data block to be replaced. On the other hand, in the LRU method, the least recently used block is replaced with the data to be replaced by utilizing the possibility that the referenced block is likely to be referenced again (temporal locality of reference). Selected as a block.

However, in a moving computer system such as a vehicular navigation system, the use order of information is often predictable. There is also a possibility that the cache memory can be used effectively. Therefore, an object of the present invention is to provide a cache memory device that can function more effectively than before.

Another object of the present invention is to provide a cache control method capable of using a cache memory more effectively than the conventional method.

[0009]

According to a first aspect of the present invention, there is provided a storage unit for temporarily storing information, and determination basic information determined based on a property of the information. A determination basic information storage unit that stores information for each piece of information stored in the storage unit, a measurement unit that measures a physical quantity corresponding to the determination basic information, and a measurement result obtained by the measurement unit that is stored in the determination basic information storage unit. Comparing means for comparing the basic information with the determined basic information, and, based on a result of the comparison by the comparing means, an object to be replaced with information to be newly stored in the storage means among the information stored in the storage means. only it contains and means for determining the information should be,
The basic judgment information is the information stored in the storage means.
The corresponding position information, and the measuring means
The current position corresponding to the use point of the information stored in the column is calculated.
Measuring means for measuring the current position,
The current position measured by the current position measuring means and the above
Including means for comparing position information, which is basic information for judgment
A cache memory device characterized in that:

According to a fifth aspect of the present invention, there is provided a cache control method corresponding to the first aspect of the present invention, wherein the step of temporarily storing information in the storage means and the property of the information stored in the storage means are performed. The basic judgment information determined based on
Storing in the determination basic information storage means for each piece of information stored in the storage means, measuring the physical quantity corresponding to the determination basic information, comparing the measured physical quantity with the determination basic information, Deciding information to be replaced with information to be newly stored in the storage means, out of the information stored in the storage means.
In addition, the basic determination information is information stored in the storage means.
Location information that corresponds to the
The information stored in the storage means is used for the physical quantity
The cache control method is characterized in that the current position is a current position corresponding to a point to be executed .

According to these inventions, the information is stored in the storage means, and the basic judgment information determined based on the nature of the information is stored in the basic judgment information storage means. Then, a physical quantity corresponding to the basic judgment information is measured, and the measured physical quantity is compared with the basic judgment information stored in the basic judgment information storage means. Based on the comparison result, information to be replaced with new information is determined from the information stored in the storage unit.

Thus, the information to be replaced is determined based on the measurement result of the physical quantity corresponding to the property of the information, so that unnecessary information can be more reliably replaced. As a result, the storage area of the storage unit can be effectively used, and the possibility that necessary information is deleted can be reduced. A cache memory device that is more effective than employing the technique is realized.

[0013]

[0014]

For example, when the cache memory device of the present invention is used by being mounted on a moving body such as a vehicle, the information stored in the storage means may depend on the position of the moving body. In such a case, the position information is stored as the determination basic information, the current position corresponding to the use point of the information is measured, and the measured current position is compared with the determination basic information, and based on the comparison result, If the information to be replaced is determined in this way, information that is unlikely to be used in the future can be preferentially replaced. Thereby, the storage means can be used efficiently.

According to a second aspect of the present invention, the measuring means includes:
Comprising the further traveling direction predicting means for predicting the traveling direction of the use point information stored in said storage means, said comparing means, the current position measured by said current position measuring means, the determination basic information when comparing the certain location information, a cache memory apparatus according to claim 1, characterized in that the consideration of the traveling direction is predicted by the traveling direction predicting unit.

According to a sixth aspect of the present invention, there is provided a cache control method corresponding to the second aspect of the present invention, wherein the physical quantity corresponding to the basic determination information further includes a traveling direction of a current position. 6. The cache control method according to claim 5 , wherein in the step of determining the information to be replaced, the current position and the traveling direction are compared with the position information as the determination basic information.

According to the present invention, the traveling direction of the information use point is further predicted. Thus, for example, the information corresponding to the position going from now on is left in the storage means, and the information corresponding to the position that has passed is preferentially replaced, so that unnecessary information can be reliably replaced. It can be. According to a third aspect of the present invention, the storage means for temporarily storing information and the nature of the information
The determination basic information determined based on the
Determination basic information storage means for storing for each stored information;
Measuring means for measuring a physical quantity corresponding to the determination basic information
And the result of measurement by the measuring means
Comparison with basic judgment information stored in storage means
Based on the comparison result by the comparing means
Out of the information stored in the storage means,
Should be replaced with new information to be stored in the column
Means for determining information, wherein the determination basic information is effective range information representing an effective area range of the information stored in the storage means, and the measuring means uses information stored in the storage means. Current position measuring means for measuring a current position corresponding to a point, wherein the comparing means determines that the current position measured by the current position measuring means is within an effective area range corresponding to the effective range information which is the determination basic information. it is to Ruki catcher Tsu <br/> Shumemori device and characterized in that for determining whether a.

[0019] The invention of claim 7 is an invention of the cache control method corresponding to the invention of claim 3, temporarily storing means
Storing information in the storage means;
Basic information determined based on the nature of the information
Determination basic information storage for each information stored in the storage means
A step corresponding to the step of storing in the means and the basic information for determination
Measuring the physical quantity, the measured physical quantity and
The information stored in the storage means is compared with the basic information.
Information that should be newly stored in the storage means.
Determining the information to be replaced.
In addition, the determination basic information is effective range information indicating an effective area range of the information stored in the storage unit, and the information stored in the storage unit is used as the physical quantity corresponding to the determination basic information. In the step of determining the information that is the current position corresponding to the point and to be replaced, the information of the replacement target is determined based on whether the current position is within the effective area represented by the effective range information. a feature and be Ruki Yasshu control method that but determined.

In the present invention, the effective range information is used as the basic judgment information. For example, in a computer system used in a moving object, information related to the current position of the moving object may be obtained and written to the storage unit. However, the importance of such information decreases with the movement of the moving object, and finally, the possibility that the information is needed is extremely low. Therefore, if the effective range information is compared with the current position corresponding to the use point of the information, and the information to be replaced is determined based on the comparison result, only the information that is likely to be needed is stored in the storage unit. Can be left.

According to the invention of claim 4 , information is temporarily recorded.
Storage means to remember, and a format determined based on the nature of the information.
Basic information is recorded for each information stored in the storage means.
Storage means for storing the basic judgment information to be remembered;
Measuring means for measuring the corresponding physical quantity;
The measurement result is stored in the determination basic information storage means.
Comparison means for comparing against the basic information
Based on the result of comparison by the comparing means, the information is stored in the storage means.
Of the stored information, it should be newly stored in the storage means
Means for determining information to be replaced with information;
And the determination basic information is valid time information indicating a valid time of information stored in the storage means, and the measuring means sets a current time corresponding to a use time of the information stored in the storage means. The current time measuring means includes a current time measuring means for measuring, and the comparing means determines whether or not the current time measured by the current time measuring means is within a valid time corresponding to the valid time information which is the basic determination information. it is to Ruki Yasshumemori device and characterized in that.

[0022] The invention of claim 8 is the invention of the cache control method corresponding to the invention of claim 4, temporary storage means
Storing information in the storage means;
Basic information determined based on the nature of the information
Determination basic information storage for each information stored in the storage means
A step corresponding to the step of storing in the means and the basic information for determination
Measuring the physical quantity, the measured physical quantity and
The information stored in the storage means is compared with the basic information.
Information that should be newly stored in the storage means.
Determining the information to be replaced.
Seen, the determination information is valid time information indicating the effective time of the information stored in the storage means, the physical quantity corresponding to the determination basic information corresponds to the time information stored in said memory means is utilized In the step of determining the information to be replaced, the information to be replaced is determined based on whether the current time is within the valid time range represented by the valid time information. a Ruki Yasshu control method to <br/> characterized.

In the present invention, the effective time is used as basic information for determination. That is, there is a case where some of the information stored in the storage means is highly likely to be needed in a certain time range, but extremely unlikely to be needed in other times. Therefore, if the current time is measured, it is determined whether or not the current time is within the valid time, and information to be replaced is determined based on the determination result. It can be a replacement target.

[0024]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a basic configuration of a vehicle navigation device to which an embodiment of the present invention is applied. The in-vehicle device 100 mounted on the vehicle has an angular velocity sensor 1, a vehicle speed sensor 2, and a traveling direction and a traveling distance of the vehicle are obtained by integrating outputs of these sensors, respectively. And a position detecting unit 3 for calculating coordinates. The position detector 3 further includes G
A GPS receiver 4 that receives a radio wave from a PS (Global Positioning System) satellite and outputs current position information is connected. The position detection unit 3 is configured to appropriately correct the current position obtained based on the outputs of the angular velocity sensor 1 and the vehicle speed sensor 2 with the position information provided from the GPS receiver 4 to detect an accurate current position. ing.

The current position information detected by the position detector 3 is input to a controller 5 having a microcomputer. The control unit 5 has a CD storing road map data.
A CD-ROM drive 7 in which a ROM 6 can be loaded, a display unit 8 such as a liquid crystal display panel or a CRT for displaying information such as a road map, and a remote controller for performing operations such as selection of display information. 9 are connected. The control unit 5 includes a clock 10 for measuring the current time, a ROM 11 in which a control program is stored, and a RAM 15 in which a cache memory area C is set.

A mobile phone 20 can be connected to the control unit 5. By using the mobile phone 20, the in-vehicle device 100 can perform information communication with the information center 30 via the base station 25 and the network 27. With the above configuration, the control unit 5 acquires the road map data corresponding to the current position given from the position detection unit 3 from the CD-ROM 6, and displays an image in which a predetermined mark is superimposed on the road map on the display unit 8. Display. This allows the user to know the current position of the vehicle.

The control unit 5 controls the mobile phone 20 to make a call to the information center 30 and obtains various information from the information center 30 via the mobile phone 20. The information acquired from the information center 30 includes, for example, a detailed map near the point where the vehicle is traveling, facilities near the current position of the vehicle (gas station, convenience store, etc.), a lunch menu of a restaurant near the current position, There are road congestion information, weather forecast information, interchange guidance information, and the like.

The control unit 5 temporarily stores the information received from the information center 30 in the cache memory area C of the RAM 15. When there is information to be acquired from the information center 30, the control unit 5 first
And if necessary information is read from the cache memory area C. On the other hand, when the necessary information does not exist in the cache memory area C, the control unit 5 sends the information to the information center 3
Get information from 0.

As a result, when there is necessary information in the cache memory area C, there is no need to communicate with the information center 30, so that the processing can be completed in a very short time. Further, since the total communication time with the information center 30 is shortened, the call charge can be saved. Cache memory area C
Is full of received information, it becomes necessary to delete old information and store new information. That is, it is necessary to replace information. In order to determine the information to be replaced, in this embodiment, the following measures are taken.

First, of the information transmitted by the information center 30, information that depends on the position (position-dependent information) is accompanied by position information as tag information. For example, it is assumed that there is information A depending on a certain point P0 as shown in FIG. In this case, the information A is the position-dependent information, and the information indicating the position of the point P0 is the position information. If there is a point P0 on the traveling route of the vehicle, the frequency of accessing the information A is large until the vehicle reaches the point P0, and the frequency of accessing the information A is remarkable when the vehicle passes the point P0. It is considered that the decrease is common.

Therefore, if the information in the cache memory area C is to be replaced when the vehicle is in front of the point P0, the cache hit rate decreases. On the other hand, even if the information A has been accessed recently, if the vehicle has passed the point P0, there is a low possibility that the information A will be accessed in the future. In this case, the information A is replaced. By targeting, the efficiency of the cache is improved.

Therefore, the control unit 5 obtains information on the current position of the vehicle and the traveling direction of the vehicle from the position detection unit 3, and replaces the position-dependent information with reference to the position information which is the tag information. The priority of the object is given. That is, if the vehicle has not reached the position represented by the position information, a low priority is given to the position-dependent information. When the vehicle has passed the position represented by the position information, the position-dependent information is given a high priority, and the position-dependent information is preferentially replaced.

As the position-dependent information, guide information of an interchange can be exemplified. That is, if the information of the interchange is taken into the cache memory area C while the vehicle is traveling on the highway, the probability that the information is used again after the interchange becomes very low. In this case, based on the position information attached to the guide information of the interchange, the control unit 5 preferentially replaces the guide information at the time of passing the interchange.

In the information transmitted from the information center 30, information having a limited effective area range is accompanied by effective range information as tag information. For example, weather forecast information is effective in a wide area range, while road condition information indicating traffic congestion is effective only in a relatively narrow area range, and information indicating the location of a parking lot is very small. Valid only in a small area.

The control unit 5 refers to the current position information provided from the position detection unit 3 for the information stored in the cache memory area C and having the effective range information attached as tag information. It is determined whether the vehicle is located within the effective area range. And if the vehicle is located within the effective area, the information is given a lower priority for replacement, and if the vehicle is outside the effective area, the information is Give high priority for replacement.

Furthermore, of the information which the information center 30 transmits, for information valid time is limited, and the effective time information is then associated with the tag information. For example, a restaurant lunchtime menu is unlikely to be accessed once a certain time is reached.
Therefore, the control unit 5 determines, for the information stored in the cache memory C that the valid time information is attached as the tag information, if the current time output from the clock 10 is within the valid time. The information is given a low priority for replacement, and if the current time is outside the valid time, the information is given a high priority for replacement.

The operation of the control unit 5 described above is performed in the ROM 1
The processing is realized by the program processing based on the control program stored in the storage unit 1, and the processing of the control unit 5 for the cache memory area C is functionally represented as shown in FIG. That is, position information is attached to the position-dependent information as tag information, and information having a limited effective area is accompanied by effective range information as tag information.
The valid time information is accompanied by the valid time information as tag information. These pieces of information are stored in the cache memory area C together with the tag information. That is, the cache memory area C functions as a storage unit and a determination basic information storage unit.

The control unit 5 controls the position information accompanying the position-dependent information in the cache memory area C and the position detection unit 3.
Functions as first comparing means 51 for comparing the current position information given from the first position information with the information on the traveling direction of the vehicle given from the position detection unit 3. When the vehicle has passed the position represented by the position information, a high priority for replacement is given to the position-dependent information. That is, the position-dependent information is invalidated with priority. In this case, the position detection unit 3 includes a current position measurement unit 61 that measures the current position of the vehicle,
And functions as a traveling direction estimating means 62 for estimating the traveling direction of the vehicle from the change in the current position.

The control unit 5 compares the effective range information associated with the information having a limited effective area range in the cache memory area C with the current position information provided from the position detection unit 3. Also has a function as the comparing means 52. Then, when the current position of the vehicle is outside the effective range, a high priority for replacement is given to the information whose effective range is limited.

Further, the control unit 5 compares the valid time information associated with the information on the limited valid time in the cache memory area C with the current time output from the clock 10. It also has a function as Then, when the current time is outside the valid time, a high priority for replacement is given to the information whose valid time is limited.

As described above, according to this embodiment, the information to be replaced is controlled by focusing on three elements, that is, position, area, and time, which are closely related to the information used in the vehicle navigation system. 5 is determined. Therefore, information that is unlikely to be required can be reliably invalidated and replaced with new information. As a result, an extremely efficient cache memory device is realized, and the cache hit rate can be improved.
The processing capacity of the entire vehicle navigation device can be increased.

Although one embodiment of the present invention has been described, it goes without saying that the present invention can adopt another embodiment. For example, in the above embodiment, the traveling direction of the vehicle is predicted based on the change in the current position. For example, in a navigation device having a route calculation function for calculating a recommended route to a destination, a recommended The traveling direction can be predicted based on the route.

Also, in the above embodiment, an example in which the present invention is applied to a vehicle navigation device has been described. However, the present invention can be widely applied to mobile computers other than the vehicle navigation device. In addition to the computer, the present invention can be effectively applied to a device that handles information whose degree of need increases or decreases depending on some measurable physical quantity.

In addition, various changes can be made within the scope described in the claims.

[0045]

According to the first or fifth aspect of the present invention, the information to be replaced is determined based on the measurement result of the physical quantity corresponding to the property of the information. It can be. as a result,
A more effective cache memory device than the conventional general method is realized.

That is, utilizing the positional dependence of information,
An efficient cache memory device can be realized. Claim 2
According to the invention of claim 6 , by determining the information to be replaced in consideration of the traveling direction of the information use point, a more efficient cache memory device can be realized.

According to the third or seventh aspect of the present invention,
If the information has an effective range, the information to be replaced is determined based on the comparison result between the current position and the effective range, so that an efficient cache memory device can be realized. According to the invention of claim 4 or claim 8 , when the information has a valid time, the information to be replaced is determined based on the comparison result between the current time and the valid time, so that an efficient cache memory is provided. The device can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a vehicle navigation device to which an embodiment of the present invention is applied.

FIG. 2 is a diagram for explaining a relationship between position-dependent information and a position and a traveling direction of a vehicle.

FIG. 3 is a block diagram illustrating a functional configuration related to control of a cache memory area;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Angular velocity sensor 2 Vehicle speed sensor 3 Position detection part 4 GPS receiver 5 Control part 10 Clock 15 RAM 20 Cellular phone C Cache memory area 51 First comparison means 52 Second comparison means 53 Third comparison means 61 Current position measurement Means 62 Travel direction prediction means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G06F 12/00 G01C 21/00 G08G 1/0969

Claims (8)

(57) [Claims] Storage means for temporarily storing 1. A information, the determination basic information defined based on the nature of the information, the
Basic judgment information stored for each piece of information stored in the storage means
Storage means, and measuring means for measuring a physical quantity corresponding to the basic determination information
And the result of measurement by the measuring means is stored in the basic information storage unit.
Compare with the basic judgment information stored in the column
Comparing means , based on a comparison result by the comparing means,
Out of the information stored in the storage means,
To determine what information should be replaced with
And the determination basic information is position information corresponding to information stored in the storage means, and the measurement means measures a current position corresponding to a use point of the information stored in the storage means. to include a current position measuring means, said comparing means, said current position current position measured by the measuring means, characterized and to Ruki catcher that is intended to include means for comparing the position information is the determination basic information Tsu memory device. Wherein said measuring means includes a further traveling direction predicting means for predicting the traveling direction of the use point information stored in said storage means, said comparing means, measured by the current position measuring means and the current position that is, when comparing the positional information is determined basic information, claim 1, characterized in that the consideration of the traveling direction is predicted by the traveling direction predicting means
A cache memory device according to claim 1. 3. A storage means for temporarily storing information, and a determination basic information determined based on a property of the information.
Basic judgment information stored for each piece of information stored in the storage means
Storage means, and measuring means for measuring a physical quantity corresponding to the basic determination information
And the result of measurement by the measuring means is stored in the basic information storage unit.
Compare with the basic judgment information stored in the column
Comparing means , based on a comparison result by the comparing means,
Out of the information stored in the storage means,
To determine what information should be replaced with
And the determination basic information is effective range information indicating an effective area range of the information stored in the storage means, and the measuring means corresponds to a use point of the information stored in the storage means. Current position measuring means for measuring a current position, wherein the comparing means determines whether or not the current position measured by the current position measuring means is within an effective area range corresponding to effective range information as the determination basic information. features and to Ruki Yasshumemori device that is intended to determine. 4. A storage means for temporarily storing information, and a determination basic information determined based on a property of the information,
Basic judgment information stored for each piece of information stored in the storage means
Storage means, and measuring means for measuring a physical quantity corresponding to the basic determination information
And the result of measurement by the measuring means is stored in the basic information storage unit.
Compare with the basic judgment information stored in the column
Comparing means , based on a comparison result by the comparing means,
Out of the information stored in the storage means,
To determine what information should be replaced with
And the determination basic information is valid time information indicating a valid time of the information stored in the storage means, and the measuring means is a current time corresponding to a use time of the information stored in the storage means. Current time measuring means for measuring time, wherein the comparing means determines whether or not the current time measured by the current time measuring means is within the valid time corresponding to the valid time information which is the determination basic information. features and to Ruki Yasshumemori device that is intended to determine. 5. A step for temporarily storing information in storage means.
And the nature of the information stored in the storage means.
The determined basic information is stored in the information stored in the storage means.
And storing the physical quantity corresponding to the determination basic information, and comparing the measured physical quantity with the determination basic information.
Out of the information stored in the storage means,
What information should be replaced with what should be stored
Determining, wherein the determination basic information is position information corresponding to the information stored in the storage means, and the physical quantity corresponding to the determination basic information is information stored in the storage means. features and to Ruki Yasshu control method that is a current position corresponding to that point. 6. The physical quantity corresponding to the basic judgment information includes:
The information processing apparatus further includes a traveling direction of the current position, and in the step of determining the information to be replaced, the current position and the traveling direction are compared with the position information as the determination basic information. The cache control method according to claim 5 . 7. A step for temporarily storing information in storage means.
And the nature of the information stored in the storage means.
The determined basic information is stored in the information stored in the storage means.
And storing the physical quantity corresponding to the determination basic information, and comparing the measured physical quantity with the determination basic information.
Out of the information stored in the storage means,
What information should be replaced with what should be stored
Determining, wherein the determination basic information is effective range information representing an effective area range of the information stored in the storage means, and a physical quantity corresponding to the determination basic information is stored in the storage means. The step of determining the information to be replaced is the current position corresponding to the point where the information is used. , replacement features and to Ruki Yasshu control method that the information of interest is determined. 8. A step for temporarily storing information in storage means.
And the nature of the information stored in the storage means.
The determined basic information is stored in the information stored in the storage means.
And storing the physical quantity corresponding to the determination basic information, and comparing the measured physical quantity with the determination basic information.
Out of the information stored in the storage means,
What information should be replaced with what should be stored
Determining, wherein the determination information is valid time information representing a valid time of the information stored in the storage means, and the physical quantity corresponding to the basic determination information is obtained by using the information stored in the storage means. In the step of determining the information to be replaced, the information to be replaced is determined based on whether or not the current time is within the valid time range represented by the valid time information. features and to Ruki Yasshu control method that but determined.