Delay analyzing method, delay analyzing apparatus, and computer product

Abstract

A delay analyzing apparatus receives a result of timing analysis of a target circuit, and detects, from paths in the target circuit, critical paths based on the result of the timing analysis with a detecting unit. A first calculating unit calculates an average delay distribution of the paths other than the critical paths based on an average delay value of each of the critical paths. A second calculating unit calculates a probability density distribution of the critical paths, and a third calculating unit calculates a probability density distribution of all of the paths based on the average delay distribution. A fourth calculating unit calculates difference between a statistical delay value of the critical paths and a statistical delay value of all of the paths based on the probability density distribution of the critical paths and the probability density distribution of all of the paths.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a delay analyzing apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic of a circuit element library;

FIG. 3A is a circuit diagram of an analysis target circuit according to the embodiment;

FIG. 3B is a schematic of critical paths;

FIG. 4 is a schematic of a timing list;

FIG. 5 is a block diagram of a delay analyzing apparatus 500 according to the embodiment;

FIG. 6 is a schematic of a probability density distribution of the delay;

FIG. 7 is a graph of an average delay value with respect to the number of path;

FIG. 8 is a schematic of a partial circuit according to the embodiment;

FIG. 9 is a schematic for explaining a probability density distribution and an accumulated probability distribution of the delay;

FIG. 10 is a chart of the probability density distribution calculated from the average delay distribution shown in FIG. 7;

FIG. 11 is a schematic of an option added to an execution command of a timing analysis;

FIG. 12 is a flowchart of a delay analyzing process by the delay analyzing apparatus 500;

FIG. 13 is a flowchart of a critical path detecting process;

FIG. 14 is a flowchart of a probability density distribution calculating process for the critical paths;

FIG. 15 is a flowchart of a partial circuit creating process; and

FIG. 16 is a flowchart of a probability density distribution calculating process for the entire circuit.

Claims

1. A computer-readable recording medium that stores therein a delay analyzing program making a computer execute: receiving a result of timing analysis of a target circuit;detecting, from paths in the target circuit, critical paths of which a delay value is within a predetermined range based on the result of the timing analysis;calculating an average delay distribution of paths other than the critical paths based on an average delay value of each of the critical paths;calculating a probability density distribution of the critical paths based on a probability density distribution of delay of each circuit element constituting the critical paths;calculating a probability density distribution of all of the paths based on the probability density distribution of the critical paths and the average delay distribution; andcalculating difference between a statistical delay value of the critical paths and a statistical delay value of all of the paths based on the probability density distribution of the critical paths and the probability density distribution of all of the paths.

2. The computer-readable recording medium according to claim 1, wherein the delay analyzing program further makes the computer execute calculating a probability density distribution of the paths other than the critical paths based on the average delay distribution, and the calculating a probability density distribution of all of the paths includes calculating the probability density distribution of all of the paths based on the probability density distribution of the critical path and the probability density distribution of the paths other than the critical paths.

3. The computer-readable recording medium according to claim 1, wherein the delay analyzing program further makes the computer execute correcting the statistical delay value of the critical paths based on the difference.

4. The computer-readable recording medium according to claim 3, wherein the delay analyzing program further makes the computer execute judging whether the difference is equal to or smaller than a threshold, andthe correcting includes correcting the probability delay value of the critical paths based on an error when it is judged that the difference is not equal to or smaller than the threshold at the judging.

5. The computer-readable recording medium according to claim 1, wherein the delay analyzing program further makes the computer execute: identifying a valid path being a path of which the average delay value is equal to or larger than a reference value among the paths other than the critical paths, based on the average delay distribution of the paths other than the critical paths and the probability density distribution of the critical paths;extracting the probability density distribution of the valid path from the probability density distribution of all of the paths; andcalculating difference between the statistical delay value of the critical paths and a statistical delay value of the valid path based on the probability density distribution of the critical path and the probability density distribution of the valid path.

6. The computer-readable recording medium according to claim 5, wherein the delay analyzing program further makes the computer execute judging whether the difference is equal to or smaller than a threshold, andthe identifying includes identifying the valid path when it is judged that the difference is not equal to or smaller than the threshold at the judging.

7. The computer-readable recording medium according to claim 1, wherein the delay analyzing program further makes the computer execute displaying on a display screen information on a path of which the average delay value is equal to or larger than a reference value among the paths other than the critical paths, based on the average delay distribution of the paths other than the critical paths and the probability density distribution of the critical paths.

8. A delay analyzing method comprising: receiving a result of timing analysis of a target circuit;detecting, from paths in the target circuit, critical paths of which a delay value is within a predetermined range based on the result of the timing analysis;calculating an average delay distribution of the paths other than the critical paths based on an average delay value of each of the critical paths;calculating a probability density distribution of the critical paths based on a probability density distribution of delay of each circuit element constituting the critical paths;calculating a probability density distribution of all of the paths included in the target circuit based on the probability density distribution of the critical paths and the average delay distribution; andcalculating difference between a statistical delay value of the critical paths and a statistical delay value of all of the paths based on the probability density distribution of the critical paths and the probability density distribution of all of the paths.

9. The delay analyzing method according to claim 8, further comprising calculating a probability density distribution of the paths other than the critical paths based on the average delay distribution, wherein the calculating a probability density distribution of all of the paths includes calculating the probability density distribution of all of the paths based on the probability density distribution of the critical path and the probability density distribution of the paths other than the critical paths.

10. The delay analyzing method according to claim 8, further comprising correcting the statistical delay value of the critical paths based on the difference.

11. The delay analyzing method according to claim 10, further comprising judging whether the difference is equal to or smaller than a threshold, wherein the correcting includes correcting the probability delay value of the critical paths based on an error when it is judged that the difference is not equal to or smaller than the threshold at the judging.

12. The delay analyzing method according to claim 8, further comprising: identifying a valid path being a path of which the average delay value is equal to or larger than a reference value among the paths other than the critical paths, based on the average delay distribution of the paths other than the critical paths and the probability density distribution of the critical paths;extracting the probability density distribution of the valid path from the probability density distribution of all of the paths; andcalculating difference between the statistical delay value of the critical paths and a statistical delay value of the valid path based on the probability density distribution of the critical path and the probability density distribution of the valid path.

13. The delay analyzing method according to claim 12, further comprising judging whether the difference is equal to or smaller than a threshold, wherein the identifying includes identifying the valid path when it is judged that the difference is not equal to or smaller than the threshold at the judging.

14. A delay analyzing apparatus comprising: a receiving unit configured to receive a result of timing analysis of a target circuit;a detecting unit configured to detect, from paths in the target circuit, critical paths of which a delay value is within a predetermined range based on the result of the timing analysis;a first calculating unit configured to calculate an average delay distribution of the paths other than the critical paths based on an average delay value of each of the critical paths;a second calculating unit configured to calculate a probability density distribution of the critical paths based on a probability density distribution of delay of each circuit element constituting the critical paths;a third calculating unit configured to calculate a probability density distribution of all of the paths included in the target circuit based on the probability density distribution of the critical paths and the average delay distribution; anda fourth calculating unit configured to calculate difference between a statistical delay value of the critical paths and a statistical delay value of all of the paths based on the probability density distribution of the critical paths and the probability density distribution of all of the paths.

15. The delay analyzing apparatus according to claim 14, further comprising a fifth calculating unit configured to calculate a probability density distribution of the paths other than the critical paths based on the average delay distribution, and the third calculating unit calculates the probability density distribution of all of the paths based on the probability density distribution of the critical path and the probability density distribution of the paths other than the critical paths.

16. The delay analyzing apparatus according to claim 14, further comprising a correcting unit configured to correct the statistical delay value of the critical paths based on the difference.

17. The delay analyzing apparatus according to claim 16, further comprising a first judging unit configured to judge whether the difference is equal to or smaller than a threshold, wherein the correcting unit corrects the probability delay value of the critical paths based on an error when it is judged that the difference is not equal to or smaller than the threshold by the first judging unit.

18. The delay analyzing apparatus according to claim 14, further comprising: an identifying unit configured to identify a valid path being a path of which the average delay value is equal to or larger than a reference value among the paths other than the critical paths, based on the average delay distribution of the paths other than the critical paths and the probability density distribution of the critical paths;an extracting unit configured to extract the probability density distribution of the valid path from the probability density distribution of all of the paths; anda sixth calculating unit configured to calculate difference between the statistical delay value of the critical paths and a statistical delay value of the valid path based on the probability density distribution of the critical path and the probability density distribution of the valid path.

19. The delay analyzing apparatus according to claim 18, further comprising a second judging unit configured to judge whether the difference is equal to or smaller than a threshold, wherein the identifying unit identifies the valid path when it is judged that the difference is not equal to or smaller than the threshold by the second judging unit.