Computer Programs
NESC1082 SIGPI.
last modified: 07-DEC-1989 | catalog | categories | new | search |

# NESC1082 SIGPI.

#### SIGPI, Probabilistic System Performance by Fault-Tree Analysis

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1. NAME OR DESIGNATION OF PROGRAM:  SIGPI.
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2. COMPUTERS
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Program name Package id Status Status date
SIGPI NESC1082/01 Tested 07-DEC-1989
SIGPI NESC1082/02 Tested 07-DEC-1989

Machines used:

Package ID Orig. computer Test computer
NESC1082/01 Many Computers CRAY X-MP
NESC1082/02 DEC VAX 11/750 DEC VAX 8810
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3. DESCRIPTION OF PROGRAM OR FUNCTION

SIGPI computes the probabilistic performance of complex systems by combining cut set or other binary product data with probability information on each basic event. SIGPI is designed to work with either coherent systems, where the system fails when certain combinations of components fail, or noncoherent systems, where at least one cut set occurs only if at least one component of the system is operating properly. The program can handle conditionally independent components, dependent components, or a combination of component types and has been used to evaluate responses to environmental threats and seismic events. The  three data types that can be input are cut set data in disjoint normal form, basic component probabilities for independent basic components, and mean and covariance data for statistically dependent basic components.
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4. METHOD OF SOLUTION

SIGPI uses two fast complementary methods to compute the probabilistic performance of complex systems: the pi method and the sigma method. The pi method exploits the fact that defined system components are often statistically independent conditional to the environment in which they are embedded. The sigma method computes the probability of combinations of components produced by the pi method by disjointing and partitioning the components, thereby allowing the exact computation of performance. The computational complexity of the overall process is a polynomial  function of the number of components. When statistical independence  is not possible, dependent data can be used in the calculation, although both speed and accuracy may suffer.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM:
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6. TYPICAL RUNNING TIME

The running time depends on the complexity of the problem. The same problems required from 3.8 seconds to 53 minutes on the DEC VAX11/785 and from 0.1 to 5.3 seconds on the CDC  CYBER170/875.
NESC1082/01
NEA-DB ran the test cases included in this package on a CRAY-XMP/2800 computer. CPU times varied from 6.1 to 9.5 seconds.

NESC1082/02
NEA-DB ran the test cases included in this package in interactive mode on a VAX 8810 computer.
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7. UNUSUAL FEATURES OF THE PROGRAM

For super-large problems, where costs of precise answers may be prohibitive, a desired accuracy can  be specified, and the sigma-pi algorithms will halt when this accuracy is achieved.
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8. RELATED AND AUXILIARY PROGRAMS

SIGPI calls the SLATEC (NESC 820) error handling software, which is available from NESC as the XERROR  package (NESC 988). The auxiliary program CONVI is included to interactively convert the formatted test data to binary for SIGPI use.
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9. STATUS
Package ID Status date Status
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10. REFERENCES:
NESC1082/01, included references:
- C. Yuelys-Miksis:
SIGPI Cray, CDC (Single-Precision) Version Tape
Description and Implementation Information.
NESC Note 88-80  (June 30, 1988)
- C.J. Patenaude:
SIGPI: A User's Manual for Fast Computation of the Probabilistic
Performance of Complex Systems.
NUREG/CR-4800, UCID-20679 (September 1986).
NESC1082/02, included references:
- C. Yuelys-Miksis:
SIGPI DEC VAX (Double-Precision) Version Tape
Description and Implementation Information.
NESC Note 88-79  (June 30, 1988)
- C.J. Patenaude:
SIGPI: A User's Manual for Fast Computation of the Probabilistic
Performance of Complex Systems.
NUREG/CR-4800, UCID-20679 (September 1986).
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11. MACHINE REQUIREMENTS

1.85 Mbytes (DEC VAX11), 203,000 (octal) words (CDC CYBER170).
NESC1082/01
On CDC CYBER 830, 450,000 (octal) words of main storage are required to run the test cases.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC1082/01 FORTRAN-77
NESC1082/02 FORTRAN-77
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED

VMS 4.0, 4.5 (DEC VAX11), CTSS (Cray1), NOS 2.4.3 (CDC CYBER170/875).
NESC1082/01
COS 1.17 (CRAY-XMP/2800) with CFT 1.14 compiler.

NESC1082/02
VMS V5.0-1 (VAX8810) with FORTRAN V5.0-1 compiler.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

Full-word Boolean operations AND, OR, and NOT must be available. The test problem output produced with the DEC VAX version may differ from the output shown in the reference document due to variations in operating systems and available memory. The dependent case test problems can be run on a CDC only if LCM is available. A dummy XERROR subroutine is included in the Cray, CDC version of SIGPI. The Cray version may be run on CDC machines by disabling the lines with  - CRAY - in columns 73-78 and enabling those with --CDC-- in columns 73-78 as well as utilizing the appropriate machine constants in Function RIMACH, and presetting memory to zero.
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15. NAME AND ESTABLISHMENT OF AUTHORS

C.J. Patenaude
Lawrence Livermore National Laboratory
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16. MATERIAL AVAILABLE
NESC1082/01
File name File description Records
NESC1082_01.001 Information file 175
NESC1082_01.002 SSIG.FOR 1901
NESC1082_01.003 CSIG.FOR 1433
NESC1082_01.004 FUN.FOR 1460
NESC1082_01.005 PDEP.FOR 511
NESC1082_01.006 PRE.FOR 663
NESC1082_01.007 SD.FOR 3365
NESC1082_01.008 SDC.FOR 1743
NESC1082_01.009 SDP.FOR 819
NESC1082_01.010 SIO.FOR 304
NESC1082_01.011 DPDEP.FOR 678
NESC1082_01.012 XERROR.DUM 3
NESC1082_01.013 XERROR.FOR 1053
NESC1082_01.014 DTEST.DAT 17
NESC1082_01.015 PTEST.DAT 114
NESC1082_01.016 TEST1.DAT 5
NESC1082_01.017 TEST2.DAT 5
NESC1082_01.018 TEST3.DAT 20
NESC1082_01.019 TEST4.DAT 20
NESC1082_01.020 SMPL1.DAT 1
NESC1082_01.021 SMPL2.DAT 2
NESC1082_01.022 SMPL3.DAT 2
NESC1082_01.023 SMPL4.DAT 2
NESC1082_01.024 SMPL5.DAT 2
NESC1082_01.025 SMPL6.DAT 2
NESC1082_01.026 SMPL7.DAT 2
NESC1082_01.027 SMPL8.DAT 2
NESC1082_01.028 Print out of smple problem B.4.1 139
NESC1082_01.029 Print out of smple problem B.4.2 137
NESC1082_01.030 Print out of smple problem B.4.5 165
NESC1082_01.031 Print out of smple problem B.4.6 164
NESC1082_01.032 CONVI.FOR 24
NESC1082_01.033 CRAY JCL 41
NESC1082/02
File name File description Records
NESC1082_02.001 INFORMATION FILE 110
NESC1082_02.002 SSIG.FOR 1779
NESC1082_02.003 CSIG.FOR 1353
NESC1082_02.004 FUN.FOR 1155
NESC1082_02.005 PRE.FOR 637
NESC1082_02.006 PDEP.FOR 511
NESC1082_02.007 SD.FOR 3212
NESC1082_02.008 SDC.FOR 1652
NESC1082_02.009 SDP.FOR 764
NESC1082_02.010 SIO.FOR 277
NESC1082_02.011 DPDEP.FOR 679
NESC1082_02.012 DTEST.DAT 17
NESC1082_02.013 PTEST.DAT 114
NESC1082_02.014 TEST1.DAT 5
NESC1082_02.015 TEST2.DAT 5
NESC1082_02.016 TEST3.DAT 20
NESC1082_02.017 TEST4.DAT 20
NESC1082_02.018 PRINTOUT OF SAMPLE PROBLEM B.4.1 3
NESC1082_02.019 PRINTOUT OF SAMPLE PROBLEM B.4.2 3
NESC1082_02.020 PRINTOUT OF SAMPLE PROBLEM B.4.3 9
NESC1082_02.021 PRINTOUT OF SAMPLE PROBLEM B.4.4 9
NESC1082_02.022 PRINTOUT OF SAMPLE PROBLEM B.4.5 5
NESC1082_02.023 PRINTOUT OF SAMPLE PROBLEM B.4.6 5
NESC1082_02.024 PRINTOUT OF SAMPLE PROBLEM B.4.7 11
NESC1082_02.025 PRINTOUT OF SAMPLE PROBLEM B.4.8 4
NESC1082_02.026 CONVI.FOR 29
NESC1082_02.027 SIGPI.OPT 5
NESC1082_02.028 SIGPI.COM 21
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17. CATEGORIES
• G. Radiological Safety, Hazard and Accident Analysis

Keywords: fault tree analysis, mathematical models, probability, system failure analysis.