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eis_ortran.c File Reference
#include "f2c.h"
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Functions | |
int | ortran_ (integer *nm, integer *n, integer *low, integer *igh, doublereal *a, doublereal *ort, doublereal *z__) |
Function Documentation
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Definition at line 8 of file eis_ortran.c.
00010 { 00011 /* System generated locals */ 00012 integer a_dim1, a_offset, z_dim1, z_offset, i__1, i__2, i__3; 00013 00014 /* Local variables */ 00015 static doublereal g; 00016 static integer i__, j, kl, mm, mp, mp1; 00017 00018 00019 00020 /* THIS SUBROUTINE IS A TRANSLATION OF THE ALGOL PROCEDURE ORTRANS, */ 00021 /* NUM. MATH. 16, 181-204(1970) BY PETERS AND WILKINSON. */ 00022 /* HANDBOOK FOR AUTO. COMP., VOL.II-LINEAR ALGEBRA, 372-395(1971). */ 00023 00024 /* THIS SUBROUTINE ACCUMULATES THE ORTHOGONAL SIMILARITY */ 00025 /* TRANSFORMATIONS USED IN THE REDUCTION OF A REAL GENERAL */ 00026 /* MATRIX TO UPPER HESSENBERG FORM BY ORTHES. */ 00027 00028 /* ON INPUT */ 00029 00030 /* NM MUST BE SET TO THE ROW DIMENSION OF TWO-DIMENSIONAL */ 00031 /* ARRAY PARAMETERS AS DECLARED IN THE CALLING PROGRAM */ 00032 /* DIMENSION STATEMENT. */ 00033 00034 /* N IS THE ORDER OF THE MATRIX. */ 00035 00036 /* LOW AND IGH ARE INTEGERS DETERMINED BY THE BALANCING */ 00037 /* SUBROUTINE BALANC. IF BALANC HAS NOT BEEN USED, */ 00038 /* SET LOW=1, IGH=N. */ 00039 00040 /* A CONTAINS INFORMATION ABOUT THE ORTHOGONAL TRANS- */ 00041 /* FORMATIONS USED IN THE REDUCTION BY ORTHES */ 00042 /* IN ITS STRICT LOWER TRIANGLE. */ 00043 00044 /* ORT CONTAINS FURTHER INFORMATION ABOUT THE TRANS- */ 00045 /* FORMATIONS USED IN THE REDUCTION BY ORTHES. */ 00046 /* ONLY ELEMENTS LOW THROUGH IGH ARE USED. */ 00047 00048 /* ON OUTPUT */ 00049 00050 /* Z CONTAINS THE TRANSFORMATION MATRIX PRODUCED IN THE */ 00051 /* REDUCTION BY ORTHES. */ 00052 00053 /* ORT HAS BEEN ALTERED. */ 00054 00055 /* QUESTIONS AND COMMENTS SHOULD BE DIRECTED TO BURTON S. GARBOW, */ 00056 /* MATHEMATICS AND COMPUTER SCIENCE DIV, ARGONNE NATIONAL LABORATORY 00057 */ 00058 00059 /* THIS VERSION DATED AUGUST 1983. */ 00060 00061 /* ------------------------------------------------------------------ 00062 */ 00063 00064 /* .......... INITIALIZE Z TO IDENTITY MATRIX .......... */ 00065 /* Parameter adjustments */ 00066 z_dim1 = *nm; 00067 z_offset = z_dim1 + 1; 00068 z__ -= z_offset; 00069 --ort; 00070 a_dim1 = *nm; 00071 a_offset = a_dim1 + 1; 00072 a -= a_offset; 00073 00074 /* Function Body */ 00075 i__1 = *n; 00076 for (j = 1; j <= i__1; ++j) { 00077 00078 i__2 = *n; 00079 for (i__ = 1; i__ <= i__2; ++i__) { 00080 /* L60: */ 00081 z__[i__ + j * z_dim1] = 0.; 00082 } 00083 00084 z__[j + j * z_dim1] = 1.; 00085 /* L80: */ 00086 } 00087 00088 kl = *igh - *low - 1; 00089 if (kl < 1) { 00090 goto L200; 00091 } 00092 /* .......... FOR MP=IGH-1 STEP -1 UNTIL LOW+1 DO -- .......... */ 00093 i__1 = kl; 00094 for (mm = 1; mm <= i__1; ++mm) { 00095 mp = *igh - mm; 00096 if (a[mp + (mp - 1) * a_dim1] == 0.) { 00097 goto L140; 00098 } 00099 mp1 = mp + 1; 00100 00101 i__2 = *igh; 00102 for (i__ = mp1; i__ <= i__2; ++i__) { 00103 /* L100: */ 00104 ort[i__] = a[i__ + (mp - 1) * a_dim1]; 00105 } 00106 00107 i__2 = *igh; 00108 for (j = mp; j <= i__2; ++j) { 00109 g = 0.; 00110 00111 i__3 = *igh; 00112 for (i__ = mp; i__ <= i__3; ++i__) { 00113 /* L110: */ 00114 g += ort[i__] * z__[i__ + j * z_dim1]; 00115 } 00116 /* .......... DIVISOR BELOW IS NEGATIVE OF H FORMED IN ORTHES. 00117 */ 00118 /* DOUBLE DIVISION AVOIDS POSSIBLE UNDERFLOW ...... 00119 .... */ 00120 g = g / ort[mp] / a[mp + (mp - 1) * a_dim1]; 00121 00122 i__3 = *igh; 00123 for (i__ = mp; i__ <= i__3; ++i__) { 00124 /* L120: */ 00125 z__[i__ + j * z_dim1] += g * ort[i__]; 00126 } 00127 00128 /* L130: */ 00129 } 00130 00131 L140: 00132 ; 00133 } 00134 00135 L200: 00136 return 0; 00137 } /* ortran_ */ |