GEN_SORTX ( order, status, type, size, n, x, incx, index )
order character*1 On entry, order specifies the operation to be performed as follows: If order = 'A' or 'a', x is sorted in ascending sequence If order = 'D' or 'd', x is sorted in descending sequence On exit, order is unchanged. status character*1 On entry, status specifies the operation to be performed as follows: If status = 'N' or 'n', the index vector is new (empty) on input. Elements of data vector x are initially accessed in sequential order. If stat = 'O' or 'o', the index vector is old (full) on input. Elements of data vector x are initially accessed in the order specified by the index vector. On exit, status is unchanged. type character*1 On entry, type specifies the data type of data vector x. The following types are valid: If type = 'B' or 'b', binary (unsigned integer) If type = 'C' or 'c', character string If type = 'I' or 'i', integer (signed) If type = 'L' or 'l', logical - Fortran .TRUE. or .FALSE. If type = 'R' or 'r', IEEE floating point If type = 'V' or 'v', VAXG floating point On exit, type is unchanged. size integer*4 On entry, size specifies the size, in bytes, of each element of data vector x. Valid combinations of type and size are shown below: If type = 'B' or 'b' - size = { 1,2,4,8 } If type = 'C' or 'c' - size = { 0 < size < 65536 } If type = 'I' or 'i' - size = { 1,2,4,8 } If type = 'L' or 'l' - size = { 1,2,4,8 } If type = 'R' or 'r' - size = { 4,8,16 } If type = 'V' or 'v' - size = { 4,8 } On exit, size is unchanged. n integer*4 On entry, the length of the x vector. On exit, n is unchanged. x data vector On entry, a length n vector of data to be sorted. Each element of vector x is of type and size specified. On exit, x is unchanged. incx integer*4 On entry, incx specifies the distance between elements of vector x. incx must be positive. On exit, incx is unchanged. index integer*4 On entry, vector index is ignored if status is 'N' or 'n', and used as an index vector for data vector x if status is 'O' or 'o'. On exit, vector index is overwritten by a permuted vector of indices that may be used to access data vector x in the sorted order specified by order.
GEN_SORTX is a general purpose, in memory, indexed sort routine. GEN_SORTX accepts the following FORTRAN data types: INTEGER*1, INTEGER*2, INTEGER*4, INTEGER*8 LOGICAL*1, LOGICAL*2, LOGICAL*4, LOGICAL*8 REAL*4, REAL*8, REAL*16 CHARACTER*(*) GEN_SORTX also accepts unsigned "binary" integers of 1, 2, 4, or 8 byte sizes. An indexed radix algorithm is employed to sort the data. For all data types except REAL*16 and CHARACTER*(*), an N*16 byte work space is acquired from heap storage. For REAL*16 data, a work space of N*24 bytes is taken from heap storage. Heap work space required for CHARACTER data is of size N*((SIZE-1)/8+3)*8 bytes. GEN_SORTX does not return a sorted vector. Instead, it returns an index vector index, which may be used to access data in the collating sequence specified by order. GEN_SORTX is stable and may be used to perform multi-key record sorts.
REAL DATA( 100 ) INTEGER INDEX( 100 ) N = 100 CALL GEN_SORTX( 'Descend','New','Real',SIZEOF(DATA(1)),N,DATA,1,INDEX ) DO I=1,N PRINT *,DATA(I),DATA( INDEX(I) ) ENDDO This FORTRAN code sorts a 100 element single precision real vector by index, leaving the data unchanged. Unsorted and sorted data are printed in adjacent columns.