Contents
scnvcor - compute the convolution or correlation of real
vectors
SUBROUTINE SCNVCOR(CNVCOR, FOUR, NX, X, IFX, INCX, NY, NPRE, M, Y,
IFY, INC1Y, INC2Y, NZ, K, Z, IFZ, INC1Z, INC2Z, WORK, LWORK)
CHARACTER * 1 CNVCOR, FOUR
INTEGER NX, IFX, INCX, NY, NPRE, M, IFY, INC1Y, INC2Y, NZ,
K, IFZ, INC1Z, INC2Z, LWORK
REAL X(*), Y(*), Z(*), WORK(*)
SUBROUTINE SCNVCOR_64(CNVCOR, FOUR, NX, X, IFX, INCX, NY, NPRE, M, Y,
IFY, INC1Y, INC2Y, NZ, K, Z, IFZ, INC1Z, INC2Z, WORK, LWORK)
CHARACTER * 1 CNVCOR, FOUR
INTEGER*8 NX, IFX, INCX, NY, NPRE, M, IFY, INC1Y, INC2Y, NZ,
K, IFZ, INC1Z, INC2Z, LWORK
REAL X(*), Y(*), Z(*), WORK(*)
F95 INTERFACE
SUBROUTINE CNVCOR(CNVCOR, FOUR, [NX], X, IFX, [INCX], NY, NPRE, M, Y,
IFY, INC1Y, INC2Y, NZ, K, Z, IFZ, INC1Z, INC2Z, WORK, [LWORK])
CHARACTER(LEN=1) :: CNVCOR, FOUR
INTEGER :: NX, IFX, INCX, NY, NPRE, M, IFY, INC1Y, INC2Y,
NZ, K, IFZ, INC1Z, INC2Z, LWORK
REAL, DIMENSION(:) :: X, Y, Z, WORK
SUBROUTINE CNVCOR_64(CNVCOR, FOUR, [NX], X, IFX, [INCX], NY, NPRE, M,
Y, IFY, INC1Y, INC2Y, NZ, K, Z, IFZ, INC1Z, INC2Z, WORK, [LWORK])
CHARACTER(LEN=1) :: CNVCOR, FOUR
INTEGER(8) :: NX, IFX, INCX, NY, NPRE, M, IFY, INC1Y, INC2Y,
NZ, K, IFZ, INC1Z, INC2Z, LWORK
REAL, DIMENSION(:) :: X, Y, Z, WORK
C INTERFACE
#include <sunperf.h>
void scnvcor(char cnvcor, char four, int nx, float *x, int
ifx, int incx, int ny, int npre, int m, float *y,
int ify, int inc1y, int inc2y, int nz, int k,
float *z, int ifz, int inc1z, int inc2z, float
*work, int lwork);
void scnvcor_64(char cnvcor, char four, long nx, float *x,
long ifx, long incx, long ny, long npre, long m,
float *y, long ify, long inc1y, long inc2y, long
nz, long k, float *z, long ifz, long inc1z, long
inc2z, float *work, long lwork);
scnvcor computes the convolution or correlation of real vec-
tors.
CNVCOR (input)
'V' or 'v' if convolution is desired, 'R' or 'r'
if correlation is desired.
FOUR (input)
'T' or 't' if the Fourier transform method is to
be used, 'D' or 'd' if the computation should be
done directly from the definition. The Fourier
transform method is generally faster, but it may
introduce noticeable errors into certain results,
notably when both the filter and data vectors con-
sist entirely of integers or vectors where ele-
ments of either the filter vector or a given data
vector differ significantly in magnitude from the
1-norm of the vector.
NX (input)
Length of the filter vector. NX >= 0. SCNVCOR
will return immediately if NX = 0.
X (input)
Filter vector.
IFX (input)
Index of the first element of X. NX >= IFX >= 1.
INCX (input)
Stride between elements of the filter vector in X.
INCX > 0.
NY (input)
Length of the input vectors. NY >= 0. SCNVCOR
will return immediately if NY = 0.
NPRE (input)
The number of implicit zeros prepended to the Y
vectors. NPRE >= 0.
M (input)
Number of input vectors. M >= 0. SCNVCOR will
return immediately if M = 0.
Y (input)
Input vectors.
IFY (input)
Index of the first element of Y. NY >= IFY >= 1.
INC1Y (input)
Stride between elements of the input vectors in Y.
INC1Y > 0.
INC2Y (input)
Stride between the input vectors in Y. INC2Y > 0.
NZ (input)
Length of the output vectors. NZ >= 0. SCNVCOR
will return immediately if NZ = 0. See the Notes
section below for information about how this argu-
ment interacts with NX and NY to control circular
versus end-off shifting.
K (input)
Number of Z vectors. K >= 0. If K = 0 then
SCNVCOR will return immediately. If K < M then
only the first K input vectors will be processed.
If K > M then M input vectors will be processed.
Z (output)
Result vectors.
IFZ (input)
Index of the first element of Z. NZ >= IFZ >= 1.
INC1Z (input)
Stride between elements of the output vectors in
Z. INC1Z > 0.
INC2Z (input)
Stride between the output vectors in Z. INC2Z >
0.
WORK (input/output)
Scratch space. Before the first call to SCNVCOR
with particular values of the integer arguments
the first element of WORK must be set to zero. If
WORK is written between calls to SCNVCOR or if
SCNVCOR is called with different values of the
integer arguments then the first element of WORK
must again be set to zero before each call. If
WORK has not been written and the same values of
the integer arguments are used then the first ele-
ment of WORK to zero. This can avoid certain ini-
tializations that store their results into WORK,
and avoiding the initialization can make SCNVCOR
run faster.
LWORK (input)
Length of WORK. LWORK >= 4*max(NX,NPRE+NY,NZ)+15.
If any vector overlaps a writable vector, either because of
argument aliasing or ill-chosen values of the various INC
arguments, the results are undefined and may vary from one
run to the next.
The most common form of the computation, and the case that
executes fastest, is applying a filter vector X to a series
of vectors stored in the columns of Y with the result placed
into the columns of Z. In that case, INCX = 1, INC1Y = 1,
INC2Y >= NY, INC1Z = 1, INC2Z >= NZ. Another common form is
applying a filter vector X to a series of vectors stored in
the rows of Y and store the result in the row of Z, in which
case INCX = 1, INC1Y >= NY, INC2Y = 1, INC1Z >= NZ, and
INC2Z = 1.