mxvg_c |

Table of contents## Proceduremxvg_c ( Matrix times vector, general dimension ) void mxvg_c ( const void * m1, const void * v2, SpiceInt nr1, SpiceInt nc1r2, void * vout ) ## AbstractMultiply a matrix and a vector of arbitrary size. ## Required_ReadingNone. ## KeywordsMATRIX VECTOR ## Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- m1 I Left-hand matrix to be multiplied. v2 I Right-hand vector to be multiplied. nr1 I Row dimension of `m1' and length of `vout'. nc1r2 I Column dimension of `m1' and length of `v2'. vout O Product vector m1*v2. ## Detailed_Inputm1 is a double precision matrix of arbitrary size which forms the left-hand matrix of the multiplication. v2 is a double precision vector on the right of the multiplication. nr1 is the row dimension of `m1' and length of `vout'. nc1r2 is the column dimension of `m1' and length of `v2'. ## Detailed_Outputvout is the double precision vector which results from the multiplication vout = (m1) x v2 `vout' has length `nr1'. `vout' may overwrite `m1' or `v2'. ## ParametersNone. ## Exceptions1) If memory cannot be allocated to create the temporary matrix required for the execution of the routine, the error SPICE(MALLOCFAILED) is signaled. ## FilesNone. ## ParticularsThe code reflects precisely the following mathematical expression For each value of the subscript `i' from 1 to `nr1', vout(i) = Summation from k=1 to nc1r2 of ( m1(i,k) * v2(k) ) ## ExamplesThe numerical results shown for this example may differ across platforms. The results depend on the SPICE kernels used as input, the compiler and supporting libraries, and the machine specific arithmetic implementation. 1) Given a 2x3 matrix and a 3-vector, multiply the matrix by the vector. Example code begins here. /. Program mxvg_ex1 ./ #include <stdio.h> #include "SpiceUsr.h" int main( ) { /. Local variables. ./ SpiceDouble vout [2]; /. Define `m' and `vin'. ./ SpiceDouble m [2][3] = { { 1.0, 1.0, 1.0 }, { 2.0, 3.0, 4.0 } }; SpiceDouble vin [3] = { 1.0, 2.0, 3.0 }; /. Multiply `m' by `vin'. ./ ## Restrictions1) The user is responsible for checking the magnitudes of the elements of `m1' and `v2' so that a floating point overflow does not occur. ## Literature_ReferencesNone. ## Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) W.L. Taber (JPL) ## Version-CSPICE Version 1.2.0, 04-JUL-2021 (JDR) Changed input argument name "nrow1" to "nr1" for consistency with other routines. Updated short error message for consistency within CSPICE wrapper interface: MEMALLOCFAILED -> MALLOCFAILED. Edited the header to comply with NAIF standard. Added complete code example based on the existing example. -CSPICE Version 1.1.0, 25-JUL-2001 (NJB) Changed protoype: inputs "m1" and "v2" are now type (const void *). Implemented interface macro for casting inputs "m1" and "v2" to const. -CSPICE Version 1.0.1, 08-FEB-1998 (NJB) Corrected a comment describing the local macro INDEX. Made miscellaneous code format corrections. -CSPICE Version 1.0.0, 25-OCT-1997 (NJB) (WLT) Based on SPICELIB Version 1.0.1, 10-MAR-1992 (WLT) ## Index_Entriesmatrix times n-dimensional vector |

Fri Dec 31 18:41:09 2021