vsip_dvmprod_p - Vector-Matrix Product

Core

6.1.8 vsip_dvmprod_p - Vector-Matrix Product

void vsip_vmprod_f(const vsip_vview_f *a, const vsip_mview_f *b, const vsip_vview_f *r); 
void vsip_cvmprod_f(const vsip_cvview_f *a, const vsip_cmview_f *b, const vsip_cvview_f *r);

Description

This function computes the product of a vector and a matrix, storing the result in an output vector. The operation performed is:

r =∑︁n a ·b i j=1 j j,i

for $i= 1,2,...,m$ , where $a$ is a vector of length $n$ , $b$ is an $n ×m$ matrix, and $r$ is the resulting vector of length $m$ .

This operation is equivalent to the matrix-vector product $T r= a ·b$ , where $T a$ is the transpose of vector $a$ .

Parameters

const vsip_dvview_p* a: Input vector of length $n$ .
const vsip_dmview_p* b: Input matrix of size $n ×m$ .
const vsip_dvview_p* r: Output vector of length $m$ that will store the result.

Example

vsip_vview_f *a, *r; 
vsip_mview_f *b; 
vsip_length n = 4, m = 3; 
 
// Create vector and matrices 
a = vsip_vcreate_f(n, VSIP_MEM_NONE); 
b = vsip_mcreate_f(n, m, VSIP_ROW, VSIP_MEM_NONE); 
r = vsip_vcreate_f(m, VSIP_MEM_NONE); 
 
// Initialize vector a and matrix b with some values 
vsip_vramp_f(1.0f, 1.0f, a);  // a = [1, 2, 3, 4] 
 
// Initialize matrix b (4x3) 
for (vsip_index i = 0; i < n; i++) { 
    for (vsip_index j = 0; j < m; j++) { 
        vsip_mput_f(b, i, j, (float)(i*m + j + 1)); 
    } 
} 
 
// Compute vector-matrix product: r = a^T * b 
vsip_vmprod_f(a, b, r); 
 
// Print the result 
printf("Result vector r:\n"); 
for (vsip_index i = 0; i < m; i++) { 
    printf("%8.2f ", vsip_vget_f(r, i)); 
} 
printf("\n"); 
 
// Clean up 
vsip_valldestroy_f(a); 
vsip_malldestroy_f(b); 
vsip_valldestroy_f(r);

Notes

The input vector $a$ must have length $n$ .
The input matrix $b$ must have dimensions $n ×m$ .
The output vector $r$ must have length $m$ .
This operation is equivalent to the matrix-vector product $T r= a ·b$ .
This operation is not commutative: $T T a ·b ̸=b ·a$ .

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