# Sparse Level 1 Functions#

The sparse level 1 routines describe operations between a vector in sparse format and a vector in dense format. This section describes all hipSPARSE level 1 sparse linear algebra functions.

## hipsparseXaxpyi()#

hipsparseStatus_t hipsparseSaxpyi(hipsparseHandle_t handle, int nnz, const float *alpha, const float *xVal, const int *xInd, float *y, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseDaxpyi(hipsparseHandle_t handle, int nnz, const double *alpha, const double *xVal, const int *xInd, double *y, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseCaxpyi(hipsparseHandle_t handle, int nnz, const hipComplex *alpha, const hipComplex *xVal, const int *xInd, hipComplex *y, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseZaxpyi(hipsparseHandle_t handle, int nnz, const hipDoubleComplex *alpha, const hipDoubleComplex *xVal, const int *xInd, hipDoubleComplex *y, hipsparseIndexBase_t idxBase)#

Scale a sparse vector and add it to a dense vector.

hipsparseXaxpyi multiplies the sparse vector $$x$$ with scalar $$\alpha$$ and adds the result to the dense vector $$y$$, such that

$y := y + \alpha \cdot x$

for(i = 0; i < nnz; ++i)
{
y[x_ind[i]] = y[x_ind[i]] + alpha * x_val[i];
}


Example
// Number of non-zeros of the sparse vector
int nnz = 3;

// Sparse index vector
int hx_ind[3] = {0, 3, 5};

// Sparse value vector
double hx_val[3] = {1.0, 2.0, 3.0};

// Dense vector
double hy[9] = {1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0};

// Scalar alpha
double alpha = 3.7;

// Index base
hipsparseIndexBase_t idx_base = HIPSPARSE_INDEX_BASE_ZERO;

int* dx_ind;
double*        dx_val;
double*        dy;

hipMalloc((void**)&dx_ind, sizeof(int) * nnz);
hipMalloc((void**)&dx_val, sizeof(double) * nnz);
hipMalloc((void**)&dy, sizeof(double) * 9);

hipMemcpy(dx_ind, hx_ind, sizeof(int) * nnz, hipMemcpyHostToDevice);
hipMemcpy(dx_val, hx_val, sizeof(double) * nnz, hipMemcpyHostToDevice);
hipMemcpy(dy, hy, sizeof(double) * 9, hipMemcpyHostToDevice);

// hipSPARSE handle
hipsparseHandle_t handle;
hipsparseCreate(&handle);

// Call daxpyi to perform y = y + alpha * x
hipsparseDaxpyi(handle, nnz, &alpha, dx_val, dx_ind, dy, idx_base);

// Copy result back to host
hipMemcpy(hy, dy, sizeof(double) * 9, hipMemcpyDeviceToHost);

// Clear hipSPARSE
hipsparseDestroy(handle);

// Clear device memory
hipFree(dx_ind);
hipFree(dx_val);
hipFree(dy);


Note

This function is non blocking and executed asynchronously with respect to the host. It may return before the actual computation has finished.

## hipsparseXdoti()#

hipsparseStatus_t hipsparseSdoti(hipsparseHandle_t handle, int nnz, const float *xVal, const int *xInd, const float *y, float *result, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseDdoti(hipsparseHandle_t handle, int nnz, const double *xVal, const int *xInd, const double *y, double *result, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseCdoti(hipsparseHandle_t handle, int nnz, const hipComplex *xVal, const int *xInd, const hipComplex *y, hipComplex *result, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseZdoti(hipsparseHandle_t handle, int nnz, const hipDoubleComplex *xVal, const int *xInd, const hipDoubleComplex *y, hipDoubleComplex *result, hipsparseIndexBase_t idxBase)#

Compute the dot product of a sparse vector with a dense vector.

hipsparseXdoti computes the dot product of the sparse vector $$x$$ with the dense vector $$y$$, such that

$\text{result} := y^T x$

for(i = 0; i < nnz; ++i)
{
result += x_val[i] * y[x_ind[i]];
}


Example
// Number of non-zeros of the sparse vector
int nnz = 3;

// Sparse index vector
int hx_ind[3] = {0, 3, 5};

// Sparse value vector
float hx_val[3] = {1.0f, 2.0f, 3.0f};

// Dense vector
float hy[9] = {1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f, 9.0f};

// Index base
hipsparseIndexBase_t idx_base = HIPSPARSE_INDEX_BASE_ZERO;

int* dx_ind;
float*        dx_val;
float*        dy;

hipMalloc((void**)&dx_ind, sizeof(int) * nnz);
hipMalloc((void**)&dx_val, sizeof(float) * nnz);
hipMalloc((void**)&dy, sizeof(float) * 9);

hipMemcpy(dx_ind, hx_ind, sizeof(int) * nnz, hipMemcpyHostToDevice);
hipMemcpy(dx_val, hx_val, sizeof(float) * nnz, hipMemcpyHostToDevice);
hipMemcpy(dy, hy, sizeof(float) * 9, hipMemcpyHostToDevice);

// hipSPARSE handle
hipsparseHandle_t handle;
hipsparseCreate(&handle);

// Call sdoti to compute the dot product
float dot;
hipsparseSdoti(handle, nnz, dx_val, dx_ind, dy, &dot, idx_base);

// Clear hipSPARSE
hipsparseDestroy(handle);

// Clear device memory
hipFree(dx_ind);
hipFree(dx_val);
hipFree(dy);


Note

This function is non blocking and executed asynchronously with respect to the host. It may return before the actual computation has finished.

## hipsparseXdotci()#

hipsparseStatus_t hipsparseCdotci(hipsparseHandle_t handle, int nnz, const hipComplex *xVal, const int *xInd, const hipComplex *y, hipComplex *result, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseZdotci(hipsparseHandle_t handle, int nnz, const hipDoubleComplex *xVal, const int *xInd, const hipDoubleComplex *y, hipDoubleComplex *result, hipsparseIndexBase_t idxBase)#

Compute the dot product of a complex conjugate sparse vector with a dense vector.

hipsparseXdotci computes the dot product of the complex conjugate sparse vector $$x$$ with the dense vector $$y$$, such that

$\text{result} := \bar{x}^H y$

for(i = 0; i < nnz; ++i)
{
result += conj(x_val[i]) * y[x_ind[i]];
}


Note

This function is non blocking and executed asynchronously with respect to the host. It may return before the actual computation has finished.

## hipsparseXgthr()#

hipsparseStatus_t hipsparseSgthr(hipsparseHandle_t handle, int nnz, const float *y, float *xVal, const int *xInd, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseDgthr(hipsparseHandle_t handle, int nnz, const double *y, double *xVal, const int *xInd, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseCgthr(hipsparseHandle_t handle, int nnz, const hipComplex *y, hipComplex *xVal, const int *xInd, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseZgthr(hipsparseHandle_t handle, int nnz, const hipDoubleComplex *y, hipDoubleComplex *xVal, const int *xInd, hipsparseIndexBase_t idxBase)#

Gather elements from a dense vector and store them into a sparse vector.

hipsparseXgthr gathers the elements that are listed in x_ind from the dense vector $$y$$ and stores them in the sparse vector $$x$$.

for(i = 0; i < nnz; ++i)
{
x_val[i] = y[x_ind[i]];
}


Example
// Number of non-zeros of the sparse vector
int nnz = 3;

// Sparse index vector
int hx_ind[3] = {0, 3, 5};

// Sparse value vector
float hx_val[3];

// Dense vector
float hy[9] = {1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0};

// Index base
hipsparseIndexBase_t idx_base = HIPSPARSE_INDEX_BASE_ZERO;

int* dx_ind;
float*         dx_val;
float*         dy;

hipMalloc((void**)&dx_ind, sizeof(int) * nnz);
hipMalloc((void**)&dx_val, sizeof(float) * nnz);
hipMalloc((void**)&dy, sizeof(float) * 9);

hipMemcpy(dx_ind, hx_ind, sizeof(int) * nnz, hipMemcpyHostToDevice);
hipMemcpy(dy, hy, sizeof(float) * 9, hipMemcpyHostToDevice);

// hipSPARSE handle
hipsparseHandle_t handle;
hipsparseCreate(&handle);

// Call sgthr
hipsparseSgthr(handle, nnz, dy, dx_val, dx_ind, idx_base);

// Copy result back to host
hipMemcpy(hx_val, dx_val, sizeof(float) * nnz, hipMemcpyDeviceToHost);

// Clear hipSPARSE
hipsparseDestroy(handle);

// Clear device memory
hipFree(dx_ind);
hipFree(dx_val);
hipFree(dy);


Note

This function is non blocking and executed asynchronously with respect to the host. It may return before the actual computation has finished.

## hipsparseXgthrz()#

hipsparseStatus_t hipsparseSgthrz(hipsparseHandle_t handle, int nnz, float *y, float *xVal, const int *xInd, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseDgthrz(hipsparseHandle_t handle, int nnz, double *y, double *xVal, const int *xInd, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseCgthrz(hipsparseHandle_t handle, int nnz, hipComplex *y, hipComplex *xVal, const int *xInd, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseZgthrz(hipsparseHandle_t handle, int nnz, hipDoubleComplex *y, hipDoubleComplex *xVal, const int *xInd, hipsparseIndexBase_t idxBase)#

Gather and zero out elements from a dense vector and store them into a sparse vector.

hipsparseXgthrz gathers the elements that are listed in x_ind from the dense vector $$y$$ and stores them in the sparse vector $$x$$. The gathered elements in $$y$$ are replaced by zero.

for(i = 0; i < nnz; ++i)
{
x_val[i]    = y[x_ind[i]];
y[x_ind[i]] = 0;
}


Note

This function is non blocking and executed asynchronously with respect to the host. It may return before the actual computation has finished.

## hipsparseXroti()#

hipsparseStatus_t hipsparseSroti(hipsparseHandle_t handle, int nnz, float *xVal, const int *xInd, float *y, const float *c, const float *s, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseDroti(hipsparseHandle_t handle, int nnz, double *xVal, const int *xInd, double *y, const double *c, const double *s, hipsparseIndexBase_t idxBase)#

Apply Givens rotation to a dense and a sparse vector.

hipsparseXroti applies the Givens rotation matrix $$G$$ to the sparse vector $$x$$ and the dense vector $$y$$, where

$\begin{split} G = \begin{pmatrix} c & s \\ -s & c \end{pmatrix} \end{split}$

for(i = 0; i < nnz; ++i)
{
x_tmp = x_val[i];
y_tmp = y[x_ind[i]];

x_val[i]    = c * x_tmp + s * y_tmp;
y[x_ind[i]] = c * y_tmp - s * x_tmp;
}


Example
// Number of non-zeros of the sparse vector
int nnz = 3;

// Sparse index vector
int hx_ind[3] = {0, 3, 5};

// Sparse value vector
float hx_val[3] = {1.0f, 2.0f, 3.0f};

// Dense vector
float hy[9] = {1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f, 9.0f};

// c and s
float c = 3.7;
float s = 1.3;

// Index base
hipsparseIndexBase_t idx_base = HIPSPARSE_INDEX_BASE_ZERO;

int* dx_ind;
float*        dx_val;
float*        dy;

hipMalloc((void**)&dx_ind, sizeof(int) * nnz);
hipMalloc((void**)&dx_val, sizeof(float) * nnz);
hipMalloc((void**)&dy, sizeof(float) * 9);

hipMemcpy(dx_ind, hx_ind, sizeof(int) * nnz, hipMemcpyHostToDevice);
hipMemcpy(dx_val, hx_val, sizeof(float) * nnz, hipMemcpyHostToDevice);
hipMemcpy(dy, hy, sizeof(float) * 9, hipMemcpyHostToDevice);

// hipSPARSE handle
hipsparseHandle_t handle;
hipsparseCreate(&handle);

// Call sroti
hipsparseSroti(handle, nnz, dx_val, dx_ind, dy, &c, &s, idx_base);

// Copy result back to host
hipMemcpy(hx_val, dx_val, sizeof(float) * nnz, hipMemcpyDeviceToHost);
hipMemcpy(hy, dy, sizeof(float) * 9, hipMemcpyDeviceToHost);

// Clear hipSPARSE
hipsparseDestroy(handle);

// Clear device memory
hipFree(dx_ind);
hipFree(dx_val);
hipFree(dy);


Note

This function is non blocking and executed asynchronously with respect to the host. It may return before the actual computation has finished.

## hipsparseXsctr()#

hipsparseStatus_t hipsparseSsctr(hipsparseHandle_t handle, int nnz, const float *xVal, const int *xInd, float *y, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseDsctr(hipsparseHandle_t handle, int nnz, const double *xVal, const int *xInd, double *y, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseCsctr(hipsparseHandle_t handle, int nnz, const hipComplex *xVal, const int *xInd, hipComplex *y, hipsparseIndexBase_t idxBase)#
hipsparseStatus_t hipsparseZsctr(hipsparseHandle_t handle, int nnz, const hipDoubleComplex *xVal, const int *xInd, hipDoubleComplex *y, hipsparseIndexBase_t idxBase)#

Scatter elements from a dense vector across a sparse vector.

hipsparseXsctr scatters the elements that are listed in x_ind from the sparse vector $$x$$ into the dense vector $$y$$. Indices of $$y$$ that are not listed in x_ind remain unchanged.

for(i = 0; i < nnz; ++i)
{
y[x_ind[i]] = x_val[i];
}


Example
// Number of non-zeros of the sparse vector
int nnz = 3;

// Sparse index vector
int hx_ind[3] = {0, 3, 5};

// Sparse value vector
float hx_val[3] = {9.0, 2.0, 3.0};

// Dense vector
float hy[9] = {1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0};

// Index base
hipsparseIndexBase_t idx_base = HIPSPARSE_INDEX_BASE_ZERO;

int* dx_ind;
float*         dx_val;
float*         dy;

hipMalloc((void**)&dx_ind, sizeof(int) * nnz);
hipMalloc((void**)&dx_val, sizeof(float) * nnz);
hipMalloc((void**)&dy, sizeof(float) * 9);

hipMemcpy(dx_ind, hx_ind, sizeof(int) * nnz, hipMemcpyHostToDevice);
hipMemcpy(dx_val, hx_val, sizeof(float) * nnz, hipMemcpyHostToDevice);
hipMemcpy(dy, hy, sizeof(float) * 9, hipMemcpyHostToDevice);

// hipSPARSE handle
hipsparseHandle_t handle;
hipsparseCreate(&handle);

// Call ssctr
hipsparseSsctr(handle, nnz, dx_val, dx_ind, dy, idx_base);

// Copy result back to host
hipMemcpy(hy, dy, sizeof(float) * 9, hipMemcpyDeviceToHost);

// Clear hipSPARSE
hipsparseDestroy(handle);

// Clear device memory
hipFree(dx_ind);
hipFree(dx_val);
hipFree(dy);


Note

This function is non blocking and executed asynchronously with respect to the host. It may return before the actual computation has finished.