Exchange#

cuest.bindings.cuestDFSymmetricExchangeComputeWorkspaceQuery(
*,
handle: cuest.bindings.cuest.cuestHandle,
plan: cuest.bindings.cuest.cuestDFIntPlanHandle,
parameters: cuest.bindings.cuest.Parameters,
variableBufferSize: int,
temporaryWorkspaceDescriptor: int,
numOccupied: int,
coefficientMatrix: cuest.bindings.cuest.Pointer,
outExchangeMatrix: cuest.bindings.cuest.Pointer,
) → cuest.bindings.cuest.CuestStatus#

Query the temporary workspace required (in bytes) for a DF exchange matrix calculation.

This function returns (via output parameters) the host and device workspace buffer sizes needed to perform a symmetric exchange computation, given the plan and matrix dimensions. The coefficient matrix and output buffer may be NULL (only sizes are computed).

Parameters#

handle[in]CuestHandle

cuEST handle. Must not be NULL.

plan[in]CuestDFIntPlanHandle

Density-fitted integral plan (opaque handle).

parameters[in]cuestDFSymmetricExchangeComputeParameters_t

Parameters object. Must not be NULL.

variableBufferSize[in]WorkspaceDescriptor

User-provided descriptor for an internal scratch buffer (host and device). Must not be NULL. For most problem sizes, 2 GB is a good buffer size. On newer devices, such as H200 and B200, buffer sizes up to 8 GB may improve performance. Host memory is currently unused. Note that the variableBufferSize does not limit total memory usage. This value must remain unchanged between WorkspaceQuery and Compute calls.

temporaryWorkspaceDescriptor[out]WorkspaceDescriptor

Output descriptor for workspace sizes (host and device). Must not be NULL.

numOccupied[in]int

Number of occupied orbitals (rows in coefficient matrix); must be greater than zero.

coefficientMatrix[in]Pointer

Optional pointer to coefficient matrix buffer. May be NULL.

outExchangeMatrix[in]Pointer

Optional pointer to output exchange matrix buffer. May be NULL.

Returns#

status[out]cuestStatus_t
cuest.bindings.cuestDFSymmetricExchangeCompute(
*,
handle: cuest.bindings.cuest.cuestHandle,
plan: cuest.bindings.cuest.cuestDFIntPlanHandle,
parameters: cuest.bindings.cuest.Parameters,
variableBufferSize: int,
temporaryWorkspace: int,
numOccupied: int,
coefficientMatrix: cuest.bindings.cuest.Pointer,
outExchangeMatrix: cuest.bindings.cuest.Pointer,
) → cuest.bindings.cuest.CuestStatus#

Compute the AO symmetric exchange (K) matrix using density fitting (DF) with the supplied DF integral plan and coefficient matrix.

This function computes the density-fitted AO exchange matrix from an orbital coefficient matrix and a DF plan.

  • The input coefficient matrix must be preallocated to size (numOccupied × nao). Data is expected to be in row-major format.

  • The output buffer outExchangeMatrix must be preallocated for (nao × nao) doubles.

  • All handles, pointers, and buffers must be valid and non-NULL.

  • Temporary workspace must be preallocated using size returned by cuestDFSymmetricExchangeComputeWorkspaceQuery().

Parameters#

handle[in]CuestHandle

cuEST handle. Must not be NULL.

plan[in]CuestDFIntPlanHandle

Density-fitted integral plan (opaque handle).

parameters[in]cuestDFSymmetricExchangeComputeParameters_t

Parameters object. Must not be NULL.

variableBufferSize[in]WorkspaceDescriptor

User-provided descriptor for an internal scratch buffer (host and device). Must not be NULL. For most problem sizes, 2 GB is a good buffer size. On newer devices, such as H200 and B200, buffer sizes up to 8 GB may improve performance. Host memory is currently unused. Note that the variableBufferSize does not limit total memory usage. This value must remain unchanged between WorkspaceQuery and Compute calls.

temporaryWorkspace[in]Workspace

Temporary workspace buffer for this operation. Must not be NULL.

numOccupied[in]int

Number of occupied orbitals (rows in coefficient matrix); must be greater than zero.

coefficientMatrix[in]Pointer

Input coefficient matrix (size: numOccupied × nao) on the GPU. Must not be NULL.

outExchangeMatrix[out]Pointer

Output buffer for the AO exchange matrix (size: nao × nao) on the GPU. Must not be NULL. Elements of this array are overwritten by the calculation results.

Returns#

status[out]cuestStatus_t