# RI

Parameters influencing resolution of the identity (RI) that is used in RI-MP2, RI-RPA, RI-SOS-MP2 and GW (inside RI-RPA). [Edit on GitHub]

Subsections

- OPT_RI_BASIS
- RI_METRIC

## Keywords

- CALC_COND_NUM

- COL_BLOCK

- DO_SVD

- EPS_SVD

- ERI_BLKSIZE

- ROW_BLOCK

## Keyword descriptions

CALC_COND_NUM: logical = F

  Aliases: CALC_CONDITION_NUMBER

  Lone keyword: `T`

  Usage: CALC_COND_NUM

  Calculate the condition number of the (P|Q) matrix for the RI methods. [Edit on GitHub]

COL_BLOCK: integer = -1

  Aliases: COL_BLOCK_SIZE

  Usage: COL_BLOCK 512

  Size of the column block used in the SCALAPACK block cyclic data distribution. Default is (COL_BLOCK=-1) is automatic. A proper choice can speedup the parallel matrix multiplication in the case of RI-RPA and RI-SOS-MP2-Laplace. [Edit on GitHub]

DO_SVD: logical = F

  Lone keyword: `T`

  Usage: DO_SVD .TRUE.

  Wether to perform a singular value decomposition instead of the Cholesky decomposition of the potential operator in the RI basis. Computationally expensive but numerically more stable. It reduces the computational costs of some subsequent steps. Recommended when a longrange Coulomb potential is employed. [Edit on GitHub]

EPS_SVD: real = 0.00000000E+000

  Usage: EPS_SVD 1E-5

  Determines the upper bound of eigenvectors to be removed during the SVD (see DO_SVD). [Edit on GitHub]

ERI_BLKSIZE: integer[2] = 4 16

  Usage: ERI_BLKSIZE

  block sizes for tensors (only used if ERI_METHOD=MME). First value is the block size for ORB basis, second value is the block size for RI_AUX basis. [Edit on GitHub]

ROW_BLOCK: integer = -1

  Aliases: ROW_BLOCK_SIZE

  Usage: ROW_BLOCK 512

  Size of the row block used in the SCALAPACK block cyclic data distribution. Default is (ROW_BLOCK=-1) is automatic. A proper choice can speedup the parallel matrix multiplication in the case of RI-RPA and RI-SOS-MP2-Laplace. [Edit on GitHub]