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Tensor Network Theory Library
Beta release 1.1.0
A library of routines for performing TNT-based operations
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Tensor Network Theory Library
Beta release 1.1.0
A library of routines for performing TNT-based operations
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The system has several global parameters that are used in all calculations. These can be based on the physical properties of your system, e.g. setting the basis operator and the global physical symmetries. In addition some of these are related to values used during calculations, for examples tolerances used in the SVD.
Functions | |
| void | tntFinalize (void) |
| void | tntInitialize (void) |
| void | tntMaxEigIterSet (int maxnum) |
| void | tntReshapeReuseDisable (void) |
| double | tntSVDRelTruncTolGet (void) |
| void | tntSVDRelTruncTolSet (double relTruncTol) |
| void | tntSVDRoutineSet (int svdtype) |
| double | tntSVDTolGet (void) |
| void | tntSVDTolSet (double inpTOL) |
| double | tntSVDTruncTolGet (void) |
| void | tntSVDTruncTolSet (double truncTol) |
| unsigned | tntSymmNumGet (void) |
| int | tntSymmTypeGet (void) |
| void | tntSymmTypeSet (const char *symmTypeStr, unsigned num_qn) |
| void | tntSymmTypeUnset (void) |
| void | tntSysBasisOpFree (void) |
| tntNode | tntSysBasisOpGet (void) |
| void | tntSysBasisOpSet (tntNode basisOp) |
| int | tntSysTypeGet (void) |
| void | tntSysTypeSet (int sysnum) |
| void | tntTruncType (const char *funcname) |
Variables | |
| tntSystem | systype |
| void tntFinalize | ( | void | ) |
| void tntInitialize | ( | void | ) |
| void tntMaxEigIterSet | ( | int | maxnum | ) |
| void tntReshapeReuseDisable | ( | void | ) |
Disables the storage of the translations done in the reshape component. This will conserve memory but typically at a great expense computationally. It is recommended to use this function when the size of the tensors is constantly changing, for example in cases where the tolerance is set for the minimum size singular value to keep using tntSVDTruncTolSet().
| double tntSVDRelTruncTolGet | ( | void | ) |
Use this function to get the relative minimum for the singular values that will be kept in the SVD. Any singluar values which are `truncTol' times smaller than the maximum singluar value are be discarded, along with their associated right and left singular vectors. A negative value means that all singular values up to the value \(\chi\) are kept.
| void tntSVDRelTruncTolSet | ( | double | relTruncTol | ) |
Use this function to set a relative minimum for the singular values that will be kept in the SVD. Any singluar values which are `truncTol' times smaller than the maximum singluar value will be discarded, along with their associated right and left singluar vectors. Set to a negative value to ensure that all singular values up to the value \(\chi\) are kept (unless an absolute value has also been set).
Calling this function sets the tolerance for all subsequent SVDs. It is set to a negative value by default i.e. all singular values kept.
| relTruncTol | The chosen tolerance. |
| void tntSVDRoutineSet | ( | int | svdtype | ) |
Use this function to change the SVD routine used in the core library. By default the LAPACK divide and conquer SVD is used (TNT_LAPACK_SDD). If you are having issues with the SVD converging or accuracy, please try using the LAPACK standard SVD (TNT_LAPACK_SVD). This performs more slowly but we have found it to be better behaved.
| svdtype | The chose SVD type. Allowed values are TNT_LAPACK_SDD and TNT_LAPACK_SVD. |
| double tntSVDTolGet | ( | void | ) |
Get the tolerance below which values are treated as zero in the SVD.
| void tntSVDTolSet | ( | double | inpTOL | ) |
Sets the tolerance below which values are treated as zero in the SVD
| inpTOL | The chosen tolerance. |
| double tntSVDTruncTolGet | ( | void | ) |
Use this function to get the absolute minimum for the singular values that will be kept in the SVD. Any singluar values which are smaller than `truncTol' will be discarded, along with their associated right and left singluar vectors. A negative value means that all singular values up to the value \(\chi\) are kept.
| void tntSVDTruncTolSet | ( | double | truncTol | ) |
Use this function to set an absolute minimum for the singular values that will be kept in the SVD. Any singluar values which are smaller than `truncTol' will be discarded, along with their associated right and left singluar vectors. Set to a negative value to ensure that all singular values up to the value \(\chi\) are kept (unless a relative value has also been set).
Calling this function sets the tolerance for all subsequent SVDs. It is set to a negative value by default i.e. all singular values kept. However, if there are any parts of your algorithm that take the inverse of nodes that result from an SVD, it is recommended to set this value (e.g. to 1e-8) to ensure that your matrices are not singular.
| truncTol | The chosen tolerance. |
| unsigned tntSymmNumGet | ( | void | ) |
Gets the number of seperate conserved quantities, or the number of quantum numbers required for a quantum number labels e.g for an two-species system will return 2. The return value will be zero if no symmetry type is set.
| int tntSymmTypeGet | ( | void | ) |
Gets the symmetry type for the system, returning the result as an integer code more than 1, which will be one of the allowed symmetry types given by the defined variables. The return value will be TNT_SYMM_NONE if no symmetry type is set.
In the current version, the only currently allowed value is TNT_SYMM_U1.
| void tntSymmTypeSet | ( | const char * | symmTypeStr, |
| unsigned | num_qn | ||
| ) |
Sets the symmetry type for the system. If it is set, then quantum number information is tracked, and the releavant quantities are conserved.
For example if U(1) is set (tntSymmetrySet("U(1)")), and spin or boson operators created using tntMpsCreateSpinOp and tntMpsCreateBosonOp, and wave functions created using tntMpsCreateRandom() or tntMpsCreateConfig(), they will be set up to ensure that the total z-projection of spin or boson number are conserved respectively. This can significantly speed up calculations.
The argument num_qn sets the number of seperate conserved quantities e.g. set to 2 for a two species system where the number of species 1 and the number of species 2 is conserved.
| symmTypeStr | String denoting the symmetry type e.g. "U(1)". |
| num_qn | Number of separate conserved quantities. |
| void tntSymmTypeUnset | ( | void | ) |
Turns off keeping track of symmetries in the system. The quantum number information is removed from the basis operator, and library functions will no longer enforce number conservation.
Note that nodes that are in the blocked or symmetric format will be converted to VALS structure as they are encountered by library functions, rather than as soon as this function is called.
Note also that the SVD tolerance for zeroing values is turned back on to the default value of TNT_DEFAULT_TOL.
If symmetry information is not turned on prior to calling this function, it will have to effect.
| void tntSysBasisOpFree | ( | void | ) |
| tntNode tntSysBasisOpGet | ( | void | ) |
Returns the operator which defines the physical basis for the system. Note that this returns the handle to the actual basis operator, rather than a copy of it, so any modifications to it will alter the basis operator for the entire system. Therefore we recommend only inspecting properties of the operator rather than making changes to it unless you know exactly what you are doing.
| void tntSysBasisOpSet | ( | tntNode | basisOp | ) |
Sets the operator which defines the physical basis for the system. Note that a copy of the supplied node basisOp is taken, so any changes can be made to basisOp after the function has been called will not affect the system basis operator. Instead use tntSysBasisOpGet() to get a handle to the basis operator after this function has been called.
| basisOp | Node that defines the basis operator |
| int tntSysTypeGet | ( | void | ) |
Returns a number which defines the type of system, where definitions for these numbers are given in the header file for the tier 2 library being used. Currently the only tier 2 library is libtntMps, which can give the values TNT_MPS_SPIN and TNT_MPS_BOSON.
| void tntSysTypeSet | ( | int | sysnum | ) |
Sets the system type using the integer code given. Note that no checks are made that the integer given actually corresponds to a system type known by the tier 2 library - users can define custom system types if they wish.
See the header or documentation for your tier 2 library for the currently supported system types. Currently the only tier 2 library is libtntMps, which can give the values TNT_MPS_SPIN and TNT_MPS_BOSON.
| sysnum | Number code defining the system type. |
| void tntTruncType | ( | const char * | funcname | ) |
Sets the function used to calculate the truncation error \(e_{\mathrm{trunc}}\) when taking the SVD of a node. Once this function is set the same truncation type will be used for all subsequent calculations, unless it is called again a different argument. Note the choice will automatically be saved to any output file, and reloaded when that file is loaded. The currently supported truncation types are:
'sumsquares'
The error is given by the sum of the squares of the discarded singluar values i.e.
\[ e_{\mathrm{trunc}} = \sum_{j=\chi}^{\chi_{\mathrm{orig}}-1} |S_{j}|^2. \]
'1norm'
The error is given by the 1-norm of the discarded singluar values i.e.
\[ e_{\mathrm{trunc}} = \sum_{j=\chi}^{\chi_{\mathrm{orig}}-1} |S_{j}|. \]
'1normscaled'
The error is given by the 1-norm of the discarded singluar values divided by the 1-norm of all the singular values i.e.
\[ e_{\mathrm{trunc}} = \left( \sum_{j=\chi}^{\chi_{\mathrm{orig}}-1} |S_{j}| \right)\Bigg{/}\left( \sum_{j=0}^{\chi_{\mathrm{orig}}-1} |S_{j}| \right). \]
'2norm'
The the error \(e\) is given by the 2-norm of the discarded singluar values i.e.
\[ e_{\mathrm{trunc}} = \left( \sum_{j=\chi}^{\chi_{\mathrm{orig}}-1} |S_{j}|^2 \right)^{1/2}. \]
'2normscaled'
The error \(e\) is given by the 2-norm of the discarded singluar values divided by the 2-norm of all the singular values i.e.
\[ e_{\mathrm{trunc}} = \left( \sum_{j=\chi}^{\chi_{\mathrm{orig}}-1} |S_{j}|^2 \right)^{1/2}\Bigg{/}\left( \sum_{j=0}^{\chi_{\mathrm{orig}}-1} |S_{j}|^2 \right)^{1/2}. \]
In all the above cases, the indexing in the sum starts from zero. The default is '2norm', and will be used if no value is set using this function.
| funcname | The name of desired truncation type e.g. "sumsquares". |
1.8.6