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Introduction to sparsediag

The sparsediag is an exact diagonalization program in ALPS, using the Lanczos algorithm of the IETL library to compute low-lying eigestates of the Hamiltonian. Hence, it can be used for computing ground-state properties of any model that can be defined using the ALPS libraries. The main limitation is one of size, i.e., memory and CPU time may become unacceptable at sizes where other, more specialized applications still work well.

Running a computation

is discussed in the sparsediag tutorial.

Input parameters

In addition to the input parameters are explained here the sparsediag code takes the following parameter:

Parameter Default Meaning
NUMBER_EIGENVALUES 1 the number of low-lying eigenstates to be calculated


The license allows the use of the applications for non-commercial scientific use provided that the use of the ALPS applications and libraries is acknowledged and referenced in any scientific publication, as discussed in this license file.

Questions and request for support

can be addressed to the ALPS user mailing list at We appreciate hearing your requests for additional features and also welcome any contributions to the ALPS project.