Changeset 6fd8de0 in sasmodels for doc/developer


Ignore:
Timestamp:
Mar 22, 2016 5:28:16 AM (9 years ago)
Author:
wojciech
Branches:
master, core_shell_microgels, costrafo411, magnetic_model, release_v0.94, release_v0.95, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests
Children:
69aa451
Parents:
fec69dd
Message:

Updated polydispersity loop documentation

File:
1 edited

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  • doc/developer/calculator.rst

    r48fbd50 r6fd8de0  
    77- KERNEL declares a function to be available externally 
    88- KERNEL_NAME is the name of the function being declared 
    9 - MAX_PD is the maximum depth of the polydispersity loop 
     9- MAX_PD is the maximum depth of the polydispersity loop [model specific] 
    1010- NPARS is the number of parameters in the kernel 
    1111- PARAMETER_TABLE is the declaration of the parameters to the kernel:: 
    … …  
    3030        double sld_solvent 
    3131 
    32 - CALL_IQ(q, i, pars) is the declaration of a call to the kernel:: 
     32- CALL_IQ(q, i, var) is the declaration of a call to the kernel:: 
    3333 
    3434    Cylinder: 
    … …  
    7272    BarBell: 
    7373 
    74         #define INVALID(var) (var.bell_radius > var.radius) 
     74        #define INVALID(var) (var.bell_radius < var.radius) 
    7575 
    7676    Model with complicated constraints: 
    … …  
    9090    0: scale        {scl = constant} 
    9191    1: background   {bkg = constant} 
    92     5: length       {l = vector of 30pts} 
    93     4: radius       {r = vector of 10pts} 
    94     3: sld          {s = constant/(radius**2*length)} 
    95     2: sld_solvent  {s2 = constant} 
     92    2: length       {l = vector of 30pts} 
     93    3: radius       {r = vector of 10pts} 
     94    4: sld          {s = constant/(radius**2*length)} 
     95    5: sld_solvent  {s2 = constant} 
    9696 
    9797This generates the following call to the kernel (where x stands for an 
    … …  
    100100    NPARS = 4  // scale and background are in all models 
    101101    problem { 
    102         pd_par = {5, 4, x, x}         // parameters *radius* and *length* vary 
     102        pd_par = {3, 2, x, x}         // parameters *radius* and *length* vary 
    103103        pd_length = {30, 10, 0, 0}    // *length* has more, so it is first 
    104104        pd_offset = {10, 0, x, x}     // *length* starts at index 10 in weights 
    105105        pd_stride = {1, 30, 300, 300} // cumulative product of pd length 
    106         pd_isvol = {1, 1, x, x}       // true if weight is a volume weight 
     106        pd_isvol = {True, True, x, x}       // true if weight is a volume weight 
    107107        par_offset = {2, 3, 303, 313}  // parameter offsets 
    108108        par_coord = {0, 3, 2, 1} // bitmap of parameter dependencies 
    109         fast_coord_index = {5, 3, x, x} 
     109        fast_coord_index = {3, 5, x, x} // radius and sld have fast index 
    110110        fast_coord_count = 2  // two parameters vary with *length* distribution 
    111111        theta_var = -1   // no spherical correction 
    … …  
    113113    } 
    114114 
    115     weight = { l0, .., l29, r0, .., r9} 
     115    weight = { l0, .., l29, r0, .., r9} //length comes first as the longest vec 
    116116    pars = { scl, bkg, l0, ..., l29, r0, r1, ..., r9, 
    117117             s[l0,r0], ... s[l0,r9], s[l1,r0], ... s[l29,r9] , s2} 
     118             //where s[x,y] stands for material sld, s2 = solvent sld 
    118119 
    119120    nq = 130 
    … …  
    125126indices, one for each polydisperse parameter, stored in pd_par[n]. 
    126127Non-polydisperse parameters do not appear in this array. Each polydisperse 
    127 parameter has a weight vector whose length is stored in pd_length[n], 
     128parameter has a weight vector whose length is stored in pd_length[n]. 
    128129The weights are stored in a contiguous vector of weights for all 
    129130parameters, with the starting position for the each parameter stored 
    … …  
    150151parameter are arranged contiguously in a vector, with offset[k] giving the 
    151152starting location of parameter k in the vector.  Each parameter defines 
    152 coord[k] as a bit mask indicating which polydispersity parameters the 
     153par_coord[k] as a bit mask indicating which polydispersity parameters the 
    153154parameter depends upon. Usually this is zero, indicating that the parameter 
    154155is independent, but for the cylinder example given, the bits for the 
    … …  
    207208in order to preserve the 'surface area' of the weight distribution. 
    208209 
    209 TODO: cutoff 
     210cutoff parameter limits integration area within polydispersity hypercude, 
     211which speeds calculations 
    210212 
    211213For accuracy we may want to introduce Kahan summation into the integration:: 
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